UMass Extension Landscape Message #11 - 2011 | UMass Extension Landscape Nursery & Urban Forestry | UMass Amherst

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UMass Extension Landscape Message #11 - 2011 May 13, 2011 Quick Links Scouting Information by Region Scouting Information Regional Notes Regional Notes Cape Cod Cape Cod Region (Barnstable) – General Conditions: Overall, the week has been chilly, windy, and wet as a stalled storm system rotated nasty weather back onto the Cape. Friday and Saturday were nice days, Southeast weather wise, but it has been more like March than May since then. Landscapes are looking soggy. Cool East temperatures have slowed down plant development. Pests/Problems: High winds stripped many emerging Metro West leaves from trees over the past few days. Winter moth caterpillars are feeding but overall the infestation is Central spotty. Reports from Brewster indicate fairly high numbers while observations in Marstons Mills show lowered Pioneer Valley numbers. hemlock wooly adelgid egg masses are noticeable. Treatment for black turpentine beetle should be Berkshire wrapping up. The gelatinous orange galls of cedar-apple rust are becoming visible on eastern red cedar. Environmental Data Slugs and snails are abundant. We have had a good infection period for dogwood anthracnose and apple Phenology scab with the prolonged damp weather. Woody Ornamentals Southeast Region (Hanson) - General Conditions: Hanson received 0.60 inches of rain this past week Landscape Turf and the weather continued to be cool extending the bloom of many spring flowering plants. Halesia sp. (Silverbell), Kwanzan cherry, Crabapples, Lilac, dogwood, Cercis canadensis (Eastern Redbud), Viburnum Archived Messages carlesii (Mayflower Viburnum), Viburnum x burkwoodii ‘Mohawk’, R. schlippenbachii (Royal Azalea), Exochorda (Pearlbush), Spiraea prunifolia (Bridalwreath Spirea), Pieris japonica, Pieris floribunda (Mountain Pieris), Fothergilla major (large fothergilla), Fothergilla gardenii (dwarf Fothergilla), Kerria, Daphne tangutica, Daphne x burkwoodii ‘Carol Mackie’, Iberis sempervirens, Epimedium sp., Trillium sp., Tulips, Narcissus, Convallaria majalis (Lily-of-the-valley), Euphorbia polychroma, Brunnera macrophylla, Phlox subulata, Arisaema sp., H. x hybridus, H. foetidus, Corydalis lutea, Corydalis scouleri, Primula sp., Pulmonaria, Ajuga, bearded Iris, Sweet woodruff, Polygonatum sp. (Solomon’s Seal), Saruma henryi, Lamium, Lunaria annua (honesty or money plant), Hyacinth, Tiarella cordifolia (Foam Flower), Lamium, Dicentra eximia, Mertensia virginica (Virginia bluebells), Violets, and Vinca minor are in full bloom. Flowering Quince and Pieris 'Brouwer's Beauty' are ending bloom. Rhus ‘Tiger Eyes’ and Cotinus coggyria are finally starting to leave out. Chionanthus virginicus, as always, is late to leaf out, looks to someone unfamiliar with it, like a dead shrub in the landscape. Japanese maples and Hosta have leafed out providing nice foliage color. Pests/Problems: As of right now, damage by winter moth caterpillars appears to be down this year, however, it may be too early to tell. Some Norway maples appear to have little damage while a few have foliage resembling Swiss cheese. Some Japanese maples are also showing damage. Winter moth caterpillars were found in second, third and fourth instar, and in some instances, fifth, and all on the same leaf! Winter moth caterpillars were found feeding on the foliage of maples (Norway, sugar, paperbark, red and Japanese), roses, Amelanchier, beech, oaks, birch, crabapples, apples and blueberries. They were also found feeding inside the developing fruit of European beech tree. Wasps and hornets, carpenter bees, honey bees, carpenter ants, mason bees, lily leaf beetle adults, Hemlock woolly adelgid, black flies, mosquitoes, deer and dog ticks are all active. Have not seen many ‘tents’ of Eastern tent caterpillar. Beneficial insects are also active. Barberry, one of the Massachusetts invasive plants is in full bloom. Autumn olive, burning bush and Oriental bittersweet will soon be blooming. If warranted, prune or remove the plants now to reduce potential seed production. Ground ivy, buttercups, veronica, violets, chickweed, wild mustard, and dandelions are in full bloom. Continue to check for deer and dog ticks frequently, especially after yard cleanups or walking through tall grass.

East Region (Boston) – General Conditions: We are experiencing a typical New England spring; we have had precipitation six out of the last seven days, but totaling less than an inch. We had an average high temperature of 64.8 °F, but with the winds, it seems quite cooler. We gained 46.5 GDDs compared to 73 gained during this week in 2010. Despite the weather, spring pushes forward with color in full force. Shrubs in bloom include: Andromeda [A. glaucophylla (downy andromeda) and A. polifolia ‘Blue Ice‘ (bog rosemary)], Berberis sp. (barberry), Cotoneaster apiculatus (cranberry cotoneaster), Daphne cneorum ‘Ruby Glow’ (Rose Daphne), Elaeagnus multiflora (cherry elaeagnus), Exochorda ‘The Bride’ (pearlbush), Fothergilla major (large fothergilla), Ilex rugosa (prostrate holly), Kerria japonica (Japanese kerria), Leucothoe [L.

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axillaris (coast leucothoe), L. fontanesiana (drooping leucothoe) and L. recurva (fetterbush)], Lonicera chrysantha (coralline honeysuckle), Poncirus trifoliata (trifoliate orange), Rhododendron [R. canadense (Rhodora), R. kaempferi (torch azalea) and R. vaseyi (pinkshell azalea)], Rhus aromatica (fragrant sumac), Vaccinium [V. angustifolium (lowbush blueberry) and V. corymbosum (highbush blueberry)], Viburnum [V. bitchiuense (Bitchiu viburnum), V. x burkwoodii (Burkwood viburnum), V. carlesii (Korean spice viburnum), V. lantana (wayfaring tree), V. rhytidophyllum (leatherleaf viburnum), V. x rhytidophylloides (lantanaphyllum viburnum) and V. utile (service viburnum)] and Weigela [W. florida (old fashioned weigela), W. hortensis (gardeners weigela), W. praecox (early weigela) and Weigela subsessilis (weigela)]. Trees in bloom include: Betula nigra (river birch), Caragana franchetiana (Franchet peashrub), Cercis canadensis (Eastern redbud), Quercus sp. (oak) and Sorbus yuana. Convallaria majalis (lily of the valley) and Dicentra sp. (bleeding heart) are flowering throughout the grounds. Vines in flower: Akebia quinata (fiveleaf akebia), Clematis alpina (alpine clematis), Schisandra chinensis (magnolia-vine) and Wisteria sinensis (Chinese Wisteria). Interesting and unusual plants in bloom: Davidia involucrata (Dove Tree), Halesia tetraptera (Carolina silverbell), Orixa japonica (Japanese orixa) and Staphylea trifolia (American bladdernut). Pests/Problems: Weeds continue to flower and some have started (and continue) to seed including an array of winter annuals, Poa annua (annual bluegrass) and Taraxacum sp. (dandelion). Alliaria petiolata (garlic mustard) remains in flower, giving an extended period of time to allow for proper management of the plant. Imported willow leaf beetle (Plagiodera versicolora) adults have begun munching on willows. Winter moth (Operophtera brumata) is abundant throughout the grounds, but particularly on maple (Acer sp.), linden (Tilia sp.), horsechestnut (Aesculus sp.) and oak (Quercus sp.). Azalea sawfly has hatched as these first instar larvae begin to feed. European pine sawfly (Neodiprion sertifer) eggs have been spotted and are almost ready to hatch. Hemlock woolly adelgid (Adelges tsugae) are highly visible in the landscape. Hydrangea leaf tier (Olethreutes ferriferana) continues to hatch, continues to bind leaves for shelter and ultimately continues feeding on the leaves. Berberis thunbergii (Japanese barberry) is in flower.

Metro West (Acton) – General Conditions: We gained 35.5 growing degree days this past week.Trees in bloom include Amelanchier spp. (Shadbush, Serviceberry), Cercis canadensis (Redbud), Halesia spp. (Silverbell), Magnolia x loebneri ‘Leonard Messel’and M. ‘Yellow Lantern’, Malus spp. (Apple, Crabapple), Prunus serrulata ‘Kwanzan’(Kwanzan Cherry), P. serotina (Black Cherry) and Pyrus spp. (Pear). Shrubs in bloom include Chaenomeles speciosa (Common Flowering Quince), Daphne burkwoodii ‘Carol Mackie’ (Carol Mackie daphne), Fothergilla gardenii (Dwarf Fothergilla), F.major (Large Fothergilla), Rhododendron ‘Black Satin’, R. ‘Pink Diamond’, R. schlippenbachii (Royal Azalea), R. vaseyii (Pinkshell Azalea), Spiraea thunbergii (Thunberg Spirea), Vaccinium angustifolium (Lowbush Blueberry)and Viburnum x burkwoodii (Burkwood Viburnum). Perennials and spring ephemerals in bloom include: Arisaema triphyllum (Jack-in-the-Pulpit), Asarum canadense (Canada Wild Ginger), Aurinia saxatilis (Basket of Gold), Bergenia cordifolia (Pig Squeak), Caltha palustris (Marsh Marigold), Chionodoxa luciliae (Glory of the Snow), Claytonia virginica (Virginia Spring Beauty), Crocus spp. (Crocus), Dicentra canadensis (Squirrel Corn), D. cucullaria (Dutchman’s Breeches), D. spectabilis (Old Fashioned Bleeding Heart), Epimedium spp. (Barrenwort), Gallium odorata (Sweet Woodruff), Helleborous niger (Christmas Rose), Hyacinthus sp. (Hyacinth), Iris germanica (Dwarf Bearded Iris), Linaria annua (Money Plant), Mertensia virginica (Virginia Bluebells), Muscari sp. (Grape Hyacinth), Myosotis sylvatica (Forget-me-not), Narcissus spp. (Daffodil), Phlox subulata (Moss Phlox), Primula spp. (Primrose), Stylophorum diphyllum (Wood Poppy), Tiarella cordifolia (Foam Flower), Trillium erectum (Red Flowering Trillium), T. grandiflorum (White Trillium), T. luteum (Yellow Wakerobin), Tulipa sp. (Tulips), Uvularia sessilifolia (Bellflower), Vinca minor (Periwinkle), Viola spp. (Violets) and Waldsteinia ternata (Barren Strawberry). A single vine was seen in bloom this week and that was Aristolochia durior (Dutchman’s Pipe). Pests/Problems: Caterpillars continue to grow and to actively feed on the foliage of Prunus (Cherry) and Malus (Apple, Crabapple).Ticks, mosquitoes and black flies are all feeding and active. Many weeds are in flower including one of the nastiest one of all, Alliaria petiolata (Garlic Mustard), Glechoma hederacea (Ground Ivy), Lamium purpureum (Purple Dead Nettle), Ranunculus ficaria (Fig Buttercup), Senecio vulgaris (Common Groundsel), Stellaria media (Common Chickweed) and Taraxacum sp. (Dandelion). Emerging everywhere, in abandoned lots, along the road side and along streams and wet areas is another nasty weed, Polygonum cuspidatum (Japanese Knotweed). Toxicodendron radicans (Poison Ivy) is beginning to leaf out so it is fairly easy to detect its shiny red leaves of three.

Central Region (Boylston) – General Conditions: The releatively cool weather has left many plants blooming for an extended period resulting in a very colorful, fragrant spring. Daffodils are nearly finished blooming now as are almost all of the minor bulbs but many early perennials and shrubs are in full swing, including Bottlebrush (Fothergilla gardenii), Spiraea thunbergii ‘Ogon’, Yellowroot (Xanthorhiza simplicissima), Helleborus, Bleeding Hearts (Dicentra spectabilis), Dutchman's Breeches (D. cucularia), Spring Beauty (Claytonia virginica), Lungworts (Pulmonaria rubra and P. angustifolia), Mukdenia rossii, Virginia Bluebells (Mertensia virginica), Trillium erectum and T. grandiflorum, Periwinkle (Vinca minor), Barrenworts (Epimedium sp.), Pigsqueak (Bergenia sp.), Moss Phlox (Phlox subulata), Woodland Phlox (P. divaricate and P. stolonifera), Rhododendron schlippenbachii, Primroses (P. seiboldii), Barren Strawberry (Waldstenia ternata), Hybrid Tulips (Tulipa cvs.), Grape Hyacinth (Muscari armeniacum), among others

Pioneer Valley Region (Amherst) - General Conditions: Chilly mornings with mild, sunny days describe the weather pattern of the last week in the Pioneer Valley. Soils are drying out. Deciduous trees are filling out their crowns and flowering trees and shrubs fill the landscape with color. Lawns continue to be green and lush while phlox and bleeding heart are beginning to bloom. Pests/Problems: Symptoms of leaf spots, shoot blight, and anthracnose are absent so far this spring.

Berkshire Region (Great Barrington) - General Conditions: The latter part of the reporting week has been sunny, windy, and dry. Yet, soil moisture levels are moderate and irrigation is not needed except for sandy sites. An intense but brief - about 10 minutes - hail storm occurred in certain parts of southern Berkshire County on Saturday, May 7. Only minor damage to plant foliage was noticed. Pollen levels are

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very high and allergy sufferers are miserable, notably this reporter. Pests/Problems: The usual pest suspects at this time of year are active: carpenter bees, wasps and hornets, brown dog and deer ticks, biting gnats, household pests (carpenter ants, red ants). Landscape pests observed this week are: Boxwood Leafminers (larvae still feeding within leaves), aphids (on euonymus), Pine Bark Adelgid (egg stage), Spruce Spider Mite (on dwarf Alberta spruce), Imported Willow Leaf Beetle. Dandelions are beginning to set seed.

Environmental Data The following growing-degree-day (GDD) and precipitation data was collected for an approximately one- week period, May 5 through May 11, 2011. Soil temperature and phenological indicators were observed on or about May 11, 2011. Total accumulated GDDs represent the heating units above a 50° F baseline temperature collected via our instruments for the 2011 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.

2011 GROWING DEGREE DAYS Soil Temp (°F at 4" Precipitation (1-Week Region/Location 1-Week Total accumulation for depth) Gain) Gain 2011

Cape Cod 26 144 60° 0.80"

Southeast 29 162 53° 0.60"

East 46.5 168.5 58° 0.80"

Metro West 35.5 155 54° 0.65"

Central 37 144 54° 0.48"

Pioneer Valley 27 153 62° 0.12"

Berkshires 37 175 58° 0.67"

AVERAGE 34 157 57° 0.59"

n/a = information not available

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 reporting period:

Indicator Plants - Stages of Flowering (begin, b/full, full, f/end, end)

SOUTH METRO PLANT NAME (Botanic/Common) CAPE EAST CENT. P.V. BERK. EAST W.

Spiraea x vanhouttei (Vanhoutte Spirea) begin * * * * * *

Lonicera tatarica (Tatarian Honeysuckle) begin * b/full * * b/full *

Rhododendron carolinianum (Carolina begin full * begin * full * Rhododendron)

Aesculus hippocastanum (Common begin full begin * * * begin Horsechestnut)

Syringa vulgaris (Common Lilac) begin full full begin b/full full b/full

Rhododendron spp. (Early Azaleas) begin full b/full full full full b/full

Cornus florida (Flowering Dogwood) - bracts begin full b/full begin full full begin

Malus spp. (Crabapple) begin full full full full b/full b/full

Cercis canadensis (Redbud) begin full full full full full full

Viburnum spp. (Early Fragrant Viburnums) full full full begin full full full

Amelanchier spp. (Shadbush, Serviceberry) full end f/end full f/end f/end full

Pyrus calleryana (Callery Pear) full end end f/end full full full

Chaenomeles speciosa (Common full f/end full f/end f/end full full Floweringquince)

Magnolia soulangiana (Saucer Magnolia) f/end end end end full end full

Prunus serrulata (Japanese Flowering full end end end end f/end full Cherry)

Rhododendron 'P. J. M.' f/end end end f/end full f/end full

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* = no activity to report/information not available

CAPE COD REGION - Roberta Clark, UMass Extension Horticulturist for Barnstable County, Barnstable.

SOUTHEAST REGION - Deborah Swanson, UMass Extension Horticulturist for Plymouth County - Retired, Hanson.

EAST REGION - Kit Ganshaw & Sue Pfeiffer, Horticulturists, reporting from the Arnold Arboretum, Jamaica Plain.

METRO WEST REGION – Julie Coop, Horticulturist, reporting from Acton.

CENTRAL REGION - Joann Vieira, Superintendent of Horticulture, Tower Hill Botanic Garden, Boylston.

PIONEER VALLEY REGION - Dan Gillman, Plant Pathologist, UMass Extension Plant Diagnostic Lab, UMass, Amherst.

BERKSHIRE REGION - Ron Kujawski, Horticultural Consultant, reporting from Great Barrington. Woody Ornamentals Insects Bud-opening on trees and shrubs is well underway across the state.

Hemlock Woolly Adelgid (HWA) - Infested trees with live HWA can be treated with a summer rate horticultural oil spray once weather conditions are conducive for such sprays. Also, systemic imidacloprid can also be effective but uptake by the plant and translocation to the growing points where HWA feeds can take anywhere from weeks to months given the size of the tree and delivery method (soil-applied vs. trunk injection). Wait until mid-late May for any systemic imidacloprid applications.

Elongate Hemlock Scale (aka: Fiorinia Scale) has become more prevalent in MA in recent years and is commonly found attacking hemlocks that are also under assault by hemlock woolly adelgid. This very small, elongate and light brown scale is found on the undersides of needles and can be difficult to see even when occurring in large numbers. Inspect for both pests on Eastern (Canada) hemlock. Systemic imidacloprid is not very effective for this scale nor are oil sprays. This scale is atypical given that it produces crawlers (first instar stage that is the easiest to manage for most scale species) throughout the growing season where other species have 1-2 crawler stages per year. Dinotefuran (Safari™), another neonictinoid, like imidacloprid, has systemic uses and does have this scale specifically listed on the label. Safari™ in MA is a restricted-use insecticide given its high water solubility.

Winter Moth (WM) caterpillars remain feeding on host plant foliage. Oak leaves are now emerging in much of the state and WM larvae have been found associated with those buds and foliage in eastern MA but the threat to oaks is yet to be determined. Overall, winter moth is expected to occur in scattered areas at outbreak numbers this year in eastern MA. Once buds have expanded sufficiently a spray with Bacillus thuringiensis (Kurstaki) or one that contains Spinosad as the active ingredient should provide the desired levels of control. Pyrethroids also work well at this time but tend to be much harsher on beneficial insects and non-target organisms.

Gypsy Moth counts appear to be low once again in MA. Hatch has now occurred. The (now) naturally occurring entomopathogenic fungus Entomophaga maimaiga is the controlling factor for this once very serious exotic invader in MA B.t.k or Spinosad products work very well for this caterpillar at this time.

Fall Cankerworm does not appear to have any strong footholds in MA at this time but it is not uncommon for small and isolated pockets of this native caterpillar to exist. Its favored host plant range is extensive but oaks and maples are common hosts. It can appear mixed in with winter moth populations and be easily confused with that pest but it has 2 ½ pairs of abdominal legs (prolegs) where winter moth has only 2 pairs. It also hatches a couple of weeks later than winter moth.

Eastern Tent Caterpillar has hatched and is starting to form silken webs in the crotches of branches of Malus and Prunus species. When occurring in large numbers, they are capable of defoliating their host plant. No large populations of this native caterpillar are expecting in MA this year. Reports from Cape Cod suggest that the heaviest areas of population in the state are there. Small infestations can be physically removed from the tree on cool nights when all of the young caterpillars are huddled in the still small silken webs. Bacillus thuringiensis (Kurstaki) can be quite effective for the younger caterpillars. Spinosad products work very well for caterpillars of all ages.

European Pine Sawfly (caterpillar) is now appearing on such host plants as mugo pine, among others. This dark caterpillar with black marking feed in clusters on the host plant. Small infestations can be pruned away and destroyed. Look now for the yellow blocky spots lined up along needles, which indicates the presence of eggs within the needles. In small infestations, infested needles can be pruned out and destroyed prior to the eggs hatching. When caterpillars are small, insecticidal soap sprays are quite effective. Spinosad products work very well on sawfly larvae of all ages.

Balsam Twig Aphid is active. Inspect the newest needles of firs, especially Balsam and Fraser for the tiny green aphids. This aphid causes the newly emerging foliage to become twisted with needles stuck together with the very sticky honeydew produced by this aphid. The damage is purely aesthetic but can make specimen trees unattractive while rendering host trees in Christmas tree plantations un-saleable. Oil sprays (summer rate now) can be effective bud be aware of newly emrging needles that are tender and more susceptible to phytotoxic reaction (‘needle burn’). Certain pyrethroids are also labeled for this aphid pest.

Hemlock Eriophyid Mite feeds openly on the upper surfaces of the host plant. Sign of infestation is usually chlorosis of the needles. Inspect closely for the barely visible peg-shaped and pale yellow mites on the needle surfaces. If necessary, treat with a horticultural oil spray at the summer-use rate.

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Boxwood Psyllid is active and its piercing-sucking feeding is causing new foliage to become cupped. By the time cupping is noticed, it is too late to treat. Foliage will not become yellowed or die but severe cupping of leaves can lead to severe aesthetic value loss. Systemic imidacloprid might be helpful to reduce the numbers of this pest for next year.

Snowball Aphid has been active on numerous viburnums, such as: Korean Spicebush, Mapleleaf, Cranberry bush, etc. Like the Boxwood psyllid, the only damage caused is curling of the foliage, which can be unacceptable when occurring in large numbers. Treatments are the same as with Boxwood psyllid. However, it is now too late for treatments in much of the state.

Lily Leaf Beetle adults are active. Asiatic lily foliage is now very present and these bright red adult beetles are causing noticeable notching of the foliage. Mating will occur within the next couple of weeks and then small rows of eggs will begin to appear on the foliage undersides. Inspect now for the beetles. If treatments are necessary a chemical pesticide, such as a pyrethroid, organo-phosphate, or carbamate, is usually required to obtain desired levels of control. The larvae, which won’t appear for a while, are easily treated with a product that contains Spinosad (e.g. Conserve SC™).

Viburnum Leaf Beetle - Inspect newly emerging foliage for what may appear as spotting. Inspect more closely to see the tiny pale-yellow larvae skeletonizing the leaves. Treat with a product that contains Spinosad. This pest has the potential to consume all of the foliage of the host plant within 4-5 weeks of larval feeding. This pest is commonly moved on nursery plants from other states that have had this pest for a number of years; inspect, carefully, any new plants arriving for installation.

Birch Leafminer are active (around the time that the leaves on the host trees are partially emerged from the buds; “when the leaves are about the size of a dime”). The adult female sawfly wasps are small and dark and can be observed visually on host plant foliage. Eggs are laid within the newly emerging leaves. The use of yellow-sticky cards (1 per tree) works extremely well for monitoring for this sometimes very serious pest. Once the adult sawflies have emerged, the tree can then be treated with a chemical insecticide, such as a pyrethroid, to prevent egg-laying within the foliage.

Emerald Ash Borer - Although not yet found in MA, it was found in a roughly 30 mile by 15 mile area in New York State just 25 miles from the western borders of MA and CT last July (2010). Both states are actively preparing now to monitor for this unwanted exotic invader. Traps will be set out throughout Berkshire County (MA) soon to monitor for the adult beetles, which begin to appear in June. For more information consult: http://www.emeraldashborer.info

Asian Longhorned Beetle - Survey work continues in the Worcester and Jamaica Plain Regulated Areas. No new finds have occurred in the Boston (Jamaica Plain) area since the original 6 trees at Faulkner Hospital were discovered and removed last July (2010). Within the Worcester Regulated Area, new pockets of infestation have been found. The latest find, in Worcester but bordering the town of Auburn, has lead to an expansion of the Regulated Area to now include a part of Auburn. No infested trees or beetles have been found in Auburn as of this time. The Worcester Regulated Area has expanded from being 94 sq. miles to now being 98 sq. miles. For more information consult: http://massnrc.org/pests/alb

Brown Marmorated Stink Bug has been officially found in MA 5 times within the past 4 years. This exotic pest caused millions of dollars in damage in some of the mid-Atlantic states this past fall in such crops as apples, peaches, corn and others. It is expected that this pest will become established in MA at some point. Please report any findings to MDAR or UMass Extension (Robert Childs: [email protected] ). A source for information and quality photographs for this pest is:

http://ento.psu.edu/extension/factsheets/brown-marmorated-stink-bug

* No new reports of Brown Marmorated Stink Bug were received this week for MA.

Reported by Robert Childs, Extension Entomologist, Plant, Soil and Insect Sciences Department, UMass, Amherst.

Diseases Closely examine last year’s spruce needles for evidence of Rhizosphaera needle cast infection to determine if the tree is particularly susceptible. On susceptible spruces, an obvious number of needles from the last several years are missing (cast off). In addition, the disease often discolors those still attached and these have stomata on their needles blackened by Rhizosphaera fruiting structures erupting through them. As buds break open and new needles develop, it is time to consider protecting symptomatic, high value spruce trees from Rhizosphaera needle cast. This disease is normally not severe enough to warrant fungicide protection. However, successive springs with cool wet weather when immature needles are developing, allowed the build-up of Rhizosphaera inoculum in some landscapes and Christmas tree farms. Fungicides act to protect immature needles from becoming infected. Where management is desirable, apply 2-3 treatments at 7-14 day intervals beginning needles emerge and shoot elongation progresses.

Flowering dogwoods susceptible to dogwood anthracnose are vulnerable to infection during rainy springs when immature leaves and twigs are developing. Apply fungicide to protect new growth on high value trees, as the buds break open, again when bracts have fallen, and ~4 weeks later. If this is a persistent problem, consider planting one of the many resistant cultivars of flowering dogwood and Kousa dogwoods now available.

Apply fungicides to protect emerging leaves on susceptible apple and crabapple from apple scab as the buds turn pink, again around petal fall, and if wet conditions linger, repeat them 1-2 additional times at 7-10 day intervals. In addition, prune trees to increase air circulation and sunlight penetration, which speeds drying of

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foliage as well as improves spray coverage. There are numerous resistant varieties of apple, crabapple, and mountain ash to grow and simplify apple scab disease management.

When plant surfaces are dry, remove and dispose of infected foliage to reduce juniper blight inoculum. Make the cut an inch or so below the boundary between dead and healthy tissue. Begin fungicide control ofjuniper blight caused by Phomopsis juniperovora as new growth emerges, and repeat applications if wetness persists. If the problem persists, consider gradually replacing problem junipers with disease- resistant shrubs better adapted to the growing site.

Maximize the effectiveness fungicide treatments in the management of black spot on rose by initiating them now as buds swell and repeat applications per label directions into the fall. Minimize duration of foliar wetness to further suppress black spot infections, by irrigating early in the day so foliage dries rapidly as day warms as well as growing plants in areas with good air circulation and sunlight. If the problem persists, gradually replace susceptible varieties of roses with those resistant to black spot to reduce infections and buildup of inoculum, as well as the need for fungicide treatments.

Gymnosporangium rust fruiting structures are now beginning to appear on the alternate hosts of eastern red cedar (really a juniper) and Rocky mountain juniper, as well as an occasional Chinese, common, creeping, and savin juniper. Specifically, cedar-apple rust galls are visible on eastern red cedar as eruptions of orange, gelatinous masses protruding from pea- to golf ball-sized galls. These fruiting structures release spores that infect apple and crab apple leaves at this time of the year during cool, rainy periods. Likewise, fruiting structures of quince rust are visible as red-orange “cracks” in the bark and small gelatinous masses on the foliage of infected branches on several of these junipers. Gymnosporangium rust infections seldom cause severe damage to host plants, but their brilliant colors bring attention to them when their fungal fruiting structures form on the foliage, fruit, and shoots of their broadleaf hosts. If desired, begin fungicide sprays at this time to protect leaves, green shoots, and fruit of susceptible, high value apple and crabapple as well as serviceberry, hawthorn, mountain ash, quince, flowering quince, and pear from infections.

Plant Problem Diagnostic Lab Woody Plant Report: The following are some of the interesting woody plant disease/abiotic disorder samples received at the UMass Extension Plant Diagnostic Lab in Amherst during the period from April 25 through April 29, 2011:

Hemlocks - a couple separate 10-35 year old hedges with some scattered brown needles and dying twig terminals as well as large areas without needles; the fungi Phomopsis and Fusarium were secondary colonizers of wet twig/branch bark wounds likely caused by winter damage, strong winds, shearing/pruning, or similar bruises. Pinus strobus ‘Pendula’ - ~25 year old tree with scattered twigs/branches turning brown in mid- summer during last 2 seasons; Diplodia shoot blight. Black Hills white spruce - ~40-year-old hedgerow began to show scattered browning of 1-year-old needles last fall and now more are browning and falling off; Rhizosphaera needle cast Eastern white pine - mature tree with needle yellowing/browning and branch dieback; Fusarium cankers secondary to usually innocuous insect feeding damage (some can act as carriers of the fungus) as well as wet wounds from heavy snow/ice load, strong winds, and other bruises. Microbiota decussata - 1-2 year transplants growing near sidewalk with foliage on 3 of 8 exhibiting from 10-90% branch dieback beginning at their root crowns; no root or foliar disease, but Phomopsis cankers consistently found in wounded branch pieces likely damaged by foot traffic and/or snow piled on plants during winter plowing.

Reported by Dan Gillman, Plant Pathologist, UMass Extension Plant Diagnostic Lab, Amherst. Landscape Turf Invasive crane flies - Those of you in the southeastern part of Massachusetts should be watching for emergence of the "common" crane fly, or sometimes called "marsh" crane fly (Tipula oleracea). Adults look like giant mosquitoes. Just before adults emerge, the pupal casings can be seen projecting out of the ground. This species has two generations per year, so the adults you may see flying will be laying eggs soon, which will develop into larvae that feed on the foliage and later on the roots of turfgrass. Keep in mind that there are several native species of crane flies as well, so it is important to collect specimens and get them to a specialist who can identify the insects to species. If you do see large numbers of crane fly adults flying, collect as many as you can, and contact us so we can put you in touch with Dr. Dan Peck, who has done most of the crane fly work in the Northeast.

Reported by Dr. Pat Vittum, Professor and Extension Entomologist, UMass Department of Plant, Soil and Insect Sciences, Amherst.

United States Department of Agriculture National Institute of Food and Agriculture

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http://extension.umass.edu/landscape/message/lm-112011[5/23/2012 12:52:15 PM] UMass Extension Landscape Message #11 - 2011 | UMass Extension Landscape Nursery & Urban Forestry | UMass Amherst

http://extension.umass.edu/landscape/message/lm-112011[5/23/2012 12:52:15 PM]