Landscape Message: June 4, 2021

UMass Extension's Landscape Message is an educational newsletter intended to inform and guide Massachusetts Green Industry professionals in the management of our collective landscape. Detailed reports from scouts and Extension specialists on growing conditions, pest activity, and cultural practices for the management of woody ornamentals, trees, and turf are regular features. The following issue has been updated to provide timely management information and the latest regional news and environmental data.

The Landscape Message will be updated weekly in June. The next message will be posted on June 11. To receive immediate notification when the next Landscape Message update is posted, be sure to join our e-mail list 

To read individual sections of the message, click on the section headings below to expand the content:

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Scouting Information by Region

Environmental Data

The following data was collected on or about June 2, 2021. Total accumulated growing degree days (GDD) represent the heating units above a 50° F baseline temperature collected via regional NEWA stations for the 2021 calendar year. This information is intended for use as a guide for monitoring the developmental stages of pests in your location and planning management strategies accordingly.

MA Region/Location	GDD		Soil Temp (°F at 4" depth)		Precipitation (1-Week Gain)	Time/Date of Readings
	1-Week Gain	2021 Total	Sun	Shade
CAPE	58.5	296.5	62	56	2.75	12:00 PM 6/2
SOUTHEAST	56	336	78	61	2.44	2:00 PM 6/2
NORTH SHORE	68.5	402.5	58	54	2.20	10:00 AM 6/2
EAST	57	408.5	58	53	3.00	4:00 PM 6/2
METRO	56.5	383	56	54	3.05	6:00 AM 6/2
CENTRAL	54	396.5	62	57	4.38	7:00 AM 6/2
PIONEER VALLEY	50	392	60	56	2.66	10:30 AM 6/2
BERKSHIRES	30.5	277.5	58	54	2.48	6:30 AM 6/2
AVERAGE	54	362	62	56	2.87	_
n/a = information not available

Check the drought status as of 6/1 here: https://droughtmonitor.unl.edu/CurrentMap/StateDroughtMonitor.aspx?MA

Current municipal water restrictions are shown on this map:  https://www.mass.gov/doc/water-use-restrictions-map/download

Phenology

Indicator Plants - Stages of Flowering (BEGIN, BEGIN/FULL, FULL, FULL/END, END)
PLANT NAME (Botanic/ Common)	CAPE	S.E.	N.S.	EAST	METRO W.	CENT.	P.V.	BERK.
Kalmia latifolia (mountain laurel)	Begin	Full	Begin	Begin	Begin	Begin	Begin/Full	*
Cotinus coggygria (common smokebush)	Begin	Begin/Full	Begin	Begin	Begin	Begin	Begin	*
Weigela florida (old fashioned weigela)	Begin/Full	Full	Begin/Full	Begin	Begin	Begin/Full	Begin/Full	Begin/Full
Robinia pseudoacacia (black locust)	Full	Full/End	Full	Full	Full	Full	Full	Full
Syringa meyeri (Meyer lilac)	Full	Full	Full	Full	*	*	Full	Full
Enkianthus campanulatus (redvein enkianthus)	*	*	Full/End	Full	Full	Full	End	Full
Rhododendron catawbiense (Catawba rhododendron)	Full	Full/End	End	Full	Full	Full/End	Full/End	Full
Deutzia spp. (deutzia species)	Full	Full/End	Full/End	Full	Full/End	Full/End	Full/End	Full/End
Rhododendron carolinianum (Carolina rhododendron)	End	*	End	End	Full/End	Full/End	Full/End	*
Spiraea x vanhouttei (Vanhoutte spirea)	End	End	End	End	Full/End	Full/End	Full/End	Full
Aesculus hippocastanum (common horsechestnut)	End	Full	End	End	End	End	End	End
* = no activity to report/information not available

Regional Notes

Cape Cod Region (Barnstable)

General Conditions: The average temperature for the period from May 26 – June 2 was 58˚F with a high of 78˚F on May 27 and a low of 43˚F on May 29. The period was dominated by the cool, spring like weather that started on May 28 and ended on May 31. On May 29 and 30 the temperature did not go over 50˚F. The four-day stretch was cloudy and cool, with high humidity and precipitation. The rain was much needed, and many locations received around 3 inches, giving the ground a good soaking. The prolonged wetness during leaf development is likely to have some disease implications. The heavy rain and wind have caused many plants with heavy blooms to lodge and many lawns have scattered leaves and twigs. Herbaceous plants seen in bloom during the period include lupine, foxglove, peony, bearded iris, Japanese iris, bloodred geranium, oxeye daisy, painted daisy, fringed bleeding heart, blue false indigo, catmint, and Salvia ‘May Night’. Woody plants seen in bloom during the period include arrowwood viburnum, alternate leaf dogwood, leucothoe, black cherry, kousa dogwood, and some roses.

Pests/Problems: The following insect pests or insect pest damage were seen: some winter moth damage primarily to maples, apple, and blueberry (very few caterpillars can be found so migration to the soil has begun), some intense damage from oak shothole leafminer on white oak, viburnum leaf beetle larvae causing damage on arrowwood viburnum, snowball aphid on arrowwood viburnum, azalea lacebug nymphs on azalea, sphinx moth caterpillar feeding on rhododendron, maple eyespot gall midge on red maple, columbine leafminer on columbine, sawfly larvae feeding on white oak, eriophyid mite on beech and arrowwood viburnum, earwig damage to hydrangea, buddleia, and hardy hibiscus. Not much for disease symptoms and signs this period, just anthracnose on maple and sycamore, foliar disease on white pine and an amazing display of cedar apple rust telial horns on eastern red cedar. Natural leaf drop on American holly is occurring and often misidentified as disease. Invasive plants seen in bloom include burning bush, black swallowwort, autumn olive, and black locust. Weeds in bloom include black medic, yellow wood sorrel, red sorrel, white clover, and buttercups. Deer and dog ticks are active – keep yourself protected. There is a great deal of rabbit activity.

Southeast Region (Dighton)

General Conditions: Be careful what you ask for; the rains I've been begging for arrived over the long weekend and put a damper on both Memorial Day ceremonies and graduation parties. Despite the spoiled festivities, we have a welcome, temporary reprieve from impending drought. Among the many plants I've noticed in flower are the following: Achillea millefolium (common yarrow), A. 'Moonshine', Allium spp. (flowering onion), Aquilegia (columbine), Aesculus hippocastanum (horse chestnut), Baptisia australis (false blue indigo), Calystegia sepium (hedge bindweed), Coreopsis spp. (tickseed), Chionanthus virginicus (white fringetree), Chelidonium majus (greater celandine), Conium maculatum (poison hemlock), Convallaria majalis (lily of the valley), Cotinus coggygria (smoke bush), Cornus kousa (Chinese dogwood), Cytisus scoparius (Scotch broom), Dianthus spp. (pinks), Deutzia, Geranium sanguineum (cranesbill geranium), Hesperis matronalis (dame's rocket), Iris germanica (German iris), I. pseudacorus (yellow flag iris), I. sibirica (Siberian iris), Kalmia latifolia (mountain laurel), Laburnum anagyroides (golden rain tree), Lamprocapnos spectabilis (bleeding heart), Leucanthemum vulgare (oxeye daisy), L. x superbum (shasta daisy), Linnaea amabilis (Kolkwitzia, beauty bush), Lonicera japonica (Japanese honeysuckle), Lunaria annua (honesty), Lupinus (lupine), Medicago lupulina (black medic), Nepeta spp. (catmint), Paeonia officinalis (garden peony), Papaver orientale (oriental poppy), Phlox subulata (creeping phlox), Pilosella (hawkweed), Polygonatum biflorum (Solomon's seal), Potentilla fruticosa (bush cinquefoil), Prunus serotina (black cherry), Rhododendron x catawbiense, R. mollis (Azalea mollis), Robinia pseudoacacia (black locust), Rosa 'Knockout Rose', R. rugosa (beach rose), Salvia nemorosa (perennial sage), Sedum nuttallianum (yellow stonecrop), Syringa meyeri (Meyer/Korean lilac), Trifolium pratense (red clover), Vicia (vetch), Viola tricolor (wild pansy), Viburnum dentatum (arrowwood viburnum), and Weigela.

Pests/Problems: Juniper Apple Rust horns from galls were seen on Eastern Red Cedar following the recent rains. The invasive Rosa multiflora (Japanese rose) is blooming everywhere.

North Shore (Beverly)

General Conditions: There was a shift in the weather during this reporting period. The dry and hot weather for the previous two weeks was replaced by below average cool temperatures and rainfall. The average daily temperature during this period was 59℉. The highest temperature was 79℉ recorded on June 2 and the minimum temperature was 46℉ recorded on May 28, 29 and 30. A cold front passed through and brought in much needed rains and cool temperatures. Approximately 2.2 inches of rainfall was recorded at Long Hill during this period. The following woody plants were observed in bloom: Kousa dogwood (Cornus kousa), Arrowwood viburnum (Viburnum dentatum), slender deutzia (Deutzia gracilis), white fringetree (Chionanthus virginicus), Chinese fringetree (Chionanthus retusus), American cranberrybush viburnum (Viburnum trilobum), ‘Constellation Rutgers’ dogwood (Cornus x rutgersensis), mock orange (Philadelphus spp.), beautybush (Linnaea amabilis,Kolkwitzia amabilis), flame azalea (Rhododendron calendulaceum), weigela (Weigela florida), black locust (Robinia pseudoacacia) and fragrant snowbell (Styrax obassia). Non-woody plants seen in bloom include: fetterbush (Leucothoe fontanesiana), Scotch rose (Rosa spinosissima), peony (Paeonia spp.), cranesbill (Geranium spp.), bleeding heart (Dicentra spectabilis), Japanese primrose (Primula japonica), columbine (Aquilegia spp.), yellow corydalis (Corydalis lutea), sweet woodruff (Galium odoratum), Solomon’s seal (Polygonatum odoratum) and several annuals.

Pests/Problems: Viburnum leaf beetles were observed causing damage on susceptible viburnums such American cranberry bush viburnum and arrowwood viburnum. The larvae are still small. It is a good time to apply registered insecticides when the larvae are small to control them. Spinosad is a reduced risk insecticide option that may be used to manage viburnum leaf beetle larvae, but it will not be effective against the adult beetles. Note that spinosad is toxic to pollinators until it dries. Research has also shown that insecticidal soap effectively knocks back viburnum leaf beetle larvae. Woolly beech aphids (Phyllaphis fagi) were observed on copper beech clustered in colonies on the undersides of leaves. They remove sap but usually do not affect tree health much. However, they secrete honeydew that can accumulate on lower leaves and branches often resulting in a sooty mold fungus growing on their sugary honeydew waste, discoloring leaves and branches. Rose slug sawfly larvae continue to cause damage on a climbing rose bush. The larvae skeletonize the leaves and in heavy infestations can cause leaves to turn brown and curl. Use horticultural oil, insecticidal soaps, or spinosad, targeting the spray on undersides of the leaves. Bacillus thuringiensis (Bt) will not control rose slug sawfly larvae. Mosquitoes and ticks are still very active. Protect yourself with a repellent when working outdoors.

East Region (Boston)

General Conditions: In mid-May we had a 15 day stretch with no precipitation. May ended with six consecutive days of rain totaling 3 inches bringing the total for May to 4.65 inches. Soils are adequately moist. We experienced some near record low daytime high temperatures reaching 49˚F on the 29th and 30th. Calycanthus floridus (Carolina allspice), Linnaea amabilis/Kolkwitzia amabilis (beautybush) and Philadelphus spp. (mock orange) are flowering.

Pests/Problems: Aphids continue to be prevalent throughout the landscape. Cottony camellia scale (Pulvinaria floccifera) has been observed on ornamental hollies. Rose slug sawfly larvae (Endelomyia aethiops) can be found skeletonizing rose foliage. Multiflora rose (Rosa multiflora) and black swallowwort (Cynanchum louiseae) are in flower; garlic mustard (Alliaria petiolata) has gone to seed.

Metro West (Acton)

General Conditions: The summer-like temperatures continued into this reporting period, but then later in the week, especially over the holiday weekend, the weather turned wet and cool, more typical of April weather. A high temperature of 91°F was recorded on the 26^th and a low of 45°F recorded on the 29^th but the 3.05” of precipitation recorded on 6 days during this reporting period is the talk of the town! The average monthly rainfall for May is 4.04” and 5.51” was recorded for this area. For the month of June, the average monthly rainfall is 3.93”. Observed in some stage of bloom this past week were the following woody plants: Aesculus × carnea 'Briotii' (red horse chestnut), Calycanthus floridus (Carolina allspice), Chionanthus retusus (Chinese fringe tree), C. virginicus (fringe tree), Cladrastis lutea (yellowwood), Cornus x rutgersensis 'Ruth Ellen' (Rutgers hybrid dogwood), Cornus sericea (redosier dogwood), Cotinus coggygria (common smokebush), Deutzia gracilis ‘Nikko’ (dwarf slender deutzia), Kolkwitzia amabilis/Linnaea amabilis (beautybush), Leucothoe axillaris (coast leucothoe), Lonicera maackii (Amur honeysuckle), Philadelphus spp. (mock orange), Physocarpus opulifolius (common ninebark), Rhododendron spp. (rhododendron and azalea), Robinia pseudoacacia (black locust), Rosa spp. (rose), R. rugosa (beach rose), R. 'Knockout' (knockout family of roses), Rubus spp. (blackberry, bramble, raspberry), Spiraea spp. (bridal wreath), Syringa spp. (late blooming lilac), Viburnum plicatum var. tomentosum (doublefile viburnum), V. sargentii (sargent viburnum), and Weigela florida (old fashioned weigela).

Woody vines observed in bloom include Clematis spp. (clematis), Lonicera sempervirens (trumpet honeysuckle) and Wisteria spp. (wisteria). Contributing even more color and interest to the landscape are some flowering herbaceous plants including: Ajuga reptans (bugleweed), Alchemilla mollis (lady’s mantle), Allium spp. [ornamental flowering onion, including A. giganteum (giant onion), and A. schoenoprasum (chives)], Amsonia hubrichtii (Arkansas blue star), Aquilegia spp. (columbine cultivars), Baptisia australis (blue false indigo), Cerastium tomentosum (snow in summer), Chrysogonum virginianum (green and gold), Dianthus deltoides (maiden pink), Dicentra eximia (fringed bleeding heart), D. spectabilis (old fashioned bleeding heart), D. spectabilis ‘Alba’ (white old fashioned bleeding heart), Dictamnus albus (gas plant), Dodecatheon meadia (shooting star), Galium odoratum (sweet woodruff), Geranium maculatum (wild geranium), G. macrorrhizum (bigroot geranium), G. sanguineum (cranesbill geranium), Hemerocallis spp. (early flowering daylily), Iris germanica (bearded iris), I. sibirica (Siberian iris), Lupinus 'Russell Woodfield Hybrids' (lupine), Maianthemum dilatatum (false lily of the valley), Nepeta spp. (ornamental catmint), Paeonia spp. (peony), Papaver orientale (oriental poppy), Phlox divaricata (Canadian phlox), P. stolonifera (creeping phlox), Primula spp. (primrose), Saponaria ocymoides (rock soapwort), Thymus praecox (thyme), Tradescantia sp. (spiderwort), Veronica umbrosa ‘Georgia Blue’ (speedwell), Vinca minor (periwinkle), and Zizia aptera (heart-leaved golden Alexanders).

Pests/Problems: Many of our most invasive weeds have flowered and are beginning to set seed. Those include: Alliaria petiolata (garlic mustard), Berberis thunbergii (barberry), Elaeagnus umbellata (autumn-olive), Euonymous alatus (burning bush) and Rhamnus cathartica (common buckthorn). Lonicera maackii (Amur honeysuckle), a woody shrub, continues to bloom as well as Rosa multiflora (multiflora rose), a woody, thorny, vining shrub with noticeable white flowers now in full bloom. I also observed Woolly Beech Aphid (Phyllaphis fagi) on the underside of Fagus sylvatica (European beech) leaves and powdery mildew on Filipendula sp. (queen of the prairie).

Central Region (Boylston)

General Conditions: Wow! A month’s precipitation over the course of a few days to end the month has left the garden feeling lush and given the gardener a brief respite from fighting off parched soils with constant irrigation. Memorial Day weekend was a total washout, but the deep soaking was exactly what we needed here in the Central Region. As soon as the rain stopped falling, the abundant pollen coated all surfaces in a sheen of yellow-green once again. There is plenty in bloom in the garden as well. One particular underused tree is just coming into full bloom, Cladrastis kentukea (yellow wood). Although not native to New England, yellow wood is native to the mid-Atlantic region. A far less aggressive species than black locust (Robinia pseudoacacia), it’s another member of the legume family that blooms in late spring. Yellow wood features beautiful white flowers with a light fragrance and blue-green foliage turning yellow in the fall. A handsome tree that tends to bloom heavily every other year, Cladrastis kentukea appears to be having a good floral display this season.

Pests/Problems: Thanks to the plentiful rainfall to end the month of May, drought stress is no longer a concern, at least for the moment. Next week’s forecast looks hot and dry, so we may be right back to drought concern by the next reporting period. Garden weeds have exploded in the past two weeks. Young gypsy moth caterpillars were observed feeding on recently planted apple trees.

Pioneer Valley Region (Amherst)

General Conditions: Summer has arrived in the Pioneer Valley after a cold and soggy Memorial Day weekend. May of 2021 started with several days of soaking rain and it ended just the same. In between, high temperatures were 15–20°F above normal (5/18–5/23) and there was a 16-day stretch with no precipitation (5/10–5/26). Conditions on the final day of the “May drought” were hot and humid, as temperatures hovered at or over 90°F across the valley. A large band of strong and fast-moving thunderstorms then swept through the region and temperatures bottomed out over the next several days. Highs on 5/29 and 5/30 only managed to reach the upper 40s; a staggering turn of events from just a few days earlier. The cool temperatures were the result of two long-duration storms on 5/28–29 and 5/30–31 that soaked southern New England. All told, there were five days with measurable rainfall over a six-day period (5/26–5/31) with 2.66” recorded at the Easthampton gauge. It was the soaking rain that we needed, although one respectable day over the holiday weekend would have been nice. Soils are now moist and supplemental watering for many plants can be scaled back or suspended… for now. The rain and temperatures in the 40s decreased both sun and shade soil temperatures from last week’s readings. The cool temperatures were also a reprieve for tender shoots and stems as new growth continues. The rain helped to wash away the pollen that coated every possible outdoor surface. Pollen levels have been high this year, a trend that will likely continue for a few more weeks. The long-term forecast calls for scattered showers and then sun and high temperatures in the upper 80s to 90s.

Pests/Problems: Symptoms of needle blight are very conspicuous now on eastern white pines, in both forest and landscape settings. Diseased trees have thin canopies and are shedding large volumes of older needles. With new needles approximately 1/8–1/4 elongated, at the time of writing, affected trees can look devoid of any foliage from a distance. White pine needle damage is a chronic condition that can be caused by multiple native fungal pathogens, which primarily include: Lecanosticta, Septorioides, Bifusella and Lophophacidium. In some cases, multiple needle blight pathogens can be found on individual trees. Leaf browning and curling on crabapple, due to apple scab, is now visible. While older, interior canopy leaves may begin shedding, apple and crabapple will continue to develop new shoots and foliage during the month of June. The orange-colored lesions caused by cedar-apple rust are now visible on apples. Espalier apple cultivars seem especially susceptible to this disease and trees on the UMass campus have numerous leaf spots already. Beech anthracnose was recently observed on the UMass campus, pictured below. To date, beech leaf disease has not been observed on European and American beech in Hampshire County. Bagworms (Thyridopteryx ephemeraeformis) are increasingly becoming an important insect pest in the valley and several overwintering bags were found in the canopies of eastern red cedar and nearby white pine, pictured below. Sycamores continue to slowly leaf out, due to repeated infection of new foliage and shoots by the anthracnose pathogen Apiognomonia veneta. Leafless canopies are common in early June so it’s still too early to determine if this is a bad year for the disease. Phyllosticta leaf blotch of witch hazel is abundant on certain plants right now. The disease first appears as dark purple to brown-colored, circular spots but these can coalesce to create large, necrotic blotches that may consume entire leaves. Interior canopy leaves are often most diseased, due to higher levels of shade. Some other common and mostly unimportant foliar diseases are becoming visible now too, such as purple eye leaf spot of maple. Symptoms of the iris borer (Macronoctua onusta) were observed on bearded iris (Iris x germanica). These included chewing holes where the caterpillars entered the leaf, a clear exudate streaming from the wounds, brown streaking on the foliage, and a lack of flowers. The leaves were cut to the base and then dissected to locate the caterpillars for confirmation. One section of the plant was dug to examine the rhizome for damage. Mature caterpillars bore into the rhizome by mid-season (~July) to feed and overwinter, but no damage was located. Continue to scout for and prune dead stems on deciduous hardwoods, especially on trees with thin bark (dogwood, Japanese maple, etc.) that can be prone to cankering outbreaks. Spruce spider mite injury is now becoming very apparent on infested trees. Scout for flecking symptoms and webbing on interior canopy needles and treat accordingly. Bladder gall mites are now abundant on the foliage of elm, maple, hackberry, among other deciduous hardwoods. Balsam twig aphid damage can be found on true firs (Abies) in the landscape. The current season’s shoots will have distorted and curled needles. This early season pest causes only minor injury and often does not warrant treatment. Mosquito populations continue to be very high right now in the valley and the rain will only fuel their continued persistence. Weeding season is now in full swing.

Berkshire Region (Great Barrington)

General Conditions: The past week saw a sudden transition from cold, damp weather - akin to early March - to warm and sometimes hot weather. Just how cold it was is exemplified by a report in the Berkshire Eagle which stated that “Saturday’s (May 29) high temperature of only 46˚F at Pittsfield Municipal Airport smashed the previous coolest high for the date, 53˚F, which was set in 1936, according to the National Weather Service’s database.” Daily highs now are in the 70s and 80s with 90˚F possible in some locales. Accompanying the transition to hot weather is the potential for frequent showers. As a result, soil moisture levels are high but not saturated except for sites with heavy clay soils. Landscapes, natural and managed, remain very colorful with a wide range of herbaceous and woody plants in bloom. Related to the abundance of bloom is the high amount of tree pollen, a misery to those who suffer from pollen allergies.

Pests/Problems: Plant pests most frequently observed over the past week were: viburnum leaf beetle (larval stage), imported willow leaf beetle (larval stage), boxwood leaf miner (adult stage), forest tent caterpillar (larval stage), hydrangea leaf tier (larvae), boxwood pysllids, aphids on a variety of herbaceous and woody plants, wooly beech aphid, and allium leaf miner and allium thrips on ornamental alliums. Borers were found in twigs of black lace elderberry (Sambucus nigra). Despite the moisture, plant disease pressures are seemingly low this spring. A few exceptions are Volutella blight of pachysandra (on old plant foliage only), apple scab, and cedar apple rust. Warm temperatures and moist weather are increasing the population of mosquitoes. Black flies, gnats, wasps, and ants are abundant. Worst of all continues to be a very profuse population of black-legged ticks. The damp weather has also increased the occurrence of slugs. Animal damage to plants remains high, especially from voles who tunnel through the soil beneath landscape plantings. Poison ivy is rampant right now and is frequently found invading ground covers in managed landscapes.

Regional Scouting Credits

• CAPE COD REGION - Russell Norton, Horticulture and Agriculture Educator with Cape Cod Cooperative Extension, reporting from Barnstable.
• SOUTHEAST REGION - Brian McMahon, Arborist, reporting from the Dighton area.
• NORTH SHORE REGION - Geoffrey Njue, Green Industry Specialist, UMass Extension, reporting from the Long Hill Reservation, Beverly.
• EAST REGION - Kit Ganshaw & Sue Pfeiffer, Horticulturists reporting from the Boston area.
• METRO WEST REGION – Julie Coop, Forester, Massachusetts Department of Conservation & Recreation, reporting from Acton.
• CENTRAL REGION - Mark Richardson, Director of Horticulture reporting from Tower Hill Botanic Garden, Boylston.
• PIONEER VALLEY REGION - Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, reporting from Amherst.
• BERKSHIRE REGION - Ron Kujawski, Horticultural Consultant, reporting from Great Barrington.

Woody Ornamentals

Diseases

Recent pests and pathogens of interest seen in the UMass Extension Plant Diagnostic Lab https://ag.umass.edu/services/plant-diagnostics-laboratory:

• There have been several reports of intensifying beech leaf disease (BLD) outbreaks in Middlesex, Plymouth and Bristol Counties on both American (Fagus grandifolia) and European beech (F. sylvatica). Locations in Connecticut, Rhode Island and Massachusetts with isolated cases of the disease have seen a surge of new BLD cases in 2021. Symptoms of the disease include dark interveinal banding and puckering/cupping that appear convex on the upper leaf surface. Marginal distortion and curling may also occur. Research and field observations have shown that infected leaves emerge from the buds with symptoms of the disease, indicating they are injured prior to bud break. The nematode responsible for BLD (Litylenchus crenatae ssp. mccannii) is infecting the buds and symptomatic leaves appear at bud break. Trials are underway testing the utility of emamectin benzoate injections. While this chemical is toxic to nematodes, it’s not clear if the chemical is properly translocating to the canopy after injection. Additional trials are testing phosphites as soil drench and injection. For American beech, there is the added stress of beech bark disease, a chronic cankering disease that is also capable of killing trees.

For more information on beech leaf disease, see this recent USDA Forest Service Pest Alert:

https://usfs-public.app.box.com/v/CurrentPestAlerts/file/787426913431

For more information on other common disease and insect issues of beech that could be mistaken for BLD, see here: https://www.dec.ny.gov/lands/120589.html

• Stem and branch cankering in the canopy of a bur oak (Quercus macrocarpa) caused by Botryosphaeria. Tree is approximately 60-years-old and resides in a residential lawn setting with a mixture of sun and shade. In spring of 2020, the tree exhibited shoot tip dieback throughout the canopy which has intensified this season. Submitted stems were desiccated with brown-colored vascular tissue. In addition, there were numerous black-colored fruiting bodies rupturing through the stem bark. Oaks suffering from landscape stresses (i.e. compacted soils, drought stress, limited rooting zone, competition with turfgrasses, etc.) are more susceptible to stem cankering infections from Botryosphaeria.
• Squirrel damage in the canopy of a mature elm (Ulmus sp.). The tree is approximately 20-years-old and resides in a residential lawn setting. In mid-May, numerous shoot tips, approximately 6–8” long, were found on the ground under the canopy. The base of the cut stems exhibited chewing marks. During the summer months, squirrels will clip the shoot tips on elm, oak and other deciduous hardwoods to build nests and also to drink sap during extended dry periods. The dry and warm conditions in mid-May could have forced squirrels to seek out tree sap if no water sources were available.
• Shoot tip browning and branch dieback on arborvitae (Thuja occidentalis) due to arborvitae needle blight. Two fungal pathogens are most often responsible for needle blight on arborvitae: Pestalotiopsis and Phyllosticta. On one sample, young emerald green arborvitae (T. occidentalis ‘Smargd’) that were planted in 2020 exhibited serious decline this season. The trees were planted too deep and reside in soils composed of both sand and clay. It’s not clear if any supplemental water was provided after transplanting. Submitted shoots were pale green to brown and desiccated. Another sample came from trees that are 12-years-old and have been present at the site for five years. They were planted as a screen in a shaded setting at the rear edge of a property adjacent to a slope. They are provided with drip irrigation and the soils are described as loam-based with good drainage. This spring, shoot tip dieback developed and the symptoms appear to be intensifying. There was no sign of insect infestation from the spruce spider mite or arborvitae leafminer.

Report by Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, UMass Amherst.

Insects

Upcoming Educational Programs:

Looking for more information about important arthropod vectors of human pathogens in Massachusetts? Don’t miss UMass Extension’s Tick and Mosquito Education Days!

June 8 & June 15 from 10:00 AM – 12:10 PM

This 2-day virtual webinar series will call upon topic experts to provide information about the seasonality, biology, and the diseases these organisms vector, as well as how to manage these pests and steps you can take to protect yourself.

June 8 – Tick Topics:

10:00 – 11:00 AM: Tick Management in the Landscape, Larry Dapsis, Cape Cod Cooperative Extension

11:10 AM – 12:10 PM: The Outreach Hiker’s Guide to Tick-ology: Personal tick bite prevention and more! Blake Dinius, Plymouth County Extension

June 15 – Mosquito Topics:

10:00 - 11:00 AM: Mosquitoes in Massachusetts, Arboviruses and Protecting Yourself, Dr. Jennifer Forman Orth, MA Dept. of Agricultural Resources

11:10 AM – 12:10 PM: Dealing With the Asian Tiger Mosquito: Incorporating an Invasive Species into an Existing Mosquito Control Program, Priscilla Matton, Superintendent, Bristol County Mosquito Control Project

For more information and to register, visit: https://ag.umass.edu/landscape/events/tick-mosquito-education-days

Really Cool Beneficial Insects in the Garden:

• Antlions: These really cool insects are members of the Order Neuroptera (antlions, lacewings, mantispids, and owlflies) and in the Family Myrmeleontidae (antlions and owlflies). In general, the Neuroptera are medium-sized insects with four, many-veined wings as adults. They have complete metamorphosis, with egg, larva, pupa, and adult stages. Antlion larvae are sometimes referred to as “doodlebugs”, due to their pitfall-trap digging behavior. These voracious predators create their own pitfall traps in sandy soils, and lie-in-wait (hidden in the sand at the bottom of the pit) for ants and other suitable prey to fall in. Antlion larvae frequently make their funnel-shaped pits at the base of foundations in fine, dry soils. They may also be found under eaves or porches (areas that are protected from direct rainfall). While soil type may differ, it appears that they do require dry soils with fine texture. (If you are looking to attract antlions to your foundation planting, entomologists have suggested this may be done by pouring a thin layer of fine textured sand next to the foundation, beneath the eaves.) The larvae are peculiar in their appearance, with broad, flattened bodies, short legs used for crawling backward, and a flattened head with impressive sickle-shaped mandibles (mouthparts). Larvae look very different from the adult antlions, which are similar to a damselfly in appearance. Antlion larvae do not cause damage to plants, and should be preserved in gardens and landscapes. They are also fascinating insects to teach children about – adults and kids alike will enjoy watching an antlion attack and flick sand at a thin, stiff blade of grass used to prod the bottom of their pit. These insects blend in so well with the soil, do not be surprised if you only suddenly notice their large mandibles when they move!

Insects and Other Arthropods of Medical Importance:

• American Dog Tick: Anecdotally, Dermacentor variabilis adults are prevalent in certain locations of Massachusetts at this time. Reports from Cape Cod of adult dog ticks crawling on the siding of homes have been noted. Photographic evidence of adult dog ticks crawling up metal objects leaning against a home located in a heavily wooded area of Berkshire County, MA have also been reported recently (5/9/2021). The images shown here are adult stage dog ticks removed from a dog following a roadside walk in Hampshire County on both 5/6/21 (4 ticks removed) and 5/7/21 (3 ticks removed).

The American dog tick is found throughout most of North America. It may be encountered in forest edges, fields, along walkways and roadways, sidewalks, and trails. Adult stage ticks may be found on raccoons, skunks, cats, dogs, and other medium-sized hosts. Larvae and nymphs can be found on mice, voles, rats, and chipmunks. Adult males and females are active between April and early-August. Both adult males and females will feed, including on people. Nymphs and larvae of this species rarely attach to people or their pets. This species of tick can transmit lesser-known diseases such as Rocky Mountain Spotted Fever (not frequently infecting humans, according to CDC reports) and Tularemia (rarely infecting humans, according to CDC reports). For more information about the American dog tick, visit: https://web.uri.edu/tickencounter/species/dog-tick/ .

• Deer Tick/Blacklegged Tick: Check out the archived FREE TickTalk with TickReport webinars available here: https://ag.umass.edu/landscape/education-events/webinars .

*Ixodes scapularis - We are now entering the time of year when deer tick larvae and nymphs are frequently encountered. Larvae may be encountered in April, but in some locations may peak in their activity in August, while still being encountered through November. Nymphs are encountered from April through July, peaking in June. Nymphs are again present in October and November. For images of all deer tick life stages, along with an outline of the diseases they carry, and their timing of activity, visit: http://www.tickencounter.org/tick_identification/deer_tick .

Anyone working in the yard and garden should be aware that there is the potential to encounter deer ticks. The deer tick or blacklegged tick can transmit Lyme disease, human babesiosis, human anaplasmosis, and other diseases. Preventative activities, such as daily tick checks, wearing appropriate clothing, and permethrin treatments for clothing (according to label instructions) can aid in reducing the risk that a tick will become attached to your body. If a tick cannot attach and feed, it will not transmit disease. For more information about personal protective measures, visit: http://www.tickencounter.org/prevention/protect_yourself .

The Center for Agriculture, Food, and the Environment provides a list of potential tick identification and testing resources here: https://ag.umass.edu/resources/tick-testing-resources

*Note that deer ticks (Ixodes scapularis) are not the only disease-causing tick species found in Massachusetts. The American dog tick (Dermacentor variabilis) and the lone star tick (Amblyomma americanum) are also found throughout MA. Each can carry their own complement of diseases, including others not mentioned above. Anyone working or playing in tick habitats (wood-line areas, forested areas, and landscaped areas with ground cover) should check themselves regularly for ticks while practicing preventative measures.

• Mosquitoes: According to the Massachusetts Bureau of Infectious Disease and Laboratory Science and the Department of Public Health, there are at least 51 different species of mosquito found in Massachusetts. Mosquitoes belong to the Order Diptera (true flies) and the Family Culicidae (mosquitoes). As such, they undergo complete metamorphosis, and possess four major life stages: egg, larva, pupa, and adult. Adult mosquitoes are the only stage that flies and many female mosquitoes only live for 2 weeks (although the life cycle and timing will depend upon the species). Only female mosquitoes bite to take a blood meal, and this is so they can make eggs. Mosquitoes need water to lay their eggs in, so they are often found in wet or damp locations and around plants. Different species prefer different habitats. It is possible to be bitten by a mosquito at any time of the day, and again timing depends upon the species. Many are particularly active from just before dusk, through the night, and until dawn. Mosquito bites are not only itchy and annoying, but they can be associated with greater health risks. Certain mosquitoes vector pathogens that cause diseases such as West Nile virus (WNV) and eastern equine encephalitis (EEE).

For more information about mosquitoes in Massachusetts, visit: https://www.mass.gov/service-details/mosquitoes-in-massachusetts

There are ways to protect yourself against mosquitoes, including wearing long-sleeved shirts and long pants, keeping mosquitoes outside by using tight-fitting window and door screens, and using insect repellents as directed. Products containing the active ingredients DEET, permethrin, IR3535, picaridin, and oil of lemon eucalyptus provide protection against mosquitoes.

For more information about mosquito repellents, visit: https://www.mass.gov/service-details/mosquito-repellents and https://www.cdc.gov/mosquitoes/mosquito-bites/prevent-mosquito-bites.html .

• Wasps/Hornets: Many wasps are predators of other arthropods, including pest insects such as certain caterpillars that feed on trees and shrubs. Adult wasps hunt prey and bring it back to their nest where young are being reared, as food for the immature wasps. A common such example are the paper wasps (Polistes spp.) who rear their young on chewed up insects. They may be seen searching plants for caterpillars and other soft-bodied larvae to feed their young. Paper wasps can sting, and will defend their nests, which are open-celled paper nests that are not covered with a papery “envelope”. These open-celled nests may be seen hanging from eaves or other outdoor building structures. Aerial yellow jackets and hornets create large aerial nests that are covered with a papery shell or “envelope”. Common yellow jacket species include those in the genus Vespula. Dolichovespula maculata is commonly known as the baldfaced hornet, although it is not a true hornet. The European hornet (Vespa crabro) is three times the size of a yellow jacket and may be confused for the Asian giant hornet (Vespa mandarinia). The European hornet is known to Massachusetts, but the Asian giant hornet is not. If you are concerned that you have found or photographed an Asian giant hornet, please report it here: https://massnrc.org/pests/report.aspx . Paper wasps and aerial yellowjackets overwinter as fertilized females (queens) and a single female produces a new nest annually in the late spring. Nests are abandoned at the end of the season. Queens start new nests, lay eggs, and rear new wasps to assist in colony/nest development.Some people are allergic to stinging insects, so care should be taken around wasp/hornet nests. Unlike the European honeybee (Apis mellifera), wasps and hornets do not have barbed stingers, and therefore can sting repeatedly when defending their nests. It is best to avoid their nests, and if that cannot be done and assistance is needed to remove them, consult a professional.

Woody ornamental insect and non-insect arthropod pests to consider, a selected few:

Invasive Insects & Other Organisms Update:

• Spotted Lanternfly: (Lycorma delicatula, SLF) is not known to be established in Massachusetts landscapes at this time. However, due to the great ability of this insect to hitchhike using human-aided movement, it is important that we remain vigilant in Massachusetts and report any suspicious findings. Spotted lanternfly reports can be sent here: https://massnrc.org/pests/slfreport.aspx .

The Massachusetts Department of Agricultural Resources has recently released spotted lanternfly Best Management Practices for Nurseries and Landscapers: https://massnrc.org/pests/linkeddocuments/MANurseryBMPs.pdf

And Best Management Practices for Moving Companies and the Moving Industry: https://massnrc.org/pests/linkeddocuments/SLFChecklistMovingIndustryMA.pdf

Now is a great time to provide copies of these BMP’s to employees, customers, family, and friends! The more eyes we have out there looking for spotted lanternfly, the better. Use the above BMP’s as a guide to help you inspect certain items coming from CT, DE, MD, NC, NJ, NY, OH, PA, WV, and VA.

UMass Extension is teaming up with UMass Amherst’s Department of Environmental Conservation, the USDA APHIS, and the Massachusetts Department of Agricultural Resources to monitor for the spotted lanternfly in Massachusetts. A team including members of UMass Extension’s Landscape, Nursery, and Urban Forestry Program, Extension’s Fruit Program, Stockbridge School of Agriculture, and the Department of Environmental Conservation at UMass, Amherst are undertaking a nine-month integrated research and extension project to develop effective tools to detect the spotted lanternfly.

The researchers associated with this project (Dr. Joseph Elkinton, Dr. Jeremy Andersen and Dr. Jaime Pinero) will be working with Dr. Miriam Cooperband of the USDA APHIS lab on Cape Cod to identify and evaluate airborne attractants that can improve the ability to detect SLF in traps. Dr. Cooperband has identified several attractant lures released from host plants of SLF. She is currently working on pheromones produced by SLF that may be much more attractive. The UMass team will help her conduct field tests of these new lures, while also assisting the Massachusetts Department of Agricultural Resources (MDAR) in monitoring for SLF in Massachusetts. UMass Extension Entomologist, Tawny Simisky, will periodically report on progress made during the course of this project. For more information, please visit: https://ag.umass.edu/cafe/news/looking-for-spotted-lanternfly-recent-invasive-arrival

This insect is a member of the Order Hemiptera (true bugs, cicadas, hoppers, aphids, and others) and the Family Fulgoridae, also known as planthoppers. The spotted lanternfly is a non-native species first detected in the United States in Berks County, Pennsylvania and confirmed on September 22, 2014.

For a map of known, established populations of SLF as well as detections outside of these areas where individual finds of spotted lanternfly have occurred (but no infestations are present), visit: https://nysipm.cornell.edu/environment/invasive-species-exotic-pests/spotted-lanternfly/

The spotted lanternfly is considered native to China, India, and Vietnam. It has been introduced as a non-native insect to South Korea and Japan, prior to its detection in the United States. In South Korea, it is considered invasive and a pest of grapes and peaches. The spotted lanternfly has been reported feeding on over 103 species of plants, according to new research (Barringer and Ciafré, 2020) and when including not only plants on which the insect feeds, but those that it will lay egg masses on, this number rises to 172. This includes, but is not limited to, the following: tree of heaven (Ailanthus altissima) (preferred host), apple (Malus spp.), plum, cherry, peach, apricot (Prunus spp.), grape (Vitis spp.), pine (Pinus spp.), pignut hickory (Carya glabra), sassafras (Sassafras albidum), serviceberry (Amelanchier spp.), slippery elm (Ulmus rubra), tulip poplar (Liriodendron tulipifera), white ash (Fraxinus americana), willow (Salix spp.), American beech (Fagus grandifolia), American linden (Tilia americana), American sycamore (Platanus occidentalis), big-toothed aspen (Populus grandidentata), black birch (Betula lenta), black cherry (Prunus serotina), black gum (Nyssa sylvatica), black walnut (Juglans nigra), dogwood (Cornus spp.), Japanese snowbell (Styrax japonicus), maple (Acer spp.), oak (Quercus spp.), and paper birch (Betula papyrifera).

The adults and immatures of this species damage host plants by feeding on sap from stems, leaves, and the trunks of trees. In the springtime in Pennsylvania (late April - mid-May) nymphs (immatures) are found on smaller plants and vines and new growth of trees and shrubs. Third and fourth instar nymphs migrate to the tree of heaven and are observed feeding on trunks and branches. Trees may be found with sap weeping from the wounds caused by the insect’s feeding. The sugary secretions (excrement) created by this insect may coat the host plant, later leading to the growth of sooty mold. Insects such as wasps, hornets, bees, and ants may also be attracted to the sugary waste created by the lanternflies, or sap weeping from open wounds in the host plant. Host plants have been described as giving off a fermented odor when this insect is present.

Adults are present by the middle of July in Pennsylvania and begin laying eggs by late September and continue laying eggs through late November and even early December in that state. Adults may be found on the trunks of trees such as the tree of heaven or other host plants growing in close proximity to them. Egg masses of this insect are gray in color and look similar in some ways to gypsy moth egg masses.

Host plants, bricks, stone, lawn furniture, recreational vehicles, and other smooth surfaces can be inspected for egg masses. Egg masses laid on outdoor residential items such as those listed above may pose the greatest threat for spreading this insect via human aided movement.

For more information about the spotted lanternfly, visit this fact sheet: https://ag.umass.edu/landscape/fact-sheets/spotted-lanternfly .

• Emerald Ash Borer: (Agrilus planipennis, EAB) Since the New Year, the Massachusetts Department of Conservation and Recreation has confirmed at least 22 new community detections of emerald ash borer in Massachusetts. To date, 11 out of the 14 counties in Massachusetts have confirmed emerald ash borer. (The remaining counties where EAB has yet to be detected are Barnstable, Dukes, and Nantucket counties.)A map of these locations and others previously known across the state may be found here: https://ag.umass.edu/fact-sheets/emerald-ash-borer .

This wood-boring beetle readily attacks ash (Fraxinus spp.) including white, green, and black ash and has also been found developing in white fringe tree (Chionanthus virginicus) and has been reported in cultivated olive (Olea europaea). Adult insects of this species will not be present at this time of year. Signs of an EAB infested tree may include (at this time) D-shaped exit holes in the bark (from adult emergence in previous years), “blonding” or lighter coloration of the ash bark from woodpecker feeding (chipping away of the bark as they search for larvae beneath), and serpentine galleries visible through splits in the bark, from larval feeding beneath. It is interesting to note that woodpeckers are capable of eating 30-95% of the emerald ash borer larvae found in a single tree (Murphy et al. 2018). Unfortunately, despite high predation rates, EAB populations continue to grow.

For further information about this insect, please visit: https://ag.umass.edu/fact-sheets/emerald-ash-borer . If you believe you have located EAB-infested ash trees, particularly in an area of Massachusetts not identified on the map provided, please report here: https://massnrc.org/pests/eabreport.htm .

• Gypsy Moth:(Lymantria dispar) thanks to the gypsy moth caterpillar killing fungus, Entomophaga maimaiga, the recent outbreak of gypsy moth in Massachusetts has come to an end! Most locations in Massachusetts will not see damaging or even noticeable populations of this insect in 2021. However, there have been recent reports of young gypsy moth caterpillars feeding on susceptible hosts. While this may be the case in certain locations, we do not expect widespread defoliation from this insect in 2021. Gypsy moth has been in Massachusetts since the 1860's. This invasive insect from Europe often goes unnoticed, thanks to population regulation provided by the entomopathogenic fungus, E. maimaiga, as well as a NPV virus specific to gypsy moth caterpillars. (And to a lesser extent many other organisms, including other insects, small mammals, and birds who feed on gypsy moth.) However, if environmental conditions do not favor the life cycle of the fungus, outbreaks of gypsy moth caterpillars are possible. (Such as most recently from 2015-2018, with a peak in the gypsy moth population in 2017 in Massachusetts.)

Check out Episode 1 of InsectXaminer to reminisce about the 2015-2018 outbreak of this insect: https://ag.umass.edu/landscape/education-events/insectxaminer

• Asian Longhorned Beetle: (Anoplophora glabripennis, ALB) Look for signs of an ALB infestation which include perfectly round exit holes (about the size of a dime), shallow oval or round scars in the bark where a female has chewed an egg site, or sawdust-like frass (excrement) on the ground nearby host trees or caught in between branches. Be advised that other, native insects may create perfectly round exit holes or sawdust-like frass, which can be confused with signs of ALB activity.

The regulated area for Asian longhorned beetle is 110 miles² encompassing Worcester, Shrewsbury, Boylston, West Boylston, and parts of Holden and Auburn. If you believe you have seen damage caused by this insect, such as exit holes or egg sites, on susceptible host trees like maple, please call the Asian Longhorned Beetle Eradication Program office in Worcester, MA at 508-852-8090 or toll free at 1-866-702-9938.

To report an Asian longhorned beetle find online or compare it to common insect look-alikes, visit: http://massnrc.org/pests/albreport.aspx or https://www.aphis.usda.gov/pests-diseases/alb/report .

• White Spotted Pine Sawyer (WSPS): Monochamus scutellatus adults can emerge in late May throughout July, depending on local temperatures. This is a native insect in Massachusetts and is usually not a pest. Larvae develop in weakened or recently dead conifers, particularly eastern white pine (Pinus strobus). However, the white spotted pine sawyer looks very similar to the invasive Asian Longhorned Beetle, Anoplophora glabripennis, ALB. ALB adults do not emerge in Massachusetts until July and August. Beginning in July, look for the key difference between WSPS and ALB adults, which is a white spot in the top center of the wing covers (the scutellum) on the back of the beetle. White spotted pine sawyer will have this white spot, whereas Asian longhorned beetle will not. Both insects can have other white spots on the rest of their wing covers; however, the difference in the color of the scutellum is a key characteristic. See the Asian longhorned beetle entry above for more information about that non-native insect.
• Jumping Worms: In recent years, public concern about Amynthas spp. earthworms, collectively referred to as “jumping or crazy or snake” worms, has dramatically increased. University researchers and Extension groups in many locations in the US are finding that these species cause not only forest ecosystem disturbances, but may also negatively impact soil structure and reduce plant growth in gardens and managed landscapes. They do this by voraciously devouring the organic layer of the soil while feeding very close to the soil surface, unlike other species of earthworms. In woodland areas, they can quickly eat all of the leaf litter on the forest floor. Jumping worms also leave a distinct grainy soil full of worm castings. The soil becomes granular and may look like dried coffee grounds.

Unfortunately, there are currently no research-based management options available for these earthworms. So prevention is essential – preventing their introduction and spread into new areas is the best defense against them. Adult jumping worms can be 1.5 – 8 inches or more in length. Their clitellum (collar-like ring) is roughly located 1/3 down the length of the worm (from the head) and is smooth and cloudy-white and constricted. These worms may also wiggle or jump when disturbed, and can move across the ground in an S-shape like a snake. While the exact timing of their life cycle in MA might not be completely understood, their life cycle may be expected to go (roughly) something like this: they hatch in the late spring in 1-4 inches of soil, mature into adults during the summer and adults lay eggs sometime in August, and it is thought that their cocoons overwinter. (Adults perish with frost.) It is also worth noting here that jumping worms do not directly harm humans or pets.

For more information, listen to Dr. Olga Kostromytska’s presentation here: https://ag.umass.edu/landscape/education-events/invasive-insect-webinars

Suggested reading includes Dr. Kostromytska’s recent “Hot Topics” article in Hort Notes (including an identification guide), here: https://ag.umass.edu/landscape/newsletters/hort-notes/hort-notes-2021-vol-323

Additional resources can also be found here:

University of Minnesota Extension: https://extension.umn.edu/identify-invasive-species/jumping-worms

Cornell Cooperative Extension: http://ulster.cce.cornell.edu/environment/invasive-pests/jumping-worm

UNH Extension: https://extension.unh.edu/blog/invasive-spotlight-jumping-worms

Tree & Shrub Insects & Mites:

• Adelgids of Larch: There are at least two species of adelgid that feed alternatively on larch and spruce. Both have a late spring generation on larch. In this particular case, a species of adelgid was observed on Japanese larch (Larix kaempferi) on 6/1/2021 in Amherst, MA. Two species that occur on larch in New England are both in the genus Adelges. A. lariciatus and A. laricis. Of the two, A. laricis has been recorded on Japanese larch, so the assumption is that is the species we have here. However, conservatively, an identification to genus in this case is likely more appropriate. The late spring generation of these adelgids on larch can be impressive. The population may be so high, the tree may appear as if dusted with snow. In the case of this observation, females with a white, powdery wax covering their otherwise dark, nearly black bodies can be seen beneath a dissecting microscope, surrounded by clusters of eggs. The nymphs (immatures), to the naked eye, look like tiny black specks found on the needles.
• Arborvitae Leafminer: In New England and eastern Canada, four species of leafminers are known to infest arborvitae. These include Argyresthia thuiella, A. freyella, A. aureoargentella, and Coleotechnites thujaella. The arborvitae leafminer, A. thuiella, is the most abundant of these and has the greatest known range when compared to the others. (It is also found in the Mid-Atlantic States and as far west as Missouri). Moths of this species appear from mid-June to mid-July and lay their eggs. The damage caused by all of these species is nearly identical. Trees, however, have been reported to lose up to 80% of their foliage due to arborvitae leafminer and still survive. At least 27 species of parasites have been reported as natural enemies of arborvitae leafminers, the most significant of which may be a parasitic wasp (Pentacnemus bucculatricis). Arborvitae leafminer damage causes the tips of shoots and foliage to turn yellow and brown. If infestations are light, prune out infested tips.
• Azalea Sawflies: There are a few species of sawflies that impact azaleas. Johnson and Lyon's Insects that Feed on Trees and Shrubs mentions three of them. Amauronematus azaleae was first reported in New Hampshire in 1895 and is likely found in most of New England. Adults of this species are black with some white markings and wasp-like. Generally green larvae feed mostly on mollis hybrid azaleas. Remember, sawfly caterpillars have at least enough abdominal prolegs to spell “sawfly” (so 6 or more prolegs). Adults are present in May, and females lay their eggs and then larvae hatch and feed through the end of June. There is one generation per year. Nematus lipovskyi has been reared from swamp azalea (Rhododendron viscosum). Adults of that species have been collected in April (in states to the south) and May (in New England) and larval feeding is predominantly in late April and May in Virginia and June in New England. One generation of this species occurs per year, and most mollis hybrid azaleas can be impacted. A third species, Arge clavicornis, is found as an adult in July and lays its eggs in leaf edges in rows. Larvae are present in August and September. Remember, Bacillus thuringiensis Kurstaki does not manage sawflies.
• Bagworm: Thyridopteryx ephemeraeformis is a native species of moth whose larvae construct bag-like coverings over themselves with host plant leaves and twigs. This insect overwinters in the egg stage, within the bags of deceased females from last season. Eggs may hatch and young larvae are observed feeding around mid-June, or roughly between 600-900 GDD’s. Now is the time to scout for and remove and destroy any overwintered bags. In certain areas across MA in 2020, increased populations of bagworms were observed and reported, particularly in urban forest settings and managed landscapes. More information can be found here: https://ag.umass.edu/landscape/fact-sheets/bagworm
• Boxwood Leafminer: Monarthropalpus flavus partly grown fly larvae overwinter in the leaves of susceptible boxwood. Yellowish mines may be noticeable on the undersides of leaves. This insect grows rapidly in the spring, transforming into an orange-colored pupa. After pupation, adults will emerge and white colored pupal cases may hang down from the underside of leaves where adults have emerged. Adults may be observed swarming hosts between 300-650 GDD’s, or roughly the end of May through June. Most cultivars of Buxus sempervirens and B. microphylla are thought to be susceptible. If installing new boxwoods this spring, resistant cultivars such as ‘Vardar Valley’ and ‘Handsworthiensis’ are good choices at sites where this insect has been a problem.
• Boxwood Psyllid: Psylla buxi feeding can cause cupping of susceptible boxwood leaves. Leaf symptoms/damage may remain on plants for up to two years. English boxwood may be less severely impacted by this pest. Eggs overwinter, buried in budscales, and hatch around budbreak of boxwood. Eggs may hatch around 80 GDD’s. Foliar applications may be made between 290-440 GDD’s. However, the damage caused by this insect is mostly aesthetic. Therefore, no management may be necessary.
• Cankerworms: Alsophila pometaria (fall cankerworm) and Paleacrita vernata (spring cankerworm) are often confused for winter moth (Operophtera brumata). Cankerworm populations in eastern MA, particularly on areas of Cape Cod, were confused for winter moth in 2019. Spring cankerworm adults are active in February and March, and fall cankerworm adults are active in late November into early December. During these times, both species lay eggs. These native insects most commonly utilize elm, apple, oak, linden, and beech. Eggs of both species hatch as soon as buds begin to open in the spring. Caterpillars occur in mixed populations and are often noticeable by mid-May in MA. Young larvae will feed on buds and unfolding leaves. There are two color forms (light green and dark) for caterpillars of both species. Like winter moth, they will drop to the soil to pupate. This usually occurs in June. Fall cankerworm larvae have three pairs of prolegs (one of which is small so it is sometimes referred to as ½) and spring cankerworm have two pairs. (Winter moth caterpillars also have 2 pairs of prolegs.) If populations are large and damage is noticeable on hosts, reduced risk insecticides such as Bacillus thuringiensis Kurstaki or spinosad may target larvae between 148-290 GDD’s.
• Dogwood Borer: Synanthedon scitula is a species of clearwing moth whose larvae bore not only into dogwood (Cornus), but hosts also include flowering cherry, chestnut, apple, mountain ash, hickory, pecan, willow, birch, bayberry, oak, hazel, myrtle, and others. Kousa dogwood appear to be resistant to this species. Signs include the sloughing of loose bark, brown frass, particularly near bark cracks and wounds, dead branches, and adventitious growth. The timing of adult emergence can be expected when dogwood flower petals are dropping and weigela begins to bloom. Adult moth flights continue from then until September. Emergence in some hosts (ex. apple) appears to be delayed, but this differs depending upon the location in this insect’s range. Eggs are laid singly, or in small groups, on smooth and rough bark. Female moths preferentially lay eggs near wounded bark. After hatch, larvae wander until they find a suitable entrance point into the bark. This includes wounds, scars, or branch crotches. This insect may also be found in twig galls caused by other insects or fungi. Larvae feed on phloem and cambium. Fully grown larvae are white with a light brown head and approx. ½ inch long. Pheromone traps and lures are useful for determining the timing of adult moth emergence and subsequent management.
• Dogwood Sawfly: Macremphytus tarsatus larvae are commonly seen feeding on dogwoods, especially gray dogwood (Cornus racemosa). One generation occurs per year. The larvae of the dogwood sawfly overwinter in decaying wood and occasionally (rarely) compromised structural timber. An overwintering “cell” is created in this soft wood. Pupation occurs in the springtime and adults can take a lengthy time to emerge, roughly from late May through July. 100+ eggs are laid in groups on the underside of leaves. Eggs hatch and the larvae feed gregariously, initially skeletonizing the leaves. As the caterpillars grow in size, they are capable of eating the entire leaf, leaving only midveins behind. Larval appearance varies greatly throughout instars. Early instars are translucent and yellow, but as the caterpillars grow, they develop black spots (over the yellow) and become covered in a white powder-like material. Larvae and their shed skins may resemble bird droppings. Full-grown larvae begin to wander in search of a suitable overwintering location. Rotting wood lying on the ground is preferred for this. Sawfly caterpillars can be collected from plants and dropped into a can of soapy water.
• Eastern Tent Caterpillar: Malacosoma americanum eggs overwinter on host plant twigs. Egg hatch typically occurs when wild cherry leaves begin to unfold and young caterpillars may emerge by late-April through the first two weeks in May (90-190 GDD’s). Susceptible hosts include cherry and crabapple. Other host plants whose leaves are fed upon by this native insect can include apple, ash, birch, willow, maple, oak, poplar, and witch-hazel. Prune off and remove egg masses from ornamental host plants by early spring. Eastern tent caterpillars are native to Massachusetts and have many associated natural enemies (parasites and predators) that help regulate populations. Unless these caterpillars are actively defoliating specimen trees in a landscaped setting, we can coexist with this particular herbivore native to our forests.
• Elm Sack Gall Aphids: Tetraneura ulmi is a European aphid that was introduced into the United States in the 1890’s. This aphid is responsible for creating the pouch-like galls that we refer to as the “elm sack gall”. These leaf galls may be seen on red (slippery) elm (Ulmus rubra), American elm (Ulmus americana), and in the case of these photos, they have also been observed on camperdown elm (Ulmus glabra ‘Camperdownii’) on 6/1/2021 in Amherst, MA. The elm sack gall aphid uses certain species of grasses as alternate hosts, flying to grass where young aphids will then feed on their roots. (Another name for the elm sack gall aphid is the elm-grass root aphid.) The offspring of those generations will return to elm in the fall, where they will overwinter on the bark. Elm sack galls can be confused with elm cockscomb galls which are produced by a different aphid species (Colopha ulmicola). The galls created by that species look like their namesake – often a red cockscomb shaped gall on the upper surface of elm leaves. Typically, both of these species only cause aesthetic damage to elm and do not require management. However, the infestation noticed on this camperdown elm was significant when compared to previous years – leaves were swollen in size and heavy with galls, particularly on lower, shaded branches.
• Elongate Hemlock Scale: Fiorinia externa is found on eastern, Carolina, and Japanese hemlock, as well as yew, spruce, and fir. The elongate hemlock scale may overwinter in various life stages, and overlap of many developmental stages at any given time can be observed throughout much of the season. Treatments for the crawler, or mobile, stage of this insect may be made in late May through mid-June, or between 360-700 GDD’s, base 50°F. Nitrogen fertilizer applications may make elongate hemlock scale infestations worse.
• Euonymus Caterpillar: Yponomeuta cagnagella is of European origin and widespread in distribution throughout Europe. It was first reported in North America in Ontario in 1967. The euonymus caterpillars (larvae) feed in groups and envelop the foliage of the host plant in webs as they feed. Hosts include: Euonymus europaeus (tree form), E. kiautschovicus, E. alatus, and E. japonicus. Mature caterpillars are just under an inch in length, creamy yellow-gray in color with black spots and a black head capsule. By late June, these larvae pupate in white, oval-shaped cocoons which are typically oriented together vertically either on host plants or non-hosts in the area. Cocoons can be found in cracks and crevices, or webbed together leaves. The adult moth emerges in late June in most locations. The adult female secretes a gummy substance over her eggs which will harden, making them even more difficult to see. Eggs hatch by mid-August, at which time the tiny larvae prepare to overwinter beneath their eggshell-like covering. These larvae are inactive until the following year, when caterpillars group together to feed on newly emerging leaves, creating a mess of webs as they feed. There is one generation per year. Plants may be partially or entirely defoliated. Management of young, actively feeding caterpillars with Bacillus thuringiensis is possible if deemed necessary, however many species of Euonymus are considered invasive themselves.

Check out Episode 3 of InsectXaminer to see the euonymus caterpillar in action and learn more about its life cycle: https://ag.umass.edu/landscape/education-events/insectxaminer

• Euonymus Scale: Unaspis euonymi is an armored scale that can be found on euonymus, holly, bittersweet, and pachysandra. This insect can cause yellow spotting on leaves, dieback, and distorted bark. For crawlers, early June timing is suggested between 533-820 GDD’s. (Eggs begin to hatch in early June.)
• European Pine Sawfly: Neodiprion sertifer overwinters in the egg stage. Eggs are laid by females the previous season by cutting slits in needles using their ovipositors and depositing 6-8 eggs in each of 10-12 needles. Egg hatch occurs from late-April to mid-May and caterpillars become active roughly between 78-220 GDD, base 50°F. The primary host in MA is Mugo pine but it can be found on Scots, red, jack, and Japanese red pine. It is also found on white, Austrian, ponderosa, shortleaf, and pitch pine when planted near the aforementioned species. This dark colored caterpillar feeds in tight groups and small numbers can be pruned or plucked out of host plants and destroyed. Spinosad products can be used whenever the caterpillars are actively feeding, usually by mid-May and when caterpillars are still small. Bacillus thuringiensis kurstaki is not effective against sawflies.
• Fletcher Scale: Parthenolecanium fletcheri is a soft scale pest of yew, juniper, and arborvitae. Feeding scales, especially on yew, result in honeydew and sooty mold, needle yellowing, and at times, premature needle drop. There is one generation per year. Overwintered second instar nymphs can be targeted between 38-148 GDD’s, base50°F. Nymphs develop and adult females lay eggs (on average 500-600) in May that hatch by June. Dead females conceal egg masses beneath.Crawlers migrate short distances to branches and may be concentrated on certain branches of a particular plant.
• Forest Tent Caterpillar: Malacosoma disstria egg hatch occurs between 192-363 GDD’s, base 50°F, by mid-late May and caterpillars may be active for at least 5-6 weeks following. Susceptible hosts whose leaves are fed on by this insect include oak, birch, ash, maple, elm, poplar, and basswood. This native insect has many natural enemies, including some very effective pathogens that typically regulate populations. However, outbreaks of this insect can occur on occasion.
• Hemlock Looper: Two species of geometrid moths in the genus Lambdina are native insects capable of defoliating eastern hemlock, balsam fir, and white spruce. Adult moths lay their eggs on the trunk and limbs of hosts in September and October, and eggs will hatch by late May or early June. (L. fiscellaria caterpillars may be active between 448-707 GDD’s.) Monitor susceptible hosts for small, inch-worm like caterpillars. Where populations are low, no management is necessary. Hemlock loopers have several effective natural enemies.
• Hemlock Woolly Adelgid: Adelges tsugae is present on eastern and Carolina hemlock. The overwintering hemlock woolly adelgid generation (sistens) is present through mid-spring and produces the spring generation (progrediens) which will be present from early spring through mid-summer. HWA, unlike many other insects, does most of its feeding over the winter. Eggs may be found in woolly masses at the base of hemlock needles beginning in mid-March. Each woolly mass is created by a female who may then lay 50-300 eggs. Eggs hatch and crawlers may be found from mid-March through mid-July. Infested trees may be treated with foliar sprays in late April to early May, using Japanese quince as a phenological indicator. Systemic applications may be made in the spring and fall, or when soil conditions are favorable for translocation to foliage. Nitrogen fertilizer applications may make hemlock woolly adelgid infestations worse.
• Holly Leafminers: Seven species of leaf miners feed on holly. Phytomyza ilicicola is usually referred to as the native holly leafminer. This species is known to feed on Ilex opaca, I. crenata, and related cultivars; however, it only lays its eggs in American holly (Ilex opaca). Some research suggests that the native holly leafminer may lay its eggs in other Ilex species, but that the larvae are unable to complete their development. This insect is found throughout the native range of its host plants. Larvae overwinter in leaf mines and pupation occurs in March and April and adult emergence by mid-May (192-298 GDD’s, base 50°F). Adult flies are known to emerge over a period of 6 or so weeks in the spring. Females lay eggs using their ovipositor on the underside of newly formed leaves. A tiny green blister forms on the leaf as the first symptom of injury. Larvae hatch from the egg and create a narrow mine that may appear brown from the upper leaf surface. Mines are broadened in the fall and a large blotch is completed in the winter. Larvae are yellow maggots and reach 1.5 mm. in length when mature. Current year’s mines are easily overlooked due to the slow feeding patterns of the larvae. Premature leaf drop may occur. Remove and destroy mined leaves before May. Phytomyza ilicis is usually only referred to as the holly leafminer, and it is a non-native species introduced from Europe and only feeds on Ilex aquifolium. (The native holly leaf miner does not develop in I. aquifolium.) The biology and damage this insect causes is similar to that of the native holly leafminer, with the exception of the fact that eggs are laid in the midvein of the leaf and young larvae tunnel in the vein until the fall. Remove and destroy mined leaves before May. Adults may be present mid-late May (246-448 GDD’s, base 50°F).
• Honeylocust Plant Bug: Diaphnocoris chlorionis feeding results in tiny yellowish-brownish spots on leaves, leaf distortion, and in some cases, defoliation. (There are at least 7 species of plant bugs that feed on honeylocust, Gleditsia triacanthos.) There is one generation per year. Immatures and adults feed on foliage and light to moderately damaged foliage may persist throughout the growing season. Honeylocust plant bugs overwinter as eggs laid just beneath the bark surface of 2 and 3 year old twigs. Eggs hatch just after vegetative buds of the host begin to open. Young nymphs crawl to the opening leaflets and begin feeding and the most significant damage occurs at that time, when the insect is hidden from view. Nymphs develop into adults around May-July. This insect can be targeted between 58-246 GDD’s, base 50°F.
• Imported Willow Leaf Beetle: Plagiodera versicolora adult beetles overwinter near susceptible hosts. Adult beetles will chew holes and notches in the leaves of willow once they become available. Females lay yellow eggs in clusters on the undersides of leaves. Larvae are slug-like and bluish-green in color. They will feed in clusters and skeletonize the leaves. Most plants can tolerate the feeding from this insect, and foliage will appear brown. Repeated yearly feeding can be an issue, in which case management of the young larvae may be necessary. Take care with treatment in areas near water.

Check out Episode 4 of InsectXaminer to see the imported willow leaf beetle in action and learn more about its life cycle: https://ag.umass.edu/landscape/education-events/insectxaminer

• Lacebugs: Stephanitis spp. lacebugs such as S. pyriodes can cause severe injury to azalea foliage. S. rhododendri can be common on rhododendron and mountain laurel. S. takeyai has been found developing on Japanese andromeda, leucothoe, styrax, and willow. Stephanitis spp. lace bug activity should be monitored through September. Before populations become too large, treat with a summer rate horticultural oil spray as needed. Be sure to target the undersides of the foliage in order to get proper coverage of the insects. Certain azalea and andromeda cultivars may be less preferred by lace bugs.
• Lecanium Scales (Oak): Parthenolecanium quercifex overwinters as a second instar nymph on oak twigs. Females feed and mature in the spring, from mid-April to early May and eggs may be laid between late May and into June. Eggs hatch in June or early July and crawlers migrate to host plant leaves where they spend the summer and migrate as second instars back to host plant twigs in the fall.
• Lilac Borer: Podosesia syringae is a clearwing moth pest of lilac, privet, fringetree, and ash. (It is also known as the ash borer, not to be confused with the emerald ash borer.) Adults mimic paper wasps. Larvae are wood-boring, and signs and symptoms include branch dieback, holes, and occasionally, sawdust-like frass accumulated on bark. Larvae bore into stems, trunks, and branches, chewing an irregularly shaped entrance hole. Peak adult moth flights may occur in the northern portion of this insect’s range in June and is usually over by August 1^st. Pheromone traps can be used to time adult emergence. Adult females lay flattened, oval, and tan eggs that are deposited singly or in clusters on bark crevices, ridges, and sometimes smooth bark; but usually laid in or near wounds in the bark. On average, 395 eggs are laid by each female. After hatch, larvae chew into the bark and feed laterally and then vertically in phloem tissue. Larvae overwinter in tunnels in the final instar and resume feeding in the spring. Adults emerge through a round exit hole (4-5 mm. in diameter). This insectmay be targeted between 200-299 GDD’s, base 50°F.
• Lily Leaf Beetle: Lilioceris lilii adults overwinter in sheltered places. As soon as susceptible hosts such as Lilium spp. (Turk’s cap, tiger, Easter, Asiatic, and Oriental lilies) and Fritillaria spp. break through the ground, the adult lily leaf beetles are known to feed on the new foliage. (Note: daylilies are not hosts.) Typically, in May, mating will occur and each female will begin to lay 250-450 eggs in neat rows on the underside of the foliage. If there are only a few plants in the garden, hand picking and destroying overwintering adults can help reduce local garden-level populations at that time.

Check out Episode 3 of InsectXaminer to see the lily leaf beetle in action and learn more about its life cycle: https://ag.umass.edu/landscape/education-events/insectxaminer

• Magnolia Scale: Neolecanium cornuparvum overwinters as first instar nymphs which are elliptical, and dark slate gray in color and can usually be found on the undersides of 1 and 2 year old twigs. Nymphs may molt by late April or May and again by early June at which time the scales may be purple in color. Eventually nymphs secrete a white powdery layer of wax over their bodies.
• Rhododendron Borer: Synanthedon rhododendri is one of the smallest of the native clearwing moths. Rhododendrons are preferred hosts, although mountain laurel, and deciduous azaleas can be heavily infested, especially if they are planted in close proximity to rhododendrons. Injury may be first noticed in the fall (leaves lose their sheen, then become pale green, then olive, then chlorotic) and can look similar to drought stress. On branches that seem to be stunted, look at limb crotches, scars, and other irregularities for sawdust stuck on bark or on the ground beneath these areas. In late May and early June, holes may contain pupal shed skins extending halfway out. Moth emergence occurs in the late-spring, early-summer. After mating, female moths seek out suitable egg laying locations (preferring wounded areas or limb crotches). The female lays her eggs and dies. Eggs hatch and larvae tunnel into the inner bark where they feed in tunnels that become packed with reddish frass pellets. By late fall, larvae move to the sapwood where they overwinter and resume feeding by mid-March. Pupation occurs in the spring and there is one generation per year. Prune out and destroy infested branches before late May/June. Monitor for adults in mid-May (192-298 GDD’s, base 50°F).
• Snowball Aphid: Neoceruraphis viburnicola eggs overwinter on viburnum twigs and buds. Eggs hatch and this aphid becomes active on certain species of viburnum roughly between 148-298 GDD’s or around redbud bloom. This insect is particularly noticeable on V. opulus, V. prunifolium, and V. acerifolia. Stem mothers, appearing blueish-white, can be found in curled up and distorted foliage. Damage caused by this insect pest is mostly aesthetic. At this time, the damage from this insect has already occurred, so management for this season is no longer possible.
• Spruce Bud Scale: Physokermes piceae is a pest of Alberta and Norway spruce, among others. Immatures overwinter on the undersides of spruce needles, dormant until late March. By April, females may move to twigs to complete the rest of their development. Mature scales are reddish brown, globular, 3 mm. in diameter, and found in clusters of 3-8 at the base of new twig growth. They closely resemble buds and are often overlooked. Crawlers are present around June.
• Spruce Spider Mite: Oligonychus ununguis is a cool-season mite that becomes active in the spring from tiny eggs that have overwintered on host plants. Hosts include spruce, arborvitae, juniper, hemlock, pine, Douglas-fir, and occasionally other conifers. This particular species becomes active in the spring and can feed, develop, and reproduce through roughly June. When hot, dry summer conditions begin, this spider mite will enter a summer-time dormant period (aestivation) until cooler temperatures return in the fall. This particular mite may prefer older needles to newer ones for food. Magnification is required to view spruce spider mite eggs. Tapping host plant branches over white paper may be a useful tool when scouting for spider mite presence. (View with a hand lens.) Spider mite damage may appear on host plant needles as yellow stippling and occasionally fine silk webbing is visible.

Spruce spider mite populations may again build (with subsequent generations) in mid-late May (192-363 GDD’s) and again in late August to mid-September (2375-2806 GDD’s). Continue to scout for spruce spider mite by tapping branches over a white piece of paper or other white surface, then viewing them with a hand lens or other magnification. A general rule of thumb is that if 10 or more spruce spider mites are found per branch (in the absence of predatory mites), chemical management might be necessary (if you are also seeing roughly 10% of the foliage with stippling/discoloration). However, if you are finding light-colored and tear-drop shaped and fast-moving predatory mites, at a ratio of approximately 1 predatory mite: 10 spruce spider mites, these beneficial insect relatives may be able to help naturally keep spruce spider mite populations below damaging levels. It is important to also scout for predatory mites and beneficial insects (hover fly larvae, lacewing larvae, and lady beetle larvae and adults) while scouting for spruce spider mite, because knowledge of the presence of these beneficial predators will impact your management decisions. Broad spectrum insecticides/miticides should not be used to manage spruce spider mite on host plants where predatory mites are present as these chemicals could kill the predatory mites and lead to a subsequent surge in spruce spider mite populations.

• Taxus Mealybug: Dysmicoccus wistariae will produce honeydew and lead to sooty mold growth, yellowing of needles, and sparsely foliated plants. Eventual dieback may be possible. This species is commonly associated with taxus in New England, but can be occasionally found on dogwood, rhododendron, Prunus spp., maple, andromeda, and crabapple. These mealybugs are found on stems and branches and particularly like to congregate at branch crotches. Taxus mealybug feeds in the inner bark tissue of the trunk and branches. Adult females are present from June to August and give birth to living young in the summer. Immatures overwinter. A single generation may occur per year in New England, but areas to the south can have multiple generations of this insect. Management may be targeted between 246-618 GDD’s, base 50°F. Horticultural oil and neem oil may be used.
• Twolined Chestnut Borer: Agrilus bilineatus is a native jewel beetle (also known as a flatheaded borer) in the Family Buprestidae. This insect is also in the same genus as the invasive emerald ash borer. The twolined chestnut borer is native to Massachusetts, much of New England, and the eastern United States. This species has one generation per year and adults are typically active from April – August, depending upon location and temperature. Adults will conduct some maturation feeding on oak prior to mating. Females will lay clusters of tiny eggs in the cracks and crevices of bark. Larvae hatch from the eggs in 1-2 weeks and burrow through the bark into the cambium, where they feed in a similar manner to the emerald ash borer, creating meandering galleries as they feed. (The galleries of the twolined chestnut borer can be straight in very stressed trees.) Larvae typically mature by August – October and burrow to the outer bark where they create a chamber in which they overwinter. Pupation occurs the following spring and adults emerge through D-shaped exit holes that are approximately 1/5 inch wide. In the northern extent of this insect’s range, they can take 2 years to complete their life cycle. Larvae of this insect have been recorded from eastern white oak, common post oak, burr oak, scarlet oak, northern red oak, and eastern black oak. Adults have been recorded on fir and pin oak. These insects are attracted to stressed host plants and typically become a secondary factor in the decline of the tree.
• Two-Spotted Spider Mite: Tetranychus urticae is a “warm-season” mite that loves hot and dry weather, which may favor the quick reproduction and build-up of this pest. Management should seek to preserve beneficial predatory mites. Monitor susceptible hosts (elm, maple, redbud, ash, black locust, tuliptree, and many deciduous shrubs) for increasing numbers of these mites until mid-August. Mites will be found on the undersides of leaves and cause stippling of the foliage.

• Viburnum Leaf Beetle: Pyrrhalta viburni is a beetle in the family Chrysomelidae that is native to Europe, but was found in Massachusetts in 2004. Viburnum leaf beetle overwinters as eggs laid in capped pits on the newest growth of susceptible viburnum branches. Scout for overwintered eggs and prune out and destroy before they hatch. Egg hatch occurs in late-April to early-May as temperatures warm and foliage becomes available. Monitor for larvae in mid-May (80-120 GDD’s). This beetle feeds exclusively on many different species of viburnum, which includes, but is not limited to, susceptible plants such as V. dentatum, V. nudum, V. opulus, V. propinquum, and V. rafinesquianum. Some viburnum have been observed to have varying levels of resistance to this insect, including but not limited to V. bodnantense, V. carlesii, V. davidii, V. plicatum, V. rhytidophyllum, V. setigerum, and V. sieboldii. More information about viburnum leaf beetle may be found at http://www.hort.cornell.edu/vlb/ .
• Woolly Apple Aphid: Eriosoma lanigerum may be found on apple, crabapple, hawthorn, mountain-ash, Pyracantha, and elm hosts. The primary (winter) host is elm, on which aphids infest emerging spring leaves, causing leaves to curl or close into stunted, rosette-like clusters found at twig tips. Woolly apple aphid was observed on elm on 6/1/2021 in Amherst, MA. Rosettes at this location are full of honeydew producing aphids. On apple and crabapple, this species of aphid colonizes roots, trunks, and branches in the summer and is commonly found near previous wounds or callous tissue. On roots, the aphids cause swelled areas which can girdle and kill roots. The aphids, when found in above ground plant parts such as elm leaves, are covered with white wax. Eggs are the overwintering stage on elm, which hatch in the spring in time for the nymphs to infest new elm foliage. Following a few generations on elm, the aphids will develop into a winged form, which will disperse and seek out apple and crabapple. Multiple generations will occur on these alternate hosts in the summer and by the fall, a winged form will return to elm and mated females will lay eggs near elm buds. These aphids are a favorite snack for insect predators such as the multicolored Asian lady beetle, Harmonia axyridis.

• Woolly Beech (Leaf) Aphid: Phyllaphis fagi is a species of aphid commonly found on the leaf undersides of European beech, Fagus sylvatica, and its cultivars. This is a European species that is now widely distributed throughout North America. All life stages of this particular aphid occur on European beech foliage. European beech trees in North America have been observed as capable of holding large populations of this aphid year after year with little to no visible injury to the tree. Like their other aphid brethren, the woolly beech leaf aphid can create large quantities of sticky honeydew. These aphids were observed on Fagus sylvatica 'Asplenifolia' in Amherst, MA on 6/1/2021. The woolly beech leaf aphid is sometimes confused with another woolly aphid, also known as the beech blight aphid (Grylloprociphilus imbricator), which is only found on American beech, Fagus grandifolia. G. imbricator has an alternate common name, the boogie-woogie aphid, due to a behavior where this species, when colonies are disturbed, can wiggle (or dance) together, perhaps in an effort to distract potential predators.

• Woolly Elm Aphid: Eriosoma americanum females lay a single egg in the cracks and crevices of elm bark, where the egg overwinters. Eggs hatch on elm in the spring as leaves are unfolding. Aphids may be active from 121-246 GDD’s, base 50°F on elm. A young, wingless female hatched from the egg feeds on the underside of leaf tissue. This female aphid matures and gives birth to 200 young, all females, without mating. These aphids feed, and the elm leaf curls around them and protects them. By the end of June, winged migrants mature and find serviceberry hosts. Another set of females is produced. These new females crawl to and begin feeding on the roots of serviceberry. Multiple generations occur on the roots of serviceberry through the summer.

Concerned that you may have found an invasive insect or suspicious damage caused by one? Need to report a pest sighting? If so, please visit the Massachusetts Introduced Pests Outreach Project: http://massnrc.org/pests/pestreports.htm .

Reported by Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program

Weeds

Inspect areas of the landscape where new trees or shrubs, especially those that were field grown, have been planted in the last year. Look for perennial weeds that may be growing from the root ball. Canada thistle, mugwort, quackgrass, bindweed and horsenettle are some of the likely culprits. Perennial weeds can be spot treated with glyphosate products.

Many landscape trees commonly produce vegetative suckers at their trunk base. Suckers are commonly seen on crabapple, flowering cherry, flowering pear, plum, linden, maple and sometimes oak. Honeylocust commonly produces vegetative sprouts along the entire length of their trunk. It these suckers or sprouts are not controlled, the landscape will be a contender for the “Shabby Landscape Award”. Pruning is effective but very time consuming. Another option would be use the product Scythe that contains pelargonic acid to remove these vegetative suckers and sprouts when they are very small. Very small means less than one inch in length. Pelargonic acid is a contact herbicide. If Scythe is applied to small suckers and sprouts the product will desiccate them and physical removal will not be required. Larger growth will first need to be physically removed and then Scythe can be used as a maintenance program. Products that contain glyphosate should not be used as glyphosate is a translocated herbicide and injury to the whole plant is possible.

Do not attempt to control Japanese knotweed, Polygonum cuspidatum, currently as herbicide applications are not effective. In preparation for a late season herbicide application, cut or mow stands of knotweed to the ground in late May and early June. This practice is done to facilitate herbicide application by removing the dried stems from the previous year’s growth and will control plant height so knotweed will be shorter at time of treatment in late summer. There is also some indication that the plant’s carbohydrate reserves may be reduced with this early season mowing.

I worked with an Extension Specialist for another state on an issue related to the herbicide dichlobenil. The herbicide dichlobenil, sold under the tradenames Barrier and Casoron, is used for the control of several difficult to control perennial weeds in the landscape and nursery setting. It is applied from late fall to early spring. Product label cautions about the use in this herbicide in landscapes that are upslope of turf areas since rainfall can wash the herbicide into the turf resulting in severe injury or death. The situation was just that, movement of dichlobenil into an adjacent lawn after a sizable snowfall followed by rapid melting. Before the problem was diagnosed, dead turf areas were reseeded. Turf seed did not germinate or establish. At this point, it is simply a waiting game until the herbicide degrades. I suggested that periodically a handful of perennial ryegrass seed be scattered on the area and incorporated into the soil. When germination is observed the area can be safety seeded with a high rate of turf seed. Dichlobenil is a very effective herbicide for the control of certain weeds that are not controlled by other herbicides or physical removal. Extension Weed Specialists continually encourage landscape and turf professionals to “Read, Understand and Follow the Product Label”. This is especially important with herbicides such as dichlobenil.

Report by Randy Prostak, Weed Specialist, UMass Extension Landscape, Nursery and Urban Forestry Program

Landscape Practices

Mulch 101

The Benefits of Mulching

Mulching is a common landscape practice for a reason; it can benefit plant and soil health along with providing aesthetic appeal. It is important to apply mulch appropriately, applying mulch no more than a 1-3” thick layer. Mulch over the root ball of plants should be minimal, only 1-2”, and mulch should not be touching stems or trunks.

Benefits of applying wood-product mulches:

· Reduces evaporation from the soil surface (increasing soil moisture)

· Increases soil organic matter as decomposition occurs thus improving soil structure and drainage as well as encouraging mycorrhizal activity

· Encourages beneficial soil organisms

· Suppresses weed growth (although weed seeds can blow in and germinate on the mulch surface)

· Reduces erosion

· Acts as an insulator, helping to moderate soil temperature, protecting plant roots

· Helps prevent mechanical damage from mowers and string trimmers that can occur when grass grows next to plants

It is generally best practice to avoid inorganic mulches. Stone and gravel can absorb or reflect heat which can damage plants and do not provide benefits to the soil like bark mulches. They can also make amending the soil difficult and can eventually sink down into the soil. Plastic mulches also don’t provide any benefits to the soil.

Avoiding Mulch Volcanoes

When it comes to mulch there is such a thing as too much of a good thing. Too frequently mulch is applied in excessive amounts, either directly around the base of plants or around landscape beds in general. “Mulch volcanoes”, which is mulch mounded around the base of plants, can have many negative impacts on plant health. When mounded around the base of plants, mulch can result in excessive moisture leading to decay along with predisposition to insect and disease problems. Secondary root formation can also occur, which is the formation of roots above the trunk flare in the mulch areas. These roots often circle the trunk, gradually girdling the tree if not carefully removed. When mulch is applied too thickly throughout the landscape bed it can have contrasting negative impacts on water movement through the mulch and to the soil. In some cases, the thick mulch absorbs and holds the water, preventing it from infiltrating to the soil and leaving it unavailable for plant uptake. Other times, the water does infiltrate to the soil but the thick mulch layer prevents evaporation from occurring, leading to the soil staying too wet leading to rot problems and reduced oxygen in the soil.

Potential Problems

Sour mulch and fungi can be unpleasant problems resulting from wood-product mulch applications. Sour mulch is a problem that occurs during production and is the result of mulch being piled too high. In very large piles compaction and heating can occur at the base of the pile, resulting in anaerobic conditions and the buildup of organic acids which can lower the pH of the mulch. When sour mulch is applied in the landscape it can lead to the rapid decline of plant material and a foul smell. If sour mulch is unknowingly applied to the landscape, spreading the mulch thin and watering heavily can leach the toxins. Sour mulch should also be moved away from plants to avoid damage. It is important when developing mulch or wood chip piles to make sure they are not piled higher than 10’.

Fungi such as slime molds, bird’s nest fungi, artillery fungus, stinkhorns, and mushrooms are often found in mulches. These fungi are associated with mulches because of the decomposition of the mulch. In general, these fungi are not harmful to plants, and are not associated with health hazards unless consumed. Most of these fungi are just visual nuisances. Artillery fungus however can be a problem as expelled spore masses can stick to homes and vehicles, and are difficult to remove. When removed they can leave a stain. These fungi are most prevalent with moist rotting mulch especially in cool northern facing locations. Disturbing the mulch in areas that are conducive to artillery fungus can help dry out the area and make it less ideal for the fungus. Replacing mulch and freshening mulch can also help.

Sources:

Kujawski, R. and D. Swanson. 2011. Sour Mulch. UMass Extension.

Pettinelli, D. Mulch Basics. University of Connecticut.

Smith, T. 2011. Fungi in Mulches and Composts. UMass Extension.

The Morton Arboretum. Mulching trees and shrubs.

Report by Mandy Bayer, Extension Assistant Professor of Sustainable Landscape Horticulture, UMass Stockbridge School of Agriculture

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