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 month of June, this newsletter will be published weekly. The next update will be available on or about June 26, 2009.

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Interested in additional turf-oriented content? UMass Extension Turf Program Management Updates

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 finished feeding about two weeks ago and are now pupating in the soil beneath the host trees. Trees that were severely defoliated should be kept watered during dry periods in hopes of successful refoliation.

Gypsy Moth are active but in extremely low numbers in MA this year. If necessary, treat the same as winter moth. Pupation will begin within the next two weeks.

Forest tent caterpillar remains active. Statewide, numbers are low, but a few ‘hot spots’ have been reported, especially in southeastern MA. Treat with a product that contains spinosad, if necessary. Also, the recent rains have set up the correct conditions for the natural spread of the Entomophaga fungus that kills this native caterpillar. Inspect tree trunks for mature larvae that die and later turn a rusty brown color, which is evidence of the presence and effect of this fungus.

Euonymus caterpillar has started pupation. Inspect their copious webbing for cocoons which appear to be large fuzzy grains of rice. The crisp white moths with black spots will appear within a couple of weeks. Damage from this pest has ceased in most areas of the state for this year.

European pine sawfly remain active. Inspect host foliage (primarily mugo pine) for the dark-colored larvae clustered on the needles. This pest feeds voraciously and grows rapidly. Needles will be consumed down to the stems. Treat the larvae with a product that contains spinosad or use one of the registered pyrethroid insecticides.

Mountain Ash Sawfly remains active. Inspect for the obvious larvae that consume all but the main veins of the host plant foliage. When found in significant numbers, treat with a product that contains spinosad.

Birch Sawfly caterpillars are active. Inspect for clusters of this pest and treat with a product that contains spinosad when found.

Roseslug Sawfly caterpillar - Inspect rose foliage for these small, pale-green sawfly larvae. They usually sit on the upper leaf surface and scrape away small areas of foliage at a time creating a ‘window-pane’ effect. Heavy populations are capable of causing the death of foliage from their severe feeding. If found in significant numbers, treat with an insecticidal soap spray or treat with a product that contains spinosad. Feeding from this pest is nearing its end for this year and may already be over in some regions.

Hemlock Woolly Adelgid (HWA) remains active. 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.) This insect will be quite active from now until approximately mid July.

Viburnum Leaf Beetle have finished feeding for this year. All viburnum leaf beetle larvae pupate by the middle of the month, and adult beetles will appear in July. These adults will be active until the first frost. This pest has made tremendous inroads into Massachusetts within the past two years and in some regions, defoliation of viburnum is severe. For more details and preferred viburnum host species, visit: http://www.hort.cornell.edu/vlb Spinosad products work well for the larvae.

Lily Leaf Beetle larvae are very active. Inspect the foliage of Asiatic lilies now for the feeding damage of the larvae and the larvae themselves. Treat larvae with a product that contains spinosad; use pyrethroids for the adult beetles. Lily leaf beetle has now been reported as being prevalent in Berkshire County (MA).

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 should report any potential finds immediately if eradication efforts are to be successful. Also, take great care when moving firewood to avoid transporting 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

White-spotted Pine Sawyer beetle (WSPS) adults remain very active. This longhorned beetle is native and not considered to be a pest as it attacks only already weak and dying pine trees. However, it strongly resembles the Asian Longhorned Beetle (ALB). The WSPS does not have a shiny jet-black color with crisp white spots as does the ALB. The WSPS also has one obvious and very distinctive white spot directly behind the head between where the wing covers (elytra) attach to the body. To view comparisons between the two species, see our “How to Recognize ALB” slide presentation: recognize_alb_ppt.pdf

Asiatic Garden Beetle remains active within the state. These beetles are a rust color and only appear at night to feed. Often they are attracted to lights. This beetle feeds on a variety of garden plants including, basil, peppers, and others as well as attacking landscape plants such as rhododendron. Inspect with a flashlight between 9:30 PM and midnight for their activity. If found in large numbers, treat with an insecticide that contains one of the registered pyrethroids.

Spider Mites are active. Cool-season mite species, such as spruce spider mite will build up in numbers on such hosts as spruce, fir, arborvitae and others and then go dormant when the hot weather arrives around July. They will then return to feed and multiply by late August and continue into the fall. Inspect the two and three year old growth for their activity. Treat when numbers become large. Warm-season species, such as the two-spotted spider mite, are also active and have a wide range of host plants. Populations of these remain active and thrive during the hottest times of the summer. Inspect weekly for increases in numbers and treat when necessary.

Native Holly Leafminer - Monitor American holly now for signs of mining by this pest. The larvae have over-wintered within the mines and have begun pupation. Adults should already be active in the warmer regions of the state. Place a yellow sticky card in infested trees to lure the adult female flies. As cards begin to fill up with these flies, apply a knockdown spray such as one of the registered pyrethroid insecticides to prevent re-infestation.

Arborvitae Leafminer adult moths will be active soon. No traps are available to monitor for their activity. Starting around mid-June, lightly shake branches of infested arborvitae and observe for the flight of tiny, dull-white moths. Treat with a registered pyrethroid insecticide when adult moths appear to break the cycle of re-infestation. Many parasitoids exist that greatly suppress populations of this leaf-mining pest within 2-3 years naturally.

Azalea Bark Scale - Monitor azaleas now for white cottony masses on stems or in crotches of twigs, the pink crawlers, and sooty mold. Sooty mold, a black fungus on the leaf surface, is an indication of a past or current infestation by this pest. Heavy infestations of the scale can have a severe effect on plant growth and aesthetics. If necessary, treat with soil applied imidacloprid.

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 soil, 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. Oils 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.

Pine Needle Scale - Now is the time to monitor pines (mostly mugo) for the presence of this white-colored scale on the needles. From a distance, a heavy infestation will give branches the appearance of being covered with snow. Crawlers will be active soon. Apply a spray of horticultural oil at the summer rate when crawlers appear. Crawlers are tiny and pale yellow. Monitor visually or use black electrical tape (wrapped sticky side out around a couple of fingers) to lightly daub the needles; inspect tape for yellow crawlers.

White Prunicola Scale crawlers are active. Inspect such hosts as Japanese cherries, lilac and privet. If left untreated, this pest can kill branches and entire plants. Treatments during the crawler stage are most successful. A horticultural oil spray or a systemic application of dinotefuran (e.g. Safari™) are most effective.

Dogwood Borer adult moths are becoming active. Pheromone traps are available to monitor for the emergence of this month. The primary host is flowering dogwood. Inspect the trunks of trees for oozing sap and wet sawdust at the site of entry. Avoid injuring the bark of dogwoods with mowers and line trimmers; wounds attract this pest and allow for ease of entry into the plant. Plants that become infested this year can be treated with a coarse spray of beneficial nematodes in August.

Lacebugs on shrubs have become active. Inspect the undersides of certain shrubs such as Japanese pieris/andromeda, rhododendron, evergreen azaleas, cotoneaster, and others for their activity. Plants in sunny growing sites have the potential to be severely injured by these insects over the course of the summer. Soil applied imidacloprid works very well at managing these pests. Horticultural oil sprays and insecticidal soap sprays also work for the immature stages, but the spray must be concentrated to the undersides of the foliage in order to cover the pest at the time of application.

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.

Mushrooms in lawns often develop from thatch, buried logs, dead roots, stumps, or even construction debris. They have many different sizes, colors, shapes, and habits of growth and develop fruiting structures or mushrooms in lawns after prolonged wet weather. The fungi that produce these mushrooms are beneficial because they decompose organic matter in the soil, making nutrients available to other plants. These mushrooms usually are harmless to grasses, but some people consider them unsightly or want to get rid of them because young children play in the area. Neither spray applications nor drenches of fungicides are effective in controlling these mushrooms. A simple way to remove mushrooms is to mow the lawn while collecting the clippings or by raking them up. Elimination of excess thatch and aerating the soil to improve water penetration also helps in some cases. In addition, the mushrooms gradually disappear without interventions if the weather becomes drier.

Horsechestnut (Guignardia) leaf blotch is visible, as scattered, irregular-shaped orange-brown blotches on infected leaves. They are primarily affecting lower, inside leaves. However, as the summer progresses the impact of the disease may be more noticeable, but chemical intervention at this time for this season is of little benefit. Keep in mind that horsechestnut infected year after year continue to grow vigorously in spite of Guignardia leaf blotch.

Powdery mildew fungi are visible as a dusty, gray to white spots on red horsechestnut (Aesculus x carnea) leaves. Additional host plants of other species of powdery mildew including dogwood, sycamore, phlox, and rose are just beginning to show signs of powdery mildew in the Amherst area. Once established on plants, powdery mildews grow superficially on both upper and lower leaf surfaces as well as green shoots and flower buds. They are obligate parasites and derive sustenance only from living host plants. They do this by using minute, tube-like structures (haustoria) that penetrate the epidermal cells and draw out material they need to survive. Later this summer spherical, black fruiting structures are visible with a hand lens on the underside of leaves in the dusty, gray mycelia. Generally, the damage caused by powdery mildew is of minor consequence to healthy plants and does not warrant chemical control if unsightliness is not a critical concern. If considering chemical control, there are a number of unconventional applied materials labeled to protect susceptible plants. They include summer horticultural oil, commercial baking soda preparations (sodium bicarbonate and potassium bicarbonate), anti‑transpirants, as well as a number of conventional fungicides. Chemical spray programs are most effective when begun just as symptoms of powdery mildew begin to show. Once powdery mildew is extensive on the plant, there is little benefit from chemical control that season. Applications need to coat both surfaces of all susceptible plant parts to prevent infection. Spray on a regular schedule, and repeat more often during warm, humid weather.

Oak leaf blister is showing up on red, white, and pin oak leaves as yellow‑green, puckered spots. This is not a serious fungal disease problem in our area. Yet, if a severe outbreak is occurring on high value trees, note that for future reference. Next spring, start chemical control activities just as buds open and repeat at labeled intervals if wet weather persists.

Sycamore, maple, oak, and ash anthracnose are evident now as dark-green to dark-brown curling leaves and shoots on sycamore, maple, and oak, while ash anthracnose appears as young green leaves falling from the trees with very tiny brown spots. Anthracnose is widespread on early leaves and shoots this year due to the abundance of inoculum on overwintering twigs and fallen leaves, as well as the consistently wet weather. It is too late this spring to apply protective fungicides. These diseases cause some premature leaf loss, but that is not going to seriously affect an otherwise healthy tree. In the fall, fine prune infected twigs if practical, as well as collect and dispose of fallen leaves. Promote drying of foliage by pruning and spacing plants to increase the penetration of sunlight and air circulation in and around plants.

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.

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 #16
June 19, 2009

DIAGNOSTIC SERVICES

UMass Extension Landscape Message #16 June 19, 2009

DIAGNOSTIC SERVICES

UMass Extension Landscape Message #16
June 19, 2009