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Landscape Message: August 12, 2016

August 12, 2016
Issue: 
18

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 bi-weekly July through September. The next message will be available on August 25. To receive immediate notification when the next Landscape Message update is posted, be sure to join our e-mail list.

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


Scouting Information by Region

Environmental Data

The following growing-degree-day (GDD) and precipitation data was collected for an approximately two week period, July 28 through August 10. Soil temperatures and phenological indicators were observed on or about August 10. Total accumulated growing degree days (GDD) represent the heating units above a 50° F baseline temperature collected via our instruments for the 2016 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.

Region/Location

GDD

Soil Temp
(°F at 4" depth)

Precipitation
(2-Week Gain)

Time/Date of Readings

2-Week Gain

2016 Total

Sun

Shade

Cape Cod

312

1700

85

80

0.93

4:40 PM 8/10

Southeast

285

1,625

75

71

0.90

5:45 PM 8/10

North Shore

324

1691

69

65

0.31

9:45 AM 8/10

East

346.5

1897.5

74

70

0.37

4:00 PM 8/10

Metro West

315.5

1760.5

71

67

0.42

5:45 AM 8/10

Central

302

1820

72

68

1.61

4:11 PM 8/10

Pioneer Valley

321

1860

74

72

2.58

4:00 PM 8/10

Berkshires

237

1583

77

70

1.34

12:30 PM 8/10

AVERAGE

305

1742

75

70

1.06

-

n/a = information not available

Drought Conditions Update: Nearly 100% of Massachusetts is currently under drought status, of that 92% of the Commonwealth is classified as at least 'Moderate Drought', 62% is classified as 'Severe Drought', and nearly 4% is classified as 'Extreme Drought' (a large portion of Middlesex County and a small portion of western Essex County.  For more information see http://droughtmonitor.unl.edu/Home/StateDroughtMonitor.aspx?MA

Phenology

Phenological indicators are a visual tool for correlating plant development with pest development. The following are indicator plants and the stages of bloom observed for this period:

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.
Clethra alnifolia (Summersweet Clethra) Begin/Full Full Full Full Full Full Full Full
Hibiscus syriacus (Rose-of-Sharon) Full Full Full Full Full/End Full Full Full
Buddleia davidii (Butterfly Bush) Full Full Full/End Full/End Full/End Full Full/End Full
* = no activity to report/information not available

Regional Notes

Cape Cod Region (Barnstable)

General Conditions: The weather for this reporting period has been typical late of July/early August. Warm and humid days have been the norm, with some of the nights starting to cool off into the low 60s F. Rainfall has been spotty at best. Marstons Mills recorded 0.39” on July 29, 0.43” on August 1, and then nothing until 0.12” was recorded on August 10. Soils are extremely dry and the Cape is now classified as being in a moderate drought. Vitex is in full bloom, along with Panicle Hydrangea. In the perennial garden, Hardy Hibiscus is blooming.

Pests/Problems: The continued lack of adequate rainfall combined with high soil temperatures is the most serious problem in Cape landscapes. Soils are extremely dry, even after irrigation. Unirrigated lawns are completely brown. Unirrigated landscape plants are beginning to flag. Marginal browning of foliage is showing up on trees and shrubs. Newly planted landscape materials are most at risk.

Pest activity is dropping off. Japanese beetles are still around although their numbers appear to be dropping off. Oriental beetles are active but not present in large numbers. Asiatic garden beetle continues to be active. The hot, dry weather conditions are perfect for outbreaks of spider mites on perennials and annuals. Wasps and bees are very active. Ground nesting bees are active, especially in sunny, dry soils.

Powdery mildew can be observed on susceptible phlox, beebalm, and lilac. Downey mildew is wiping out basil.

Southeast Region (Hanson)

General Conditions: Over the past two weeks, sunny weather with high temperatures mostly in the 80s and some 90s continued to be the norm. Hanson received 0.90 inches of rain, having received 0.65 inches of rain today, Aug. 10th, which dampened the soil slightly. Before the rain today, unirrigated soils were dry and dust-like to a depth beyond 12 inches. This brief rain will take a bit of the stress off plants, but more rain is drastically needed. The following plants are in full bloom: Clerodendron trichotomum, Albizia julibrissin, Campsis radicans, Aesculus parviflora, Clethra alnifolia, Hydrangea paniculata, Hydrangea macrophylla, Hydrangea quercifolia (Oakleaf Hydrangea), Hydrangea arborescens (Smooth Hydrangea), roses, Rose-of-Sharon, Echinops ritro (Globe Thistle), Rubus odoratus, Lobeliasiphilitica, Phlox paniculata (Garden Phlox), Echinacea sp., perennial Hibiscus, Hosta plantaginea and other late blooming hosta, Persicaria polymorpha, Lythrum salicaria, Liatris spicata, Lysimachia clethroides, Perovskia atriplicifolia, daylilies, Shasta daisy, Nepeta sp., Joe-pye-weed, Heliopsis ‘Summer Sun’, Helianthus sp., Hollyhocks, Monarda didyma (Beebalm), Silphium sp., Actaea racemosa, Veronicastrum virginicum, Rudbeckia triloba, Rudbeckia fulgida, Rudbeckia ‘Herbstonne’, Coreopsis sp., Astrantia major and Campanula sp. Unfortunately, the heat and drought have pushed many plants to reduce or end bloom early.

Pests/Problems: The biggest landscape problem right now is probably the drought. Most areas in MA are in a severe to moderate drought watch. In unirrigated landscapes, lawns are brown; some trees are dropping leaves or displaying “premature fall color”, marginal foliar browning is occurring on many plants, etc. When daylilies and hosta start to wilt, collapse and turn brown, then we know it is really dry. When plants reach their permanent wilting point, they sometimes will not recover. The constant reminder this season continues to be: urge clients to water drought-stressed plants, especially those of high value and those defoliated by gypsy moth caterpillars this season. Unfortunately, many towns are on partial or total water bans. Many of the oak trees defoliated by the caterpillars have yet to put out that second flush of significant foliage. It is a challenging season for growing and maintaining plants. .

The drought has, so far, reduced the mosquito population. This could change if we get rain. Although the mosquito numbers are down, do not let down your guard down and still continue to use repellents like DEET. As mentioned in the last message, a mosquito tested positive for EEE (Eastern Equine Encephalitis) in Middleborough, MA and according to reports, West Nile Virus (WNV) can flourish in dry conditions. Supposedly, as natural water supplies dry up, some species of mosquitoes that carry WNV, find breeding sites in other areas of standing water: bird baths, pools, plant saucers, etc. The take home message is to have clients empty and change containers of water frequently or use Bacillus thuringiensis israelensis.

As many people know, there are many tick borne diseases (http://www.cdc.gov/ticks/diseases/index.html), and deer ticks are vectors for several of those diseases, including Lyme disease. For everyone working in or enjoying the outdoors, it is important to be able to recognize the symptoms of Lyme disease. Here is a link from the Center for Disease Control (CDC):

http://www.cdc.gov/lyme/signs_symptoms/. Recently, a friend who works outdoors reported that she had Babesiosis (http://www.cdc.gov/parasites/babesiosis/,

http://www.cdc.gov/parasites/babesiosis/disease.html).

Japanese beetles remain active but appear to be few in number. Asiatic Garden beetles and Oriental beetles also appear few in number. Peak emergence of Asian Longhorned Beetle (ALB) is usually in August and this insect attacks healthy trees. Monitor susceptible trees like maples, horsechestnut, elm, poplar, willow, etc. (For more information, see Tawny Simisky’s Insect section of the Landscape Message.)

Continue to monitor for the following insects and manage if needed: viburnum leaf beetle; spider mites; redheaded pine sawfly; introduced pine sawfly; Andromeda, rhododendron and azalea lacebugs; aphids; snail; slugs and leafhoppers. Remember to be cautious when applying pesticides in hot weather and always read the label.

Damage to flowers of Echinacea, Rudbeckia, marigolds, Helianthus, Bidens, Heliopsis, and other plants in the composite (Asteraceae) family, from the sunflower moth caterpillar is really beginning to show up, with the center cone of the flowers turning a black-brown and looking messy from all the frass.

Monitor dogwoods for dogwood sawfly.

Rabbits, deer and chipmunks continue to browse.

North Shore Region (Beverly)

General Conditions: This reporting period was hot and dry. Only 0.31 inches of rain was recorded at Long Hill during this period. However some rain is expected today (Wednesday 8/10). Day temperatures ranged from the high 70s to the high 80s during this period. Temperature above 90 degrees was recorded only on one day, July 28, with the high temperature rising to 94 degrees. Long Hill gained 324 growing degree days (GDD) during the last two weeks. Woody plants seen in bloom include: Sourwood (Oxydendrum arboreum), Silk tree or Mimosa (Albizia julibrissin), Oakleaf hydrangea (Hydrangea quercifolia), Butterfly bush (Buddleia davidii), Rose-of-Sharon (Hibiscus syriacus), Harlequin glorybower (Clerodendrum trichotomum), and Summersweet Clethra (Clethra alnifolia). Herbaceous plants seen in bloom include: Culver’s root (Veronicastrum virginicum), Balloon flower (Platycodon grandiflorus), False anemone (Anemonopsis macrophylla), Cardinal flower (Lobelia cardinalis), Fairy candles plant (Actaea racemosa), Turk's cap lily (Lilium superbum), Bee balm (Monarda didyma), Shasta daisy (Leucanthemum x superbum), Garden phlox (Phlox paniculata), hostas (Hosta spp.), sedums (Sedum spp.), Astilbe (Astilbe spp.), Summer flowering roses (Rosa sp.), Clematis vines (Clematis paniculata), Spiderwort (Tradescantia sp.), late blooming bellflower (Campanula persicifolia), Persicaria (Persicaria polymorpha), Heucheras (Heuchera sp.) and Water lily (Nymphaea odorata).

Pests/Problems: The area is in a severe drought and some plants, especially shrubs and non-irrigated perennials, are showing signs of drought stress such as wilting. Non-irrigated turf is completely brown. Diseases observed include cedar quince rust (Gymnosporangium clavipes) on hawthorne, Cedar apple rust (Gymnosporangium juniperi-virginianae) on crabapples. Also observed was Powdery mildew on Lilac and phlox. Japanese beetles were also observed causing problems on some plants. Watch for poison ivy as you walk or work in the woods. Remember also that ticks and mosquitoes are still very active. Protect yourself with insect repellent.

East Region (Boston)

General Conditions: Hot and dry conditions have persisted over the past two weeks. We began this reporting cycle with temperatures in the 90's before a cold front moved in, dropping temperatures to the low 80's and three days of conditions in the mid-70's. Hot and humid conditions returned for the final six days as temperatures warmed to the high 80's and low 90's. Highs ranged from 74° F to 93° F averaging 85.5° F. We have received only 0.27” of precipitation, from 3 events, the largest on the 2nd dropped 0.16", and a fast moving thunderstorm on the 6th brought 0.03". Despite the conditions, several plants continue to bloom: Clerodendrum trichotomum (Harlequin glorybower), Campsis radicans cultivars (trumpet vine), Hibiscus syriacus (Rose of Sharon), Hibiscus moscheutos ssp. palustris (swamp rose mallow) and Rosa sp. hybrids (rose). Many herbaceous, pollinator friendly plants continue to flower including many species of Asclepias sp. (milkweed), Helianthus tuberosus (Jerusalem artichoke), and Silphium perfoliatum (cup plant).

Pests/Problems: Lack of soil moisture is the topic of the day! The East region last received significant precipitation on June 30th and prior to that, on May 12th. We are experiencing a significant deficit in rainfall. Early leaf drop is occurring: Amelanchier sp. (shadbush), Betula sp. (birch), Cercidiphyllum japonicum (katsura), Magnolia sp. (magnolia), legumes and many others. Non-irrigated turf has gone dormant. Crabgrass continues to thrive in every available opening. Purple loosestrife (Lythrum salicaria) is in full flower and thriving.

Metro West (Acton)

General Conditions: Once again, we just experienced another recording period without any significant precipitation. The average monthly precipitation for June is 3.93” and recorded for the month was 1.63”, for July the monthly average is 4.07” and recorded was 1” and lastly for August, the monthly average is 3.72” and the total recorded so far is 0.23”. The metro west area is near 8” below its average annual precipitation and it is apparent with the brown lawns, and dying, dropping and flagging foliage on trees, shrubs and perennials. Also during this two-week period, there were a total of five days where the high temperature was recorded in the 90s. The high temp of 96° was recorded on the 27th. Woody plants seen in bloom this past week are: Albizia julibrissin (Silk Tree), Buddleia spp. (Butterfly Bush), Clethera alnifolia (Summersweet), Hibiscus syriacus (Rose-of-Sharon), Hydrangea paniculata (Panicle Hydrangea), and its many cultivars including 'Tardiva', Oxydendron arboreum (Sourwood), Rosa rugosa (Rugosa Rose), R. 'Knockout' (The Knockout family of Roses), and Rosa spp. (Rose). Woody vines in bloom are Campsis radicans (Trumpet vine) and Clematis spp. (Clematis). Contributing even more color and interest to the landscape are some flowering herbaceous plants including: Astilbe spp. (False spirea), Boltonia asteroids (Bolton’s Aster), Cichorium intybus (Chicory), Daucus carota (Queen Anne's Lace), Echinacea purpurea (Coneflower), Echinops ritro (Globe Thistle), Hemerocallis spp. (Daylily), Hosta spp. (Plantain Lily), Lavendula angustifolia (Lavender), Liatris spicata (Spike Gayfeather), Limonium latifolium (Sea Lavender), Lysimachia clethroides (Gooseneck Loosestrife), Macleaya microcarpa (Plume Poppy), Monarda didyma (Bee-Balm), Patrinia gibbosa (Patrinia), Perovskia atriplicifolia (Russian Sage), Phlox carolina (Carolina Phlox), P. paniculata (Garden Phlox), Rudbeckia fulgida var. sullivantii 'Goldsturm' (Black-eyed Susan), Senna marilandica (Wild Senna), and Solidago spp. (Goldenrod).

Pests/Problems: The lack of any rain continues to be a grave concern for our trees and shrubs in the landscape. A severe drought watch for this area and for most of the central and northeastern regions in the State has been declared by the National Drought Mitigation Center. Signs of plant stress are apparent in the landscape including premature leaf drop, early fall color and wilting. Powdery mildew is evident on Monarda (Bee Balm), Phlox and Syringa (Lilac). One of our most aggressive weeds, Cynachum nigrum (Black Swallowwort) is setting seed. Already setting seed and quite visible is Ailanthus altissima (Tree of Heaven). Look for it growing along roadsides and in medians. Emergence season is upon us for the Asian Longhorned beetle so continue to check your trees for oviposition sites, frass, exit holes and the beetle. Most importantly, begin to scout for the Asian Longhorned beetle! Monitor the 12 host genera: Acer (Maple), Betula (Birch), Ulmus (Elm), Salix (Willow), Aesculus (Horsechestnut), Fraxinus (Ash), Platanus (Plane Tree), Populus (Poplar), Sorbus (Mountain Ash), Albizia (Mimosa), Cercidiphyllum (Katsura) and Keolreuteria (Golden Raintree) for this invasive pest.

Central Region (Boylston)

General Conditions: Hot and dry conditions predominated but a few moderate days, and a few rain episodes have punctuated this period. The most significant rain fell on the evening of July 27th when a deluge moved quickly through dropping nearly ¾” in a under an hour. The rainfall during this period has brought unirrigated turf out of dormancy but done little to relieve the stress to unirrigated trees and shrubs. Patches of scorched trees along roadsides can be seen throughout the region. In addition to the indicator plants in bloom the gardens are abundant with annuals and vegetables. Perennial Geranium (Geranium ‘Rozanne’), Summer Phlox (Phlox paniculata), Rose of Sharon (Hibiscus syriacus), Clethra barbinervis, Vitex rotundifolia, Anemonopsis macrophylla, Russian Sage (Perovskia atriplicifolia), Joe Pye Weed (Eupatorium cvs.), Black-Eyed Susan (Rudbeckia 'Goldsturm'), Rudbeckia 'Henry Eilers', Hydrangea paniculata cultivars are also lighting up the gardens.

Pests/Problems: Drought stress is still our number one concern. Though we have had some relief during the past two weeks, the 1.61" of rain that fell came in scattered storms or gully washing downpours that ran off rapidly. We remain well below expected rainfall for this time of year. Many communities have watering bans and/or restrictions and water levels in local streams, lakes and ponds are visibly low. Strikes from fireblight are still showing up on Malus and related rose relatives; blister beetle damage is slowing down; Dogwood Sawfly is still active; and abundant leafhopper and whitefly activity was seen this period on Wafer-ash (Ptelea trifoliata).

Pioneer Valley Region (Amherst)

General Conditions: Conditions this past reporting period were much wetter in the Pioneer Valley compared to the rest of the summer to date. Many towns along the Connecticut River received over 2.5ʺ of rainfall, with portions of central Hampshire County receiving over 3.25ʺ (Easthampton). The two biggest rain events took place overnight on 7/30 - 7/31 and on 8/2, a stretch when high temperatures plummeted into the 70s. These were soaking rainstorms that helped to replenish shallow-rooted perennials and turfgrasses. They were not enough, unfortunately, to thoroughly wet the soil to a depth that would significantly benefit most trees and shrubs. Additional small (<0.25ʺ) storms have passed through since, scattered throughout the tri-county region. Temperatures were a bit cooler through much of this reporting period compared with most of July, with highs in the 80s and lows dipping into the 50s at times. As we enter the weekend a heat advisory has been issued with forecasted temperatures in the 90s accompanied by extremely high humidity. Heat index values are expected to soar over 100°F as dew points settle into the lower 70s. Scattered thunderstorms are also expected so hopefully additional rains will develop throughout the region.

Pests/Problems: Turfgrasses appear to be responding to the rain with renewed growth, especially in shaded settings away from the blazing heat of the sun. Unfortunately, crabgrass and other lawn weeds are now growing strong as well. The rain was likely too little, too late for many drought-stressed trees and shrubs on the landscape. Numerous plants have wilted leaves, scorched leaf margins, or foliage that is browning and prematurely shedding. A mature katsura tree on the UMass campus has been shedding a significant number of green leaves in recent weeks. The upper canopy it almost totally barren at this point. Dutch elm disease is rampant in the landscape, due in part to the drought conditions. The usual assemblage of foliar blight and anthracnose fungi can now be found along with blighted stems from opportunistic cankering fungi. Additional trunk rot fungi are also starting to appear for the season, such as the northern tooth fungus (Climacodon septentrionalis) on sugar maple. The recent rains were a boon to mosquitoes, which are now abundant after being scarce for weeks this summer.

Berkshire Region (Great Barrington)

General Conditions: The rain of the past two weeks helped a little but had no effect on plants severely stressed by the summer-long drought. Dieback on several otherwise healthy trees and shrubs is not uncommon. Some herbaceous perennials have also suffered as witnessed by yellowing of foliage and or leaf drop. This is a good time to evaluate the drought tolerance of herbaceous perennials. Among the plants which are least affected are yarrow (Achillea species), lamb’s-ears (Stachys byzantine), mugwort or wormwood (Artemisia species), Russian sage (Perovskia atriplicifolia), catmint (Nepeta x faassenii), lavender (Lavandula), and creeping snow-in-summer (Cerastium tomentosum). You will have noticed that they all have something in common: their foliage is silver or gray. The gray and silver color is due to reflection of sunlight off tiny hairs on the leaves. This reflection of solar radiation has the effect of cooling the leaves which in turn reduces evapotranspiration (evaporation of moisture from the leaves). If in drought..uh, doubt, recommend inclusion of silver or gray foliage plants in flower gardens subject to drought stress.

Pests/Problems: The rain did perk up some lawns which showed considerable browning from drought stress. However, brown spots are still quite common, especially on lawns mowed low, areas subject to heavy foot traffic and soil compaction.

Leaf spots are the most common disease of ornamental plants and are particularly visible now as the spots have expanded in size. Powdery mildew has also gotten worse on the usual hosts, i.e. lilacs, beebalm, ninebark (Physocarpus), and on Joe Pye weed (Eutrochium purpureum).

All stages, i.e. adult, nymph, and egg, of oak lace bug were seen on bur oak (Quercus macrocarpa). Crawlers of euonymus scale are active, though some have settled. Imported willow leaf beetle was found in the pupal stage on foliage of willow. Asiatic garden beetle remains active. A few adults of Japanese beetle are still around but few in number.

Wasps, yellow jackets, and hornets are numerous, but one wasp that elicits a lot of fear, unjustly so, is the eastern cicada-killer wasp. One of the largest wasps, it rarely stings anyone other than its prey – cicadas – unless it is man-handled. Killer wasps are solitary wasps and burrow in the ground, often near walks and patios. The ones I saw had burrowed between stepping stones. The large exit holes usually have a deposit of loose soil around them, the result of burrow excavation.

Regional Scouting Credits

  • CAPE COD REGION - Roberta Clark, UMass Extension Horticulturist for Barnstable County - Retired, reporting from Barnstable.
  • SOUTHEAST REGION - Deborah Swanson, UMass Extension Horticulturist for Plymouth County - Retired, reporting from Hanson.
  • 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 Arnold Arboretum, Jamaica Plain.
  • METRO WEST REGION – Julie Coop, Forester, Massachusetts Department of Conservation & Recreation, reporting from Acton.
  • CENTRAL REGION  -  Joann Vieira, Superintendent of Horticulture, reporting from the Tower Hill Botanic Garden, Boylston.
  • PIONEER VALLEY REGION - Nick Brazee, Plant Pathologist, UMass Extension Plant Diagnostic Lab, reporting from UMass Amherst.
  • BERKSHIRE REGION - Ron Kujawski, Horticultural Consultant, reporting from Great Barrington.

Woody Ornamentals

Diseases

Recent pathogens of interest seen in the UMass Extension Plant Diagnostic Lab:

Suspected winter injury and drought stress leading to branch dieback of ornamental cherry (Prunus spp.). Numerous samples of ornamental cherry have been submitted during the 2016 season. In most cases, the trees appeared healthy after budbreak but as the summer progressed, leaves wilted and browned on scattered branches in the canopy. Some of the submitted branch material has harbored stem cankering fungi (e.g. Phomopsis, Botryosphaeria and Cytospora). But, the majority of submitted material has been free of any pests or pathogens. It is suspected that the warm temperatures in December (temperatures were 8–14°F above-average in 2015) delayed cold acclimation or lead to a partial acclimation. Once winter temperatures were seasonable in January and February, freeze injury occurred. A more likely scenario, however, was that warm temperatures in March resulted in natural deacclimation from winter hardiness which was followed by a deep freeze on April 5 and 6, when low temperatures were in the teens to low twenties across the region. Sapwood freezing in the trunk and branches may have resulted from these unseasonably cold temperatures. While the sapwood was injured it was not killed outright and the trees were able to flush new growth in the spring. But, as drought and the heat of summer exacerbated the injury, the trees were unable to move sufficient water to the canopy and branch dieback developed. Dead branches should be pruned immediately to avoid colonization by opportunistic fungal pathogens and insects. Supplemental watering and fertilization should help the trees to recover.

Needle blight, caused by Cryptocline taxicola, and edema (overwatering) on yew (Taxus sp.). Numerous plants in a 100′ long hedge are not thriving. Needles are stunted and pale green to yellow with raised callus tissue on the needle surface. Cryptocline can cause considerable injury to Taxus species, one of the few fungal pathogens of concern on this host. But, the primary concern is that the plants are overwatered. Yews, like any other woody ornamental, require supplemental water when first transplanted. However, once established, yews are very drought resistant and often require no irrigation unless the site has excessively drained soils and high wind exposure.

Dutch elm disease (DED), caused by Ophiostoma novo-ulmi, on American elm (Ulmus americana). Numerous elm samples submitted in recent weeks are positive for DED. Infected trees stressed by drought declined rapidly in July. Elm anthracnose can cause similar symptoms (flagging of upper canopy branches) but has been uncommon due to the drought. Therefore, any observed flagging is likely DED. On a few trees, including a Princeton elm, the leaves did not wilt and yellow first, they simply turned brown and were prematurely shed. Due to the drought, symptom development may be rapid and not consistent with what is commonly observed.

Shoot tip and needle blight, caused by Kabatina, on Siberian cypress (Microbiotia decussata). 10-year-old plant present at the site for five years. Planted on a hillside in full sun with drip irrigation and fertilized in the spring. Submitted needles appeared desiccated and were pale green to brown. Winter injury often predisposes plants to attack from Kabatina.

Stem cankering caused by Cenangium ferruginosum and needle blight caused by Lophodermium seditiosum on Japanese black pine (Pinus thunbergii). Several pines, approximately 40-years-old, have been declining over several years. An infestation of turpentine beetles was discovered on some of the trees as well. Cenangium can often be found attacking hard pines after periods of drought in our region. Lophodermium is not a particularly aggressive needle blight pathogen but can be an important contributor to decline on stressed hard pines. Trees are growing in full sun with lawn irrigation.

Foliar blight and stem cankering, caused by Colletotrichum, coupled with transplant shock of oak (Quercus sp.; red oak group). Twelve trees, 15-years-old, were transplanted at a golf course one year ago. All 12 trees have undersized foliage that is abnormally curled and prematurely shedding from the canopy. No supplemental irrigation has been provided and soil outside of the planting pits is heavy and compacted. Colletotrichum was abundant on the stems and blackened petioles. This dynamic anthracnose fungus can attack stems, petioles, leaf surface and fruit on numerous landscape and forest plants.

 Powdery mildew of London planetree (Platanus x acerifolia) caused by Erysiphe platani.

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

Insects

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

But first, drought conditions: despite the rain that some of us in Massachusetts are experiencing today, this has been an incredibly dry summer. Cornell’s Northeast Regional Climate Center reports that 27% of the Northeast (as of August 4th) is in a moderate-severe drought. They report that Massachusetts, from June 1 through August 2, has received less than 50% of normal precipitation amounts. Unfortunately, this lack of precipitation has broken records in MA, with some areas seeing less than half of their normal precipitation, as reported by the NRCC. Particularly stressed areas (from the Cornell report) include those surrounding: Amherst, Ashburnham, Belchertown, Hingham, Lawrence, Reading and Worcester. For more information about the drought in Massachusetts and the Northeast, visit: http://www.nrcc.cornell.edu/regional/drought/drought.html.

What does this mean for ornamental trees and shrubs? Some are showing signs of drought stress (wilting, browning, etc.) as discussed in the Regional Reports above. This may also mean that plants dealing with the drought may become more susceptible to certain insect and other pest problems, adding to this already harsh environmental stress. Continue to monitor water-stressed plants and water when needed, if possible. The NRCC reports that to date, 137 towns in Massachusetts are observing voluntary/mandatory water restrictions or bans.

  • Asian Longhorned Beetle, Anoplophora glabripennis, ALB adults continue to be active in Massachusetts in August. In fact, the US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) has called August Tree Check Month, as it is a prime time to find ALB adult beetles and report any insects or signs of infestation. They are asking the public to take 10 minutes and inspect their trees, particularly maple. Look for the insect itself (a shiny black bodied beetle with white spots and long antennae with black and white bands) or 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.

    They ask the public to take the following steps:
     
    • Make note of what you found; take a photo when possible (of suspicious damage, the beetle, etc.)
    • Capture the suspicious insect when possible; place it in a container and freeze it
    • Report your findings

      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 captured an Asian longhorned beetle or have seen damage caused by this insect, such as exit holes, 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.

 

  • Emerald Ash Borer (EAB): Agrilus planipennis readily attacks ash (Fraxinus spp.) including white, green, and black ash and has also been found developing in white fringe tree (Chionanthus virginicus). Adults are active and will be throughout August, depending on local temperatures. For a map of the known locations of emerald ash borer in the state, as well as further information about this insect, please visit: https://ag.umass.edu/fact-sheets/emerald-ash-borer.
  • Gypsy Moth: for a review of the activity of this pest in 2016 and management options for 2017, please visit: https://ag.umass.edu/news/gypsy-moth-now-that-we-have-survived-largest-outbreak-since-1981-whats-next.
  • Andromeda Lacebug: Stephanitis takeyairemains active on Japanese Andromeda and will continue into September. Inspect plants known to have S. takeyai in the past (or exhibiting yellow stippling on the upper leaf surface) and inspect undersides of leaves for this season’s lacebugs. 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.
  • Azalea Lacebug: Stephanitis pyrioidesis active on evergreen azaleas. This insect may be more damaging on plants located in warm, sunny locations. Like andromeda lacebug, this insect will remain active into the fall. Plants in hot, dry, sunny sites may be severely impacted by mid- August. Horticultural oil sprays targeting the undersides of the foliage can be very effective for this pest.
  • Black Vine Weevil: Otiorhynchus sulcatus damage is apparent on rhododendron and taxus, but can also be seen on azalea, mountain laurel, and Euonymus. Adult weevils feed along the leaf/needle margins and create rounded notches. Inspect foliage of these plants for notching as adults are feeding. Burlap laid around the base of plants during the time adults are active, through August, can be inspected weekly for adult weevils which can be killed before egg laying.
  • Hemlock Woolly Adelgid: Adelges tsugae is present on eastern and Carolina hemlock and is in its summer dormant period which will last until approximately mid-October. Dormant nymphs can be treated throughout the summer with a horticultural oil spray at the summer rate, however be careful to follow all label instructions to avoid injury to the plant. Avoid using oils when temperatures are close to or above 90°F and when humidity is high.
  • Redheaded Pine Sawfly: remains active at this time. This caterpillar-like insect is yellow with rows of black spots and a rust-colored head capsule. Clusters of these hymenopterans can be seen feeding on pines and will continue into the autumn months. Inspect needle tips for clusters of larvae. Prune out or destroy with a gloved hand in the case of small infested areas. Spinosad is effective against these larvae, whether younger or older.
  • Two-Spotted Spider Mite: Tetranychus urticae is active and 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 (such as many deciduous species) 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: Adults have been actively feeding and will continue into September. Adult beetles may be targeted with a pyrethroid; however, adult beetles are generally more difficult to manage than the larval stages. Planting species of viburnum that are most resistant to the viburnum leaf beetle can help manage this pest. Resistant varieties include V. bodnantense (dawn viburnum), V. carlesii (Koreanspice viburnum), V. davidii (David viburnum), V. sieboldii (Siebold viburnum), and others. Highly susceptible species of viburnum frequently attacked by this beetle can include V. dentatum (arrowwood viburnums), V. opulus (European cranberrybush viburnum), and V. rafinesquianum (Rafinesque viburnum).

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.

A note about Tick Awareness: deer ticks (Ixodes scapularis), the American dog tick (Dermacentor variabilis), and the lone star tick (Amblyomma americanum) are all found throughout Massachusetts. Each can carry their own complement of diseases. Anyone working in tick habitats (wood-line areas, forested areas, and landscaped areas with ground cover) should check themselves regularly for ticks while practicing preventative measures. Have a tick and need it tested? Visit the web page of the UMass Laboratory of Medical Zoology (www.tickdiseases.org) and click on the red Test a Tick button for more information.

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

Management Practices

Plant of the Week: Clethra alnifolia

Clethra alnifolia is a native deciduous shrub growing 3-8’ tall and 4-6’ wide. The common name of summersweet, speaks of the fragrant flower panicles in July and August. Flower panicles are upright, are white or pink depending on the cultivar, and are very popular with bees and butterflies. The glossy dark green leaves are serrated and oblong turning yellow to golden in the fall. Plants grow will in medium to wet soils in full sun to part shade, tolerating both clay soil and heavy shade. Care needs to be taken to prune root suckers, otherwise the plant will have a suckering, naturalized appearance. Along with different flower colors, cultivars also offer variation in size and leaf characteristics. Clethra alnifolia does not have any serious insect or disease problems.

Clethra alnifolia - Summersweet     Clethra alnifolia - Summersweet     Clethra alnifolia - Summersweet

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

Garden Retailers

Basil Downy Mildew (BDM) has been here for a while - it began showing up in CT and MA around mid-July. Symptoms first appear as yellowing on the top of the foliage, as if the plants are nitrogen or nutrient deficient. The underside of the leaves appear "dirty" due to the growth of sporangia, the distributive form of the fungus. All sweet basil cultivars are susceptible to this disease. While there are no resistant cultivars, the tolerant cultivar ‘Eleanora’ (cross of Thai basil and sweet basil) may delay symptoms a couple of weeks.

For more information about BDM, see the Feb. 2015 Greenhouse Update: http://negreenhouseupdate.info/updates/basil-downy-mildew-0


Additional Resources

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For commercial growers of greenhouse crops and flowers - Check out the New England Greenhouse Update website

For professional turf managers - Check out Turf Management Updates

For home gardeners and garden retailers - Check out home lawn and garden resources. UMass Extension also has a Twitter feed that provides timely, daily gardening tips, sunrise and sunset times to home gardeners, see https://twitter.com/UMassGardenClip

Diagnostic Services

A 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 Diagnostics 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 function of the Soil and Plant Nutrient Testing Laboratory is to provide test results and recommendations that lead to the wise and economical use of soils and soil amendments. For complete information, visit the UMass Soil and Plant Nutrient Testing Laboratory web site.   Alternatively, call the lab at (413) 545-2311.

Ticks are active at this time! Remember to take appropriate precautions when working and playing outdoors, and conduct daily tick checks. UMass tests ticks for the presence of Lyme disease and other disease pathogens. Learn more