UMass Extension Landscape Message #9 - 2011

Happy Arbor Day!

Scouting Information by Region

Regional Notes

Cape Cod Region (Barnstable) – General Conditions: The general trend is towards milder weather, with daytime highs in the upper 50F’s to low 60F’s and night time temperatures in the low 50F’s. The exception was Saturday, April 23, when a daylong wind and rain event kept temperatures in the 40F’s. Soil moisture is still adequate for planting and transplanting. Lawn mowing season has begun on lawns fertilized last fall. Dandelions and violets are blooming. Pests/Problems: Winter moth caterpillars are active within buds of blueberry and apple. Grubs are close to the surface and crows and grackles are damaging lawns in search of them. White pine weevil is active and, as temperatures warm up, Black turpentine beetle will also be active. Lily leaf beetle adults have been observed. Cutworms have been observed in turf. Dog ticks are active along with deer tick adults. Wasps are seeking nesting sites. With Forsythia in full bloom, crabgrass seed will be germinating.

Southeast Region (Hanson) – General Conditions: It is a repetitive phrase, but cool weather continues to keep plant growth in check. Hanson is 67 GDD behind last year. Lawns are finally starting to grow and to green-up.  Many lawns appear damaged due to snow mold and vole damage. Hanson received 0.50 inches of rain this past week and soils are moist. Sugar maple, Norway maple,  Prunus ‘Holly Jolivette' , Acer triflorum, Magnolia x loebneri ‘Leonard Messel’,  Magnolia x kewensis (M. kobus x M. salicifolia) ‘Wada’s Memory’,  Flowering Quince, Rhododendron ‘Olga Mezitt’, Pieris 'Brouwer's Beauty', Pieris floribunda (Mountain Pieris), Pieris japonica, Star Magnolia, Forsythia, Lindera benzoin (Common Spicebush), Corylopsis spicata, Stachyurus praecox, Lonicera standishii x fragrantissima, Spiraea thunbergii ‘Ogon’ , Abeliophyllum distichum (White Forsythia), Pachysandra procumbens (Alleghany Spurge), Pachysandra terminalis (Japanese Pachysandra), Epimedium sp.,  Trillium sp.,  Glaucidium palmatum, Brunnera macrophylla, Phlox subulata, Erythronium americanum (Trout Lily), Sanguinaria canadensis (Bloodroot), Helleborus niger, H. foetidus, H. x hybridus, Corydalis solida, Corydalis ‘Canary Feathers’, Corydalis scouleri, Omphalodes verna, Petasites japonicus (Japanese butterbur), daffodils, Scilla sibirica, Uvularia grandiflora (Large-flowered bellwort), Dutchman's Breeches, Primula sp., Anemones, Pulmonaria, Tulips, Violets, and Vinca minor are in full bloom. Cornus mas (Corneliancherry Dogwood) and Cornus officinalis and are ending bloom. Pests/Problems: Hemlock woolly adelgid, wasps and hornets, carpenter bees, mason bees, lily leaf beetle adults, black flies, mosquitoes, deer and dog ticks are all active. Continue to check for ticks frequently, especially after yard cleanups. Oak tree buds are still tight in many areas, however, winter moth caterpillars were observed on the buds waiting for them to open. In other areas, oak buds have started to swell and 1st instar winter moth caterpillars were found inside the buds. Winter moth caterpillars were also found in Norway maple, silver maple, Japanese maple, sugar maple, crabapple and apple.  Continue to monitor developing buds on susceptible plants (oak, birch, maple, blueberry, apple, crabapple, etc) with a history of winter moth damage and manage early to minimize damage. Massachusetts invasive plants like barberry, autumn olive and burning bush will be blooming soon and then start producing seed. Now is a good time to prune or shear the plants to remove flowers and potential seeds. Alternatively, shrubs may be pulled out and destroyed. Skunks are digging up lawns and deer continue to browse. Ranunculus ficaria, Violets, chickweed, bittercress, and dandelions are in full bloom.  Japanese knotweed has started to grow.  

East Region (Boston) – General Conditions: We had another cool week with the exception of April 24th, when we reached a high of 74° F.  We gained only 16 GDDs this week, bringing us up to 57.5 GDDs, 80.5 GDDs behind 2010. The Forsythia x intermedia (border forsythia), Magnolia sp. (magnolias) and Prunus sp. (cherry) are displaying the majority of color in the landscape. Several rhododendrons are also in flower: Rhododendron fargesii (Father Farges rhododendron), Rhododendron mucronulatum (Korean rhododendron), Rhododendron praevernum (February rhododendron) and Rhododendron shleppenbackii (royal azalea) is just starting.  Many plants are flowering but not receiving much attention; Ribes aureum (golden currant) is flowering alongside the not quite as showy Ribes alpinum (alpine currant) and in several locations the unpretentious Xanthorhiza simplicissima (yellow-root) is also in flower.  Also out of the limelight but spectacular in their own way are the Acer palmatum (Japanese maple), Acerp pseudosieboldianum (Korean maple) and Acer tegmentosum (striped maple) with their bright red flowers dangling as the leaves are just unfurling.  The first show of color from the Lilac Collection is Syringa x hyacinthiflora ‘Nokamis’ (hybrid lilac) and Syringa oblata (early lilac) which have a few flowers opening up with much more to come. Pests/Problems: Weeds continue to be the most noticeable pest in the landscape.  Capsella bursa-pastoris (shepherd's purse), Lamium purpureum (purple deadnettle), and Taraxacum officinale (dandelion) among others are in bloom.  The cool temperatures have kept the Operophtera brumata (winter moth) a bit lethargic but that could change in a matter of days.  The Lilioceris lilii (Lilly Leaf Beetle) is busy devouring the foliage of Lillium sp. (Lily).  Mature Cephalotaxus sinensis (Chinese plum yew) are in full flower and dispersing an abundance of pollen.

Metro West (Acton) – General Conditions: Cooler temperatures this past week have prolonged bloom and the landscape is aglow with color from all the flowers of the yellow forsythia, the lavender pink 'PJM' rhododendrons and the varying shades of pink and white on all the different species and cultivars of Prunus (Cherry) and Magnolia.  Other woody plants in bloom are: Amelanchier spp. (Shadbush, Serviceberry), Chaenomeles speciosa(Common Flowering Quince), Lindera benzoin (Common Spicebush), Pieris japonica(Japanese Pieris), Rhododendron mucronulatum(Korean Rhododendron) and R.‘Floda’ (Cultivar of Rhododendron). Perennials and spring ephemerals in bloom are: Bergenia cordifolia(Pig Squeak), Chionodoxa luciliae(Glory of the Snow), Claytonia virginica (Virginia Spring Beauty), Crocusspp. (Crocus), Dicentra canadensis (Squirrel Corn), D. cucullaria (Dutchman’s Breeches), D. spectabilis (Old Fashioned Bleeding Heart), Helleborous niger (Christmas Rose), Hyacinthussp. (Hyacinth), Mertensia virginica (Virginia Bluebells), Muscari sp. (Grape Hyacinth), Narcissusspp. (Daffodil), Primulaspp.(Primroses), Sanguinaria canadensis (Bloodroot), Scilla siberica (Siberian Squill), Trillium erectum (Red Flowering Trillium), Tulipa sp. (Tulips), Vinca minor (Periwinkle) and Viola spp. (Violets).  The cooler temperatures and moist soil make for excellent planting and transplanting weather. Pests/Problems: Ticks, mosquitos and black flies are all feeding and active.  Many weeds are in flower including 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).  Alliaria petiolata (Garlic Mustard) is ready to flower.

Central Region (Boylston) – General Conditions: Periodic warmth has pushed the bloom along.  Narcissus cultivars are in full bloom and hybrid tulips are beginning. Periwinkle (Vinca minor), Pig Squeak (Bergenia cvs.), Helleborus, Bleeding Heatrs (Dicentra spectabilis), Dutchman's Breeches (D. cucularia), Spring Beauty (Claytonia virginica), Bloodroot (Sanguinaria canadensis) , Lungworts (Pulmonatia rubra and P. angustifolia), Mukdenia rossii, Virginia Bluebells (Mertensia virginica) are all showing color and/or blooming. Many leaves are starting to emerge on trees and shrubs. Pests/Problems: Black flies are out and biting!

Pioneer Valley Region (Amherst) - General Conditions: Cool rainy weather continues to prevail. Flowers on trees, shrubs, and bulbous plants that are blooming appear to be holding-up well. Lawns with browned patches likely caused by snow mold this past winter continue to green-up.Pests/Problems: Soils remain wet with water standing in many low-lying areas.

Berkshire Region (Great Barrington) - General Conditions: There were dramatic changes in weather. Wet snow, followed by sleet and then rain marked the start of April 23.  The following day, the temperature reached 70° F and on April 26, it was 80° F.  The sudden warmth spurred plant growth.  Besides the plants listed below, Norway maple, pachysandra (P. terminalis and P. procumbens), and boxwood (Buxus sempervirens) are in bloom.  Cornus mas continues to bloom. Pests/Problems: While plant development accelerated, no plant pests have yet been observed other than boxwood leaf miner larvae.  Indoor nuisance pests i.e. spiders, ladybugs, boxelder bugs, and western conifer seedbug however are visible and active.  Adult tick populations remain high, and tick bites are very common.

Environmental Data

The following growing-degree-day (GDD) and precipitation data was collected for an approximately one-week period, April 21 through April 27, 2011.  Soil temperature and phenological indicators were observed on or about April 27, 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.

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:

• 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

Temperatures are finally starting to warm as we reach the end of April.  Much cool and wet weather throughout most of the month has kept insect activity to a slow start.

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) eggs hatched a couple of weeks ago and host plants with swelling buds were attacked by the tiny caterpillars wriggling into the expanding new foliage and flowers.  Norway maples, blueberry and others are common hosts at this time for winter moth caterpillars.  Oaks are another preferred host but generally break bud later than maples and thus preclude the tiny larvae from entering the buds.  Cool weather and other factors that delay bud opening can result in much damage to leaf and flower buds, especially when many larvae exist per bud.  Some areas of Rhode Island have reported as many as 12 caterpillars per bud in some plants within the past week.  Overall, winter moth is expected to have scattered areas of 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.   

Gypsy Moth counts appear to be low once again in MA.  Hatch occurs between 90-100 GDD, which is historically May 7th in Amherst, MA.  The (now) naturally occurring entomopathogenic fungus Entomophaga maimaiga is the controlling factor for this once very serious exotic invader in MA.  Amelanchier (e.g. shadbush, serviceberry, etc.) has begun to bloom in the warmer regions of the state and this is a phenological indicator for gypsy moth egg hatch. (egg hatch = 90-100 GDD).

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.  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) will be appearing soon 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, which are known as ‘stem mothers’.  These will be feeding for the next 1-2 weeks and then they will produce offspring that feed on the newly emerging foliage for this season.  It is this large population of aphids that 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.  If this pest is found in significant numbers now, treat with a horticultural oil spray at the summer rate.  Certain pyrethroids are also labeled for this aphid pest.

Hemlock Eriophyid Mite feeds openly on the upper surfaces of the host plant.  Signs 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 rate.

Lily Leaf Beetle adults are active. Asiatic lily foliage is now appearing and these bright red adult beetles are beginning to cause notching of the foliage.  Mating will not occur until sometime in May and then small rows of eggs will begin to appear on the foliage undersides.  Inspect soon 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 terminal stems of branches and main shoots of viburnum for the over-wintering eggs, which are embedded within the stem along the last 6-10 inches of growth.  These eggs appear as raised bumps along the stem.  Prune out and destroy any shoots that contain eggs now.  Larvae will hatch from the eggs any day now and begin to feed on expanding foliage.  These are easily managed 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 is becoming 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, 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.

House-invading insects - Those insects that seek shelter in homes, such as: ladybugs, boxelder bugs and western conifer seedbug have been awakening from their winter dormancy and seeking access to the outdoors.  Too often, they make a wrong turn and end up in living spaces in homes.  It is not uncommon at this time to find these insects (indoors) around windows and doors.  None of these create damage inside the home but are unwanted pests.  Vacuuming or sweeping them out should be effective.  A new pest that falls into this category is the brown marmorated stink bug and it 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: rchilds@psis.umass.edu). A source for information and quality photographs for this pest is:

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

* Since last week, one more positive find of Brown Marmorated Stink Bug in MA was submitted to UMass Extension; this time from Mashpee, MA

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

Diseases

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 dogwood 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 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 (PDF)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.

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 11 through April 15, 2011:

• Viburnum setigerum ‘Aurantiacum’ - scattered dieback affecting ~20% of branches on a mature shrub; the fungus Cytospora was a secondary colonizer of wet bark lesions likely caused by winter injuries, insect feeding damage, or similar minor bruises.
• Boxwood - 5-10 year old hedge with yellow-brown stippling of leaves; no leaf spot disease, but significant boxwood mite feeding damage.
• Eastern redbud - only 2 of 7 eastern redbuds planted 9 years ago remain on site due to persistent branch dieback; no vascular wilt disease detected, but Botryosphaeria fungus grew out of cambium/sapwood tissues, which disrupted water transport when cankers girdled branches and stems

Reported by Dan Gillman, Plant Pathologist, UMass Extension Plant Diagnostic Lab, Amherst.