Landscape Message: May 21, 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 May. The next message will be posted on May 28. To receive immediate notification when the next Landscape Message update is posted, be sure to join our e-mail list 

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Scouting Information by Region

Environmental Data

The following data was collected on or about May 21, 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	74	163.5	61	58	0.01	12:00 PM 5/19
SOUTHEAST	65.5	188	78	60	0.06	3:00 PM 5/19
NORTH SHORE	78	207.5	60	55	0.00	10:30 AM 5/19
EAST	88	229	68	62	0.00	5:00 PM 5/19
METRO	74.5	205	57	54	0.04	6:00 AM 5/19
CENTRAL	85.5	219	64	62	0.14	7:30 AM 5/19
PIONEER VALLEY	82.5	218	63	58	0.04	11:30 AM 5/19
BERKSHIRES	54	133.5	59	54	0.00	8:00 AM 5/19
AVERAGE	75	195	64	58	0.04	_
n/a = information not available

Check the drought status as of 5/18 here: https://droughtmonitor.unl.edu/CurrentMap/StateDroughtMonitor.aspx?MA

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.
Enkianthus campanulatus (redvein enkianthus)	*	*	*	Begin	*	Begin	Begin/Full	Begin
Rhododendron catawbiense (Catawba rhododendron)	Begin	Begin/Full	Full	Begin	*	Begin	Begin	*
Deutzia spp. (Deutzia species)	Begin	Full	Begin	Begin	Begin	Begin	Begin/Full	Begin
Aesculus hippocastanum (common horsechestnut)	begin/Full	Begin	Full	Begin	Begin	Begin	Full	Full
Rhododendron carolinianum (Carolina rhododendron)	Begin/Full	*	Full	Full	Begin	*	Begin/Full	Begin
Spiraea x vanhouttei (Vanhoutte spirea)	Full	Full/End	Full/End	Begin/Full	Full	Begin	Full	Begin
Elaeagnus umbellata (autumn-olive)	Full	Full	Full	Full	Full	Full	Full	*
Syringa vulgaris (common lilac)	Full	Full	Full	Full/End	Full/End	Full/End	Full	Full
Cornus florida (flowering dogwood)	Full	Full/End	Full/End	Full/End	Full	Begin/Full	Full	Full
Rhododendron spp. (early azaleas)	Full/End	Full	Full	Full	Full	Full	Full/End	Full
* = no activity to report/information not available

Regional Notes

Cape Cod Region (Barnstable)

General Conditions: The average temperature for the period from May 12 – May 19 was 61˚F with a high of 79˚F on May 18 and a low of 40˚F on May 13. The daytime highs have been above normal for the Cape at this time of the year. The period has been dominated by mostly sunny days with no precipitation. Soil moisture is low and the ten-day forecast does not look promising for precipitation. Herbaceous plants seen in bloom during the period include columbine, creeping phlox, bloodred geranium, yellow alyssum, fringed bleeding heart, mayapple, merry bells, Solomon’s seal, lily of the valley, vinca vine, star of Bethlehem, chives, some early bearded iris, the last of the daffodils are passing and the tulips are not far behind. Woody plants in bloom include crabapples, redbud, flowering cherry ‘Kwanzan’, blueberry, chokeberry, kerria, dwarf fothergilla, koreanspice viburnum, cherry laurel, wisteria, beach plum, and the oaks have begun their deluge of pollen.

Pests/Problems: The most common problems in the landscape are still related to last year’s drought or secondary pathogens as a result of the drought conditions; rhododendron and arborvitae damage being the most common. Armillaria was found causing damage to privet. Armillaria is often found as a secondary pest on drought stressed woody plants. As far as foliar diseases go, the lack of precipitation is keeping those organisms at bay for the time being and I have seen several sycamores that look a lot better than they did in recent years with only minor anthracnose. Insects pests seen this week include spruce spider mite on Alberta spruce, Japanese maple scale on privet, white prunicola scale on lilac, lecanium scale on white oak, iris borer on bearded iris, columbine leafminer on columbine, hydrangea leaftier on smooth hydrangea, and aphids on several species. Invasive plants in bloom include burning bush, autumn olive, bush honeysuckles, garlic mustard, and cypress spurge. Weeds in bloom include common violet, dandelion, buttercup, narrowleaf plantain, red sorrel, and black medic. The winter annuals are quickly passing and dispersing seed with the warm weather. Some turf is already showing some slight signs of water stress on droughty slopes. There is a little bit of red thread and a lot of weedy lawns where turf was damaged last year. Almost everybody on the Cape has a rabbit problem. Deer ticks and dog ticks are abundant.

Southeast Region (Dighton)

General Conditions: Among the many plants in flower I've noticed these: Alliaria petiolata (garlic mustard), Allium (flowering onion), Aquilegia (columbine), Arisaema triphyllum (Jack in the pulpit), Aesculus hippocastanum (horse chestnut), Aurinia saxatilis (basket of gold), Barbarea vulgaris (yellow rocket), Cercis canadensis (redbud), Chelidonium majus (greater celandine), Conium maculatum (poison hemlock), Convallaria majalis (lily of the valley), Cornus florida (flowering dogwood), C. sericea (redtwig dogwood), Deutzia, Elaeagnus umbellata (autumn olive), Euonymus alatus (winged euonymus, burning bush), Euphorbia epithymoides (yellow/cushion spurge), Fothergilla major (mountain witch alder), Geranium maculatum (wild geranium), G. sanguineum (cranesbill geranium), Halesia carolina (Carolina silverbell), Hesperis matronalis (dame's rocket),Hyacinthoides hispanica (wood hyacinth), Hydrangea arborescens 'Annabelle', Ilex x meserveae (blue holly), Iris germanica (German iris), Kerria japonica 'pleniflora', Lamprocapnos spectabilis (bleeding heart), Lonicera morrowii (Morrow's honeysuckle), Lunaria annua (honesty), Lupinus (lupine), Magnolia x soulangeana, Malus (apples, crabapples), Myosotis (forget-me-not), Narcissus 'Actaea' (poeticus daffodil), Osmunda claytoniana (interrupted fern), Ornithogalum (star of Bethlehem), Paeonia (herbaceous peony), Papaver orientale (Oriental poppy), Paulownia elongata (empress tree), Phlox subulata (creeping phlox), Polygonatum biflorum (Solomon's seal), Prunus laurocerasus (cherry laurel), P. martima (beach plum), P. serrulata (Kwanzan cherry), Pulmonaria (lungwort), Vaccinium corymbosum (highbush blueberry), Viburnum burkwoodii (Burkwood viburnum) V. plicatum, (double-file viburnum), Viola papilionacea (common blue violet), V. tricolor (Johnny-jump-up), Vinca minor (periwinkle), Ranunculus repens (creeping buttercup), Rheum rhabarbarum (rhubarb), Rosa rugosa (beach rose), Rhododendron catawbiense, R. vasei, R. 'Cunningham's White', (evergreen and semi-evergreen azaleas), Spiraea prunifolia (bridal wreath spirea), Syringa vulgaris (common lilac), S. x persica (Persian lilac), Tulipa, Trillium erectum (wake robin).

Pests/Problems: In the past week, I observed: Pine Needle Scale crawlers on mugo pine, Juniper Scale crawlers on Juniper chinensis 'Grey Owl', European Pine Sawfly larvae on mugo pine, Leaf Roller on grape 'Concord', and Eastern Tent Caterpillar on black cherry. I discovered a number of last year's bagworm on burning bush. Bags of overwintered bagworm eggs from last season's generation will give rise to this year's caterpillars. We are north of their ordinary range. Ticks continue to be a serious problem. I can't recall a season where I've noticed so many. This may only be an anecdotal account but I'm truly intimidated. Pay close attention to children and pets as they are most at risk. We are likely in the initial stages of a drought. The showers we've had produced very little moisture which quickly evaporated. Things are dry now and over the next ten days there is no substantial relief predicted to be in sight.

North Shore (Beverly)

General Conditions: There was a shift in the weather this period from below average for this time of the year to above average. Daytime temperatures ranged from low 70s to 80s and nighttime temperatures range from mid 40s to low 50s. The average daily temperature was 62˚F with the highest temperature of 81˚F recorded on May 18 and the lowest temperature of 45˚F recorded on May 13. Dry conditions persisted as there was no precipitation recorded at Long Hill during this period. However, grass on lawns is green and many plants are in bloom with beautiful displays of color in the landscape. Woody plants seen in bloom include: silver bell (Halesia carolina), Wright viburnum (Viburnum wrightii), handkerchief or dove tree (Davidia involucrata), beach plum(Prunus maritima), large fothergilla (Fothergilla major), dwarf fothergilla (Fothergilla gardenii), wisteria (Wisteria floribunda), pearlbush (Exochorda racemosa), flowering dogwood (Cornus florida), redbud (Cercis canadensis), little leaf lilac (Syringa microphylla), common lilac (Syringa vulgaris), common horse chestnut (Aesculus hippocastanum), golden chain tree (Laburnum anagyroides), Scotch laburnum (Laburnum alpinum), tree peony (Paeonia suffruticosa), Alabama snow wreath (Neviusia alabamensis) Carolina rhododendron (Rhododendron carolina), Catawba rhododendron (Rhododendron catawbiense), many azaleas, single seed hawthorn (Crataegus monogyna), crabapple (Malus spp.), and highbush blueberry (Vaccinium corymbosum). Herbaceous plants seen in bloom include: Scotch rose (Rosa spinosissima), Father Hugo rose (Rosa hugonis), honesty plant (Lunaria annua), yellow archangel (Lamiastrum galeobdolon), blue eyed Mary (Omphalodes verna), vinca vine (Vinca minor), water forget-me-not (Myosotis palustris), barrenwort (Epimedium rubrum), trilliums (Trillium spp.), corydalis (Corydalis lutea), bleeding heart (Dicentra spectabilis), and tulips(Tulipa spp.)

Pests/Problems: Due to the dry conditions, some of the perennial plants on exposed dry sandy soils are starting to show signs of water stress. We need rain!. Ticks are very active. Make sure you apply repellents before going to work outdoors. Dandelion (Taraxacum officinale) seeds are maturing and are being blown over the landscape by wind. Other spring weeds seen in bloom include: violets (Viola spp.), ground ivy (Glechoma hederacea) garlic mustard (Alliaria petiolata) and dead nettle (Lamium purpureum). Take measures to control weeds before they set seed.

East Region (Boston)

General Conditions: So much for the early May precipitation alleviating the dry soil conditions. We have not received any rainfall since May 10, new plantings require supplemental irrigation. We reached 81˚F on May 18. The average first 80-degree day is May 25; in 2020 we hit 80 on May 4. Many plants are in bloom such as Aesculus hippocastanum (horse chestnut), Cornus sericea (redtwig dogwood), Prunus laurocerasus ‘Otto Luyken’ (cherry laurel) and wisteria. With its unusual large red panicle flowers; Aesculus pavia (red buckeye) is an underutilized, eye-catching landscape plant.

Pests/Problems: Zero precipitation over the past week is never a good way to start the report! Viburnum Leaf Beetle larvae continue to feed on Viburnum foliage. Sewn up hydrangea terminal foliage should be removed and disposed of offsite in an attempt to interrupt the Hydrangea Leaftier yearly cycle. Aphids are prevalent on Rosa spp. and Viburnum carlesii in particular. Swarms of what are likely boxwood leafminer adults can be seen hovering around Buxus sp. (boxwood). Adults of these species typically emerge by the end of May, beginning of June, or roughly between 330 - 650 GDDs. Rhododendrons continue to show signs of previous stress. Dead branches and fungal leafspot are common throughout the landscape. Fungal leaf spot has been observed on otherwise healthy Aronia spp. (chokeberry) and Populus spp. (hybrid poplars). Weeds are flourishing; garlic mustard (Alliaria petiolata) continues to flower, Japanese knotweed (Fallopia japonica) is 4 feet tall and crabgrass (Digitaria spp.) has emerged in vacant sunny locations. The air is thick with pollen.

Metro West (Acton)

General Conditions: As with any spring, the landscape is exploding with color and observed in some stage of bloom this past week were the following woody plants: Aesculus × carnea 'Briotii' (red horse chestnut), Aesculus hippocastanum (horse chestnut), Aronia arbutifolia (black chokecherry), Cercis canadensis (redbud), C. canadensis ‘Alba’ (white flowering redbud), Cornus florida (dogwood), C. x rutgersensis 'Ruth Ellen' (Rutgers Hybrid Dogwood), Crataegus spp. (hawthorn), Daphne x burkwoodii ‘Carol Mackie’ (Carol Mackie daphne), Fothergilla gardenii (dwarf fothergilla), F. major (large fothergilla), Halesia carolina ‘Arnold Pink’ (Arnold Pink silverbell), Halesia tetraptera (mountain silverbell), Ilex aquifolium (English holly), Kerria japonica (Japanese kerria), Kerria japonica 'Pleniflora’ (double-flowered Japanese kerria), Leucothoe axillaris (coast leucothoe), Magnolia 'Elizabeth' (Elizabeth magnolia), Malus spp. (apple, crabapple), Prunus spp. (cherry) including, P. japonica (flowering almond), and P. serotina (black cherry), Rhododendron spp. (rhododendron/azalea) including R. vaseyii (pink shell azalea), Rosa rugosa (rugosa rose), Spiraea spp. (bridal wreath), Syringa spp. (early-mid blooming lilac), S. vulgaris (common lilac), Vaccinium angustifolium (lowbush blueberry), V. corymbosum (highbush blueberry), Viburnum carlesii (Korean spice viburnum), V. x burkwoodii (Burkwood viburnum), V. x burkwoodii 'Mohawk' (Mohawk Burkwood viburnum), Viburnum plicatum var. tomentosum (doublefile viburnum), and Wisteria spp. (wisteria).

Contributing even more color and interest to the landscape are some flowering herbaceous plants and spring ephemerals including: Ajuga reptans (bugleweed), Allium spp. (ornamental flowering onion), Amsonia hubrichtii (Arkansas blue star), Aquilegia canadensis (columbine), A. spp. (columbine), Arisaema triphyllum (Jack-in-the-pulpit), Aurinia saxatilis (basket of gold), Camassia scilloides (wild hyacinth), Cerastium tomentosum (snow in summer), Chrysogonum virginianum (green and gold), Convallaria majalis (lily of the valley), Dianthus deltoides (maiden pinks), Dicentra eximia (fringed bleeding heart), D. spectabilis (old fashioned bleeding heart), D. spectabilis ‘Alba’ (white flowering old fashioned bleeding heart), Dictamnus albus (gas plant), Epimedium versicolor 'Sulphureum' (yellow flowering barrenwort), Gallium odoratum (sweet woodruff), Geranium maculatum (wild geranium), G. macrorrhizum (bigroot geranium), G. sanguinuem (bloody cranesbill), Helleborus niger (Christmas rose), Hyacinthoides hispanica (wood hyacinth), Iberis sempervirens (evergreen candytuft), Iris cristata (crested iris), I. germanica (bearded iris), Lamium maculatum (dead nettle), Linaria annua (money plant), Mertensia virginica (Virginia bluebells), Myosotis sylvatica (forget-me-nots), Nepeta spp. (ornamental catmint), Omphalodes verna (blue-eyed Mary), Papaver orientale (oriental poppy), Phlox stolonifera (creeping phlox), P. subulata (moss phlox), Podophyllum peltatum (Mayapple), Polygonatum commutatum (great Solomon’s seal), P. odoratum 'Variegatum' (variegated Solomon’s seal), Primula spp. (primrose), Stylophorum diphyllum (wood poppy), Tiarella cordifolia (foam flower), Trillium grandiflorum (white flowering trillium), Tulipa spp. (tulip), Veronica umbrosa 'Georgia Blue' (speedwell), Vinca minor (periwinkle), and Viola spp. (violet).

Pests/Problems: Precipitation recorded for this reporting period/week was .04”. The average monthly rainfall for May is 4.04” and as of the 18^th, I have recorded 2.46”. High temperatures recorded this past week were into the 70s and 80s. The heat combined with little to no precipitation makes for a bad combination for plants. Many weeds are in flower including some of the most invasive: Alliaria petiolata (garlic mustard),an herbaceous plantwhich is in full bloom at this time and can easily be spotted because of its white flowers and can be seen growing anywhere and everywhere including on roadsides, and in woodlands, wetlands, and gardens; Elaeagnus umbellata (autumn-olive), a woody invasive shrub/small tree easily detected by its silvery leaves and thorny branches; and Lonicera maackii (Amur honeysuckle), a woody invasive shrub tis easily detected by its delicate white/yellow flowers. Toxicodendron radicans (poison ivy) continues to leaf out and it is indentifiable now with its shiny red leaves of three. Ticks, mosquitoes, and black flies are feeding and active.

Central Region (Boylston)

General Conditions: As lovely as it was to have some good precipitation and seasonable if not cooler temperatures just a few short weeks ago, it’s certainly welcome to have a stretch of warmer than average temperatures at this point in the season. Evening lows are still dipping down into the 40’s, making for generally nice sleeping weather and enjoying having the windows open. Unfortunately, we’re now teetering back into drought conditions like we experienced at the start of the spring season this year, with barely any measurable precipitation during the reporting period. Spring bulbs are largely done at this point, but many of our native species are coming into bloom or at their peak. It will be dogwood season for quite some time. Our native flowering dogwood, Cornus (or Benthamidia) florida, is just coming into bloom. This beautiful tree is native to the eastern United States and bears long lasting flowers in mid-spring. The showier part of the flower is actually a bract (modified leaf) rather than a flower petal, and as a result, the “flowers” last longer when compared to other spring flowering trees like magnolias and crabapples. Flowering dogwood is susceptible to dogwood anthracnose, which can severely impact a tree’s health.

Pests/Problems: At this point, most pests and problems are weather related or harmful to people rather than plants. Poison ivy is actively growing, and quite visible this time of year thanks to reddish new foliage. Mosquitoes and ticks remain active. The lack of precipitation is again concerning, especially for newly planted landscapes.

Pioneer Valley Region (Amherst)

General Conditions: The landscape is luxurious with new growth in the Pioneer Valley as we pass the mid-month marker for May 2021. The transformation from a stark and barren landscape in January is nearly complete and this period of late spring is truly stunning. We are now one month from the summer solstice as daylight continues to increase. This is a good time to determine exactly how many hours of sun certain plants receive, as it’s a useful metric when assessing overall health. Many deciduous hardwoods are at or near full leaf-out, such as beech, oak and maple. Precipitation was limited this past week, with scattered thunderstorms that tracked from north to south occurring on 5/16 and 5/17. While some areas experienced brief but heavy downpours, the distribution was very patchy. Conditions warmed dramatically over this past week, with high temperatures reaching the upper 70s (5/14–5/17) and 80s (5/18 & 5/19). Low temperatures in the 30s appear to be behind us until autumn. The long-term forecast calls for more unseasonably warm temperatures in the upper 80s. Average high temperatures in mid- to late May hover from the upper 60s to low 70s, so this is a major departure. Young and tender new growth will be susceptible to wilt and these plants should be monitored closely until new growth hardens off. While many cities and towns across the Commonwealth have water use restrictions (see most current map here), only one member of the tri-counties is currently listed (Northampton). The most recent update from the U.S. Drought Monitor shows drought classifications have been lifted from all of western Mass, which is an encouraging development after the dry conditions in early spring. Due to the recent warming, soil temperatures made a big leap over last week’s figures, with full sun temperatures now well above 60°F. Overall, the winds have mostly diminished throughout the area and this is welcome. That said, on Tuesday, 5/18 there were strong afternoon gusts and the dispersal of silver/red maple samaras and elm seed was impressive. Huge volumes of papery elm seeds were blowing across the UMass campus. While warming temperatures are drying the upper soil layer, the drying is greatly accelerated during windy days. Pollen levels continue to remain very high and we have not yet experienced what eastern white pine has in store for this season. Turf grasses are growing rapidly right now and many lawns are green and vibrant. Mosquitoes are now very active in forests and open settings at dusk.

Pests/Problems: After the summer drought of 2020, consider supplemental irrigation for trees that may have suffered. These trees may only require intermittent watering during the growing season, such as once or twice a month. Given the increasing temperatures and recent history of short-term droughts (2016 and 2020), there’s a need to reconsider when and if some trees can be left on their own and still be expected to thrive. Maple anthracnose has been reported and observed on both sugar maple and Japanese maple. Many mature Japanese maples on the UMass campus have varying levels of stem cankering infections. These pathogens can quickly spread when trees are drought-stressed. The diffuse, brown-colored foliar lesions of apple scab are visible on landscape crabapple, especially on heavily shaded trees. Trees and shrubs that were recently planted may suffer from transplant shock this season, exhibiting delayed and stunted growth. While this is very concerning, if the leaf/needle color appears normal, the plant should recover. However, it’s critical that plants suffering from shock receive regular and thorough watering for the duration of the growing season. As discussed previously, hemlock woolly adelgid (Adelges tsugae) populations are high this season. A single treatment of dinotefuran (state restricted use), as a basal bark application from the root flare to chest height, can provide multi-year control of both the adelgid and the elongate hemlock scale (Fiorinia externa). This will eliminate the need for aerial spraying of broad-spectrum insecticides like bifenthrin. Horticultural oil can also be effective in controlling this invasive pest. The new lime green growth present now on eastern hemlock contrasts beautifully with the older, dark green needles. Once again, we’re reminded that hemlock is a supreme landscape tree worthy of our time and energy. It occupies a niche that few conifers inhabit, performing well in shaded settings. The dark green color also provides an excellent backdrop for a variety of perennials. With more than 200 unique cultivars listed in the Encyclopedia of Conifers, there’s an eastern hemlock for every landscape.

Berkshire Region (Great Barrington)

General Conditions: During the past week, it felt as if we’ve gone from March to July, weather wise. Daytime highs went from the upper 40s to 80˚F, while night time lows went from the low 30s at the start of the latest reporting period to 50s at the end of the period. Pittsfield recorded low temperatures of 34˚F on 5/13 and 35˚F on the morning of 5/14. Elsewhere, North Adams had lows of 35˚F on both the 13^th and 14^th; Richmond recorded lows of 34˚F on the 13^th and 35˚F on the 14^th. While none of these recorded temperatures were below the freezing mark of 32˚F, frost was wide spread in the County on both of those days. Frost on plants at ground level, e.g. grass, can occur despite air temperatures above freezing. This is not an unusual occurrence on clear, calm nights. On such nights, cool, dense air sinks to ground level. That’s one reason why frost may occur in low-lying areas but not at even slightly higher ground. Also, evaporation of moisture from near ground surfaces can lower temperature at that level. With U.S. Weather Service thermometers typically placed at a height 6 feet, a freezing temperature at ground level could be missed. Nevertheless, no damage to plants from the light frost was observed. That may not be the case where seedlings of tender annuals may have already been planted. Besides the temperature shift, the period was also a dry one, in contrast to the previous week. Little or no rain was recorded anywhere in the County. Though the top inch of soil is dry, soil just below that retains some moisture. Noticeably, plants which were seeded and seemed reluctant to germinate suddenly appeared this week in response to warming air and soil temperatures. Turfgrass continues to grow rapidly and one must hustle to keep up with mowing, especially if the 1/3 rule is followed, that is, never taking off more than 1/3 the height of grass blades. Natural and managed landscapes remain colorful with the many flowering trees and shrubs.

Pests/Problems: Warming temperatures have spurred an increase in the weed population. Poison ivy has emerged over the past week and it behooves landscape workers to be aware of that when tending to home grounds. Among the insect pests observed were Forest tent caterpillars on beech, birch, and crabapples, imported willow leaf beetle (adults) on foliage of willow species, boxwood psyllids and boxwood leaf miners (larval and pupal stages), hydrangea leaftier on hydrangea, and aphids on several plant species. Spruce spider mites remain active. Voles continue their tunneling activities in landscapes while chipmunks have been observed digging in tilled soil where seedlings were recently transplanted, thus upending the seedlings. Squirrels have been nipping off the tips of branches on certain trees though this pruning activity does not seem to have any negative affect on the trees. The deer tick population remains very high and all the usual precautions must be adhered to in order to avoid the severe diseases transmitted by this pest. In addition to ticks, black flies, mosquitoes, wasps, and carpenter bees are plentiful. Few plant diseases have thus far been observed with the exception of apple scab and cedar-apple rust.

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 numerous reports of arborvitae decline and death across the state this spring. With the sheer number of arborvitae in the landscape, it’s understandable that some would be suffering after last season’s drought. As a workhorse for property screening and boundary establishment, arborvitaes serve an important role in the landscape. Deep planting, circling/girdling roots, poor root form, competition with turf grasses and drought stress may have contributed to increased susceptibility to cold injury during the winter months. While the UMass Plant Diagnostic Lab receives many arborvitae samples each year, submissions at this time are higher than usual. Two needle blight pathogens are particularly common on arborvitae, mentioned below in example cases. In nearly all cases, these fungi require some type of predisposing stress to cause serious disease. These fungal pathogens often co-occur on symptomatic arborvitae but pathogenicity trials that would examine their ability to cause disease in a controlled setting are lacking.
• Scattered branch dieback and death of various arborvitae (Thuja occidentalis 'Smaragd’, T. plicata and T. standishii × plicata 'Green Giant'). In one case, the dieback was due to transplant shock, winter injury and Phyllosticta needle blight. In October of 2020, 15 trees were planted as a border screen. The neighboring property has an existing border hedge composed of a tall, deciduous shrub. As such, the trees receive a mixture of sun and shade. In early March, symptoms of branch dieback appeared as pale green to brown-colored needles on scattered shoots. Submitted shoots were desiccated and some may have been damaged during the process of transplanting, which can be difficult to avoid. Drought stress prior to transplanting may also have been a factor which would have interfered with natural cold acclimation. The fungal pathogen Phyllosticta thujae was abundant on incubated needles but typically requires predisposing stresses to establish and spread. Dieback of the Green Giant arborvitae was also likely related to transplant shock. The trees are nine-years-old and were transplanted in fall of 2020. They receive six hours of sun per day with supplemental water provided by drip irrigation. Also, in March, branch tip dieback developed which has uniformly progressed inward on the branches. In this case, Pestalotiopsis was isolated from the blighted needles.
• Dieback of red oak (Quercus rubra) due to stem/branch cankering (Coryneum) and anthracnose (Colletotrichum). The tree is roughly five- to ten-years-old and was planted in early fall of 2020 at the corner of a residential property. The tree receives a mixture of sun and shade with drip irrigation. The submitted stems, approximately 0.5” in diameter, had large, black-colored cankers that had split open. These were the result of infection by the cankering pathogen Coryneum, which has been more abundant recently due to the high number of stressed oaks. The current season’s shoots and leaves had black lesions and distorted foliage due to the anthracnose pathogen Colletotrichum. While not as common on oaks, Colletotrichum has an enormous host range among forest and landscape trees and shrubs.
• Foliar blight of rhododendron (Rhododendron sp.) caused by Phyllosticta, Phomopsis and Colletotrichum. Mature plant, approximately 15-years-old, has been present at the property for 12 years. The shrub resides in a south-facing bed that is mulched and rich with organic matter. Over last fall and winter, marginal leaf blight and spots/blotches developed on the foliage. The symptoms were present in prior years and appeared to worsen after pruning in 2020. All three pathogens are opportunistic on rhododendron and can readily spread on plant parts injured by cold injury. Root sampling, while limited, suggested the roots were healthy.

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

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 adults are active, as they typically are from October through May, and “quest” or search for hosts at any point when daytime temperatures are above freezing. Engorged females survive the winter and will lay 1,500+ eggs in the forest leaf litter beginning around Memorial Day (late May). 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, 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 .

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 .

• Winter Moth: (Operophtera brumata) data since 2017 has indicated that the winter moth population in eastern Massachusetts has been on the decline while the percent of winter moth pupae parasitized by Cyzenis albicans has increased! This is excellent news, as it is data supporting the evidence that winter moth populations have decreased while the parasitic fly, C. albicans, has become established at many locations in New England. Dr. Joseph Elkinton’s laboratory at UMass Amherst has released this biological control of winter moth since 2005 and conducted the rigorous sampling required to determine where the insect has established and what its impact on the winter moth population has been at multiple sites in eastern MA. More information about the Elkinton Lab’s research and the biological control of winter moth can be found here: https://www.fs.fed.us/foresthealth/technology/pdfs/FHAAST-2018-03_Biology_Control_Winter-Moth.pdf

The take-home point? Do not worry about winter moth this year! In fact, management of this insect in landscaped settings will likely not be necessary in most locations. In recent years, it is worth-while to note that some areas on the Cape and other locations in eastern MA have reported noticeable cankerworm populations in the spring, which are often confused for winter moth. Read more about cankerworms below.

For blueberry growers in eastern Massachusetts concerned about winter moth, please visit this update from Heather Faubert, University of Rhode Island: https://web.uri.edu/ipm/2021/04/april-22-winter-moth-update/

• 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:

• 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 overwintering 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.
• 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.
• 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, base 50°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

• 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.
• 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 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

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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Diagnostic Services

UMass Laboratory Diagnoses Landscape and Turf Problems - The UMass Extension Plant Diagnostic Lab is available to serve commercial landscape contractors, turf managers, arborists, nurseries and other green industry professionals. It provides woody plant and turf disease analysis, woody plant and turf insect identification, turfgrass identification, weed identification, and offers a report of pest management strategies that are research based, economically sound and environmentally appropriate for the situation. Accurate diagnosis for a turf or landscape problem can often eliminate or reduce the need for pesticide use. For sampling procedures, detailed submission instructions and a list of fees, see Plant Diagnostic Laboratory

Soil and Plant Nutrient Testing - The University of Massachusetts Soil and Plant Nutrient Testing Laboratory is located on the campus of The University of Massachusetts at Amherst. Testing services are available to all. The lab provides test results and recommendations that lead to the wise and economical use of soils and soil amendments. For more information, visit the UMass Soil and Plant Nutrient Testing Laboratory web site. Routine soil analysis and particle size analysis ONLY (no other types of soil analyses available at this time). Turnaround time: Please plan for the fact that date of receipt in the lab is affected by weekends, holidays, shipping time, and time for UMass Campus Mail to deliver samples to the lab. Campus Mail delivery only takes place on Monday, Wednesday, and Friday due to pandemic restrictions.

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