Landscape Message - Landscape Nursey and Urban Forestry

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The LANDSCAPE MESSAGE is an educational newsletter intended to guide landscape, nursery and urban forestry professionals in identifying pests in the landscape, monitoring their development, planning management strategies and creating site-specific records for future management reference.

UMass Extension has updated this issue to provide timely pest management information and the latest regional news and environmental data throughout Massachusetts. During the months of April through June, this newsletter will be published weekly. The next update will be available on or about May 22, 2009.

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2009 GROWING DEGREE DAYS

Soil Temp
(°F at 4" depth)

Precipitation
(1-Week Gain)

Total accumulation for 2009

n/a = information not available

* = no activity to report/information not available

Winter Moth larvae are very active. The numbers of winter moth caterpillars has increased markedly since a year ago in coastal MA. This pest can now be managed with a product that contains spinosad or with a registered pyrethroid product. Bacillus thuringiensis Kurstaki (B.t.K.) works when the caterpillars are small; it may be too late now for B.t to be effective.

Eastern Tent Caterpillars are now obvious on (primarily) Malus (apple) and Prunus (cherry) species. The growing larvae have constructed silken webs in the crotches of branches and move out of the web on warm days to forage on newly emerging foliage. Webs can be removed by pruning out and destroying, or larger populations can be treated with a product that contains spinosad or with one of the registered pyrethroids.

Gypsy Moth eggs have hatched now. Larvae are settled and feeding, primarily on oaks, but many deciduous species are attacked. Treat the same as winter moth, if necessary. Populations, overall, are expected to be low this year in MA.

Forest tent caterpillar will be active soon, if not already in the warmer regions of the state. Oaks and maples are common hosts, but many other deciduous trees can be attacked. If occurring in large numbers, treat with a product that contains spinosad or with one of the registered pyrethroid insecticides.

Euonymus caterpillar is active. Inspect euonymus for the yellow, hairless caterpillars with black spots. As they grow, they produce much silk throughout the plant. Heavy populations can cause much damage. If necessary, treat with a product that contains spinosad or with a registered pyrethroid insecticide.

European pine sawfly caterpillars are becoming active. Inspect host foliage (primarily mugo pine) for the yellow, blocky patches, which are the eggs embedded within the needles or look for the tiny dark-colored larvae clustered at the needle tips. This pest feeds voraciously and grows rapidly. Needles will be consumed down to the stems. Needles with eggs or stems with larvae can be pruned away and destroyed when this pest occurs in limited numbers. Otherwise, treat the larvae with a product that contains spinosad or use one of the registered pyrethroid insecticides. Very small larvae can be effectively treated with insecticidal soap.

Hemlock Woolly Adelgid (HWA) remains active and will continue to be quite active from now until approximately mid July. HWA can be managed with oil sprays at the summer rate, if the weather conditions are conducive for its application without harming plants, or with systemic applications of imidacloprid. (When using oil sprays, avoid tender new growth or conditions that delay drying time.)

Viburnum Leaf Beetle was found in MA during the 2008 growing season in several different counties. It was known to be established in Berkshire county for the past 3 years but has now been identified in Franklin, Bristol, and northern Worcester County. Many of the finds suggest strongly that this serious pest is being moved on nursery plants throughout the Northeast. Larvae are now actively feeding. Much damage can occur, especially from the larvae. For more details and preferred viburnum host species, visit:http://www.hort.cornell.edu/vlb Spinosad products work well for the larvae. Inspect viburnum twigs now for any signs of eggs; prune out and destroy if found.

Lily Leaf Beetle adults are very active, feeding on foliage of Asiatic lilies and mating. Eggs are now appearing on the undersides of lily foliage. Monitor for the bright red beetles and also for the eggs on the undersides of the foliage. Inspect the leaves for fine tan-colored, irregular-shaped lines about one inch long. On closer examination, these tan lines will be a row of eggs. When eggs are found, they can be removed and destroyed. Use pyrethroids for the adult beetles. Alter, when the larvae appear, a product containing spinosad works very well.

Asian Longhorned Beetle (ALB) was found in Worcester, MA last August. The Regulated Area is now at 64 square miles. Approximately 22,000 trees have been removed and rendered into wood chips since January 2009. It is estimated that this population may have been in Worcester for at least 15 years. Survey work has renewed within the Regulated Area, and it is already known that many more trees are infested. Everyone must be on the lookout for this pest and report any potential finds immediately if eradication efforts are to be successful. Also, take great care when moving firewood to avoid moving this very serious killer of forest and landscape hardwood trees.

To report a potential ALB find: http://massnrc.org/pests/alb
To see “How to Recognize ALB” slide presentation: recognize_alb_ppt.pdf

Balsam Twig Aphid is now very active. These pale green aphids feed on true firs, in particular; they feed on the new needles as they emerge from the buds causing them to twist and curl. This insect also produces much honeydew, which causes new (twisted) needles to stick together. This pest is of most concern in Christmas tree plantations but can be problematic in the landscape. If found in significant number, treat with a registered pyrethroid or with a horticultural oil if weather and plant phenology allows.

Snowball Aphid on certain viburnums is very active. The ‘stem mother’ has already caused new foliage to become curled. Unfurling these curled leaves will reveal the mother aphid. Soon, she will produce dozens of offspring that will continue to feed within the within these leaf curls until about the end of May. Treatments now are difficult; damage has already occurred in most cases. Soil applied (systemic) imidacloprid applied in August should carry over in the buds and be effective for next year’s population. Otherwise, a pyrethroid is most likely required if treatment is desired now.

Hemlock Eriophyid Mites remain active. These tiny, yet, just visible peg-shaped and 4-legged mites feed openly on the needle surfaces of hemlock. Inspect carefully for their presence. Affected trees often appear slightly chlorotic. These mites can cause harm if appearing in large numbers. They remain active until early to mid June. When found to be numerous on any particular hemlock, treat with an oil spray (weather permitting) or with one of the registered pyrethroid insecticides.

Inkberry Leafminer is a pest that overwinters as a larva within the foliage of inkberry. The characteristic brown leaf tips usually do not appear until January and, thus, get missed by many. Hold browned leaves up to the light to see if the leaf has been mined or cut into the browned area in search of the larva. If numerous mines are found, wait until mid to late May to hang yellow sticky cards on the affected plants. Once the adult flies appear, treat with a pyrethroid insecticide to kill the adults and to limit the incidence of re-infestation of the same plants. Foliage without mines but possessing browned tips may have experienced some winter injury.

Cottony Taxus Scale (a.k.a. Cottony Camellia Scale) is a pest on host plants including certain hollies, Taxus, and others. Inspect for sooty mold and white cottony egg sacs on the undersides of foliage. Host plants include certain hollies, Taxus, and others. Treat with a horticultural oil spray if proper plant phenology and weather conditions prevail.

Fiorinia Scale (a.k.a. Elongate Hemlock Scale) has become more prevalent in MA in recent years. Inspect the undersides of hemlock needles for the tiny, yet, often numerous scales. Stressed trees (those affected by compacted soils, drought, hardscape, etc.) tend to succumb sooner to this pest. Fiorinia scale produces crawlers throughout much of the growing season and is, therefore, difficult to manage. Oil sprays may help but usually require follow-up treatments. Systemic dinotefuran (Safari™) has been showing much promise for armored (hard) scales recently. However, it is a restricted use compound in MA.

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

See our disease fact sheets section for many helpful fact sheets on disease problems of trees and shrubs.

Flowering dogwoods susceptible todogwood anthracnose are vulnerable to infection during wet springs when immature leaves are developing. Apply fungicide to protect developing leaves 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 assuming wet conditions linger repeat them 1-2 additional times at 7-10 day intervals. In addition, prune the trees to increase air circulation and sunlight penetration that 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.

During dry weather remove and destroy 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 of juniper blight, caused by Phomopsis juniperovora, as new growth emerges. Repeat applications if wetness persists. If the problem persists, consider gradually replacing problem junipers with disease-resistant shrubs better adapted to the site.

Maximize the effectiveness of 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. Provide good air circulation and irrigate early in the day so foliage dries quickly in afternoon to minimize the period of plant wetness to further suppress black spot infections. 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 infections seldom cause serious damage to host plants, but their brilliant colors bring attention to them when the rust fungus infects the foliage. If desired, begin fungicide sprays at this time to protect leaves, green shoots, and fruit of apple and crabapple as well as serviceberry, hawthorn, mountainash, quince, flowering quince, and pear from infections. The 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 the 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.

Ramorum blight, also known as sudden oak death (SOD) and ramorum dieback: The Phytophthora ramorum detection, quarantine, and eradication survey completed its seventh year as a United States Department of Agriculture-Animal and Plant Health Inspection Service-Plant Protection and Quarantine (USDA-APHIS-PPQ) regulatory program in 2008. The program began by monitoring nine counties in California along with part of Curry County in Oregon. It focused on regulating movement of risk articles such as wood, soil, foliage, and nursery stock. Infested areas grew to 14 California counties and the larger part of Curry County in Oregon, which Oregon aggressively surveyed and treated since 2001. Discovery of a shipment of P. ramorum-infected Camellia plants from a large production nursery to many garden centers and retail nurseries nationwide resulted in the USDA-APHIS-PPQ regulatory program receiving a great deal of scrutiny and policy revision in 2004. As a result, in January 2005 USDA-APHIS-PPQ extended the regulation of nursery stock to the entire states of California, Oregon, and Washington. Through ongoing surveys of nurseries, USDA-APHIS-PPQ continues to define the extent of the pathogen’s distribution in the U. S. and limit its artificial spread beyond infected areas through quarantine and a public education program.

Status of Phytophthora ramorum in 2009:

Note: There were no updates for 2009 reported by USDA-APHIS-PPQ at this time. See earlier 2009 editions of the Landscape Message for a summary of the 2008 program.

Federal Regulation, State Inspection, Nursery Survey, and Other Finds. There was no report this month.

Forest Detection Survey. There was no report this month.

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

For a complete listing of upcoming events, see our Conferences and Workshops page.

Don't forget to visit the UMass Extension Online Weed Herbarium!

2008-2009 Professional Management Guide for Insects, Diseases and Weeds of Trees and Shrubs in New England - Pesticide label registration changes every year in all states and you can only legally apply pesticides according to the current year's label. This updated 2008-09 guide tells you what is current and legal for use in all the New England states and is the way for you to stay current with pesticide information. If you already have the 2003 version, this is the updated supplement for pesticide information. Remember, if you're a pesticide applicator, it's the law! Created by UMass Extension professionals, this manual offers the latest on virtually all the insects, diseases, and weeds of woody plants in New England; current and legal listings of chemical compounds labeled for the management of these pests; Integrated Pest Management (IPM) considerations for most of these pests; environmentally friendly alternatives in pest management such as horticultural oils, soaps, biologicals, etc.; and Growing Degree Day (GDD) information for most of the insect pests of woody plants. Click here to order online from the UMass Extension Bookstore or contact (413) 545-0895; eweeks@umext.umass.edu for information.

Planting and Maintaining Sustainable Landscapes: A Guide for Public Officials and the Green Industry - An updated and reprinted collection of fact sheets, including Trees and Shrubs for Low Maintenance Landscapes; Recommendations for Planting and Maintaining Trees and Shrubs; Integrated Pest Management and Plant Health Care; Streetscape Design and Planting; Selecting Turfgrasses for Low Maintenance Sites; Turf Pesticides and the Environment; Children's Protection Act and School IPM Plans; and Guidelines for Planting within the 100 Foot Wetland Buffer. Click here to order online from the UMass Extension Bookstore or contact (413) 545-0895; eweeks@umext.umass.edu for information.

UMass Extension Landscape Message #11
May 15, 2009

DIAGNOSTIC SERVICES

UMass Extension Landscape Message #11 May 15, 2009

DIAGNOSTIC SERVICES

UMass Extension Landscape Message #11
May 15, 2009