LPM 6-11-2010

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. The message will be updated weekly during the month of June, and bi-weekly throughout the months of July, August and September. The next update will be available on or about June 18, 2010.

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2010 GROWING DEGREE DAYS

Soil Temp
(°F at 4" depth)

Precipitation
(1-Week Gain)

Total accumulation for 2010

n/a = information not available

* = no activity to report/information not available

Emerald Ash Borer (EAB) Update - As we are all aware, this invasive wood-boring beetle has been the demise of 10’s of millions of ash trees within the past 8 years in North America. Although not yet found in New England, it is ‘on the doorstep’. The USDA on Cape Cod has been actively involved with bio-control efforts for several years now. They are about to receive a new parasitic wasp from Russia to work on in quarantine to discern its effectiveness against EAB. This kind of work also entails discovering if the bio-control agent (in this case, a parasite) poses any threats to native species. There is currently a request for assistance for finding dying trees that are infested with native wood-borers. If any arborists, foresters, tree wardens, etc. know of any trees that currently have active infestations of native wood borers, such as bronze birch borer, two-lined chestnut borer, and others, please contact Bob Childs ASAP at rchilds@psis.umass.edu and the information will be forwarded to the USDA.

White-spotted pine sawyer adult beetles have been active for the past 2 weeks. The adult of this native species of longhorned beetle greatly resembles that of the Asian longhorned beetle (ALB). Many calls have been received about concerns of seeing this beetle, which is not harmful to healthy trees in North America. The Massachusetts Department of Agriculture (MDAR) has created a very informative pocket guide for distinguishing the two species. It is easily downloaded and printed out at the following address: http://massnrc.org/pests/albdocs/ALBPocketGuide.pdf ALB adults will not begin to appear until mid-late July in MA.

Winter Moth - This caterpillar has now finished feeding for this year.

Euonymus Caterpillar began pupation last week in the warmer regions of the state and will be entirely finished creating damage to host plants statewide any day now.

Mountain Ash Sawfly continues to feed. Inspect host plants for clusters of these yellow caterpillars with black spots. Prune away small clusters of larvae and destroy. For larger populations, treat with a product that contains Spinosad or with one of the labeled pyrethroid insecticides.

Viburnum leaf beetle larvae are now finished feeding statewide and this pest is currently in the soil undergoing pupation. The adult beetles will begin to appear around the middle of July and continue to emerge and feed until the first frost in the autumn. Adult beetles are capable of defoliating host plants. Treat adult beetles with a labeled pyrethroid or organophosphate insecticide when they appear.

Lily Leaf Beetle - These bright red adult beetles continue to be active but their numbers are waning. Eggs have been prevalent on the undersides of the leaves for a couple of weeks and larvae are beginning to appear and feed. Larvae are capable of causing tremendous damage in a matter of weeks. Spinosad products work well to kill the larvae.

Asiatic Garden Beetle adults are also active. The small, oval-shaped and rust-colored beetles are night feeders and can cause ragged notches to appear on evergreen host foliage, such as rhododendron. This pest is also problematic in vegetable and herb gardens as well. Monitor starting around 9:30 PM for adult beetle activity. Treat with a registered pyrethroid if large numbers exist.

Hemlock Woolly Adelgid remains very active. Horticultural oil sprays work well on all life stages of this pest but be watchful of hot days, cold temperatures at night and tender new plant growth. Systemic imidacloprid is effective, as well, but soil applications may take 2-3 months before they are fully systemic within a large tree. Heavy populations of HWA may need to be reduced first with a chemical insecticide or oil spray before the systemic can begin to perform.

Aphids continue to appear on a variety of host plants. Large numbers can reduce plant growth, create much sticky honeydew and lead to problems with sooty molds. Treat infested plants with insecticidal soap sprays or with a systemic application of imidacloprid.

Cottony Camellia (Taxus) Scale is active on such hosts as holly (merserve), Taxus, others) and starting to produce eggs. Inspect plants for sooty mold on upper leaf surfaces and then inspect the undersides of foliage above that for the scale. Female scales are slightly oval and brown while their attached egg sacs are very white. Treat with a horticultural oil spray targeted to the bottom sides of the leaves or use a systemic application of imidacloprid. Crawlers should begin to appear (from the eggs) around the middle of June this year.

Cottony Maple Scale is also producing eggs and can be found on such hosts as: maples,(silver maple in particular), dogwoods, linden, and other deciduous hosts. Treat the same way as Cottony Camellia Scale. Crawlers will start to appear around mid-late June this year in MA and continue into early July.

Pine Needle Scale crawlers are active in many regions of the state. Mugo pine is a common host but other pines are susceptible. Crawlers can be treated with a horticultural oil spray.

Euonymus Scale crawlers are becoming active. Use black electrical tape (sticky side out) to gently daub foliage and stems where scale is present to monitor for the crawlers, which are yellow to orange and pollen-sized. Once active, treat crawlers with an application of horticultural oil.

Spruce Spider Mite remains active on spruce and hemlock primarily. Inspect carefully with magnification for these two-tone colored mites. They tend to be more prevalent on the 2-3 year old foliage. If large numbers begin to become evident or if the plant experienced damage last year then treatments may be necessary.

Two-spotted Spider Mite remains active on a variety of host plants. This warm-season spider mite species will only become more prevalent as warm to hot weather continues. Inspect for chlorotic foliage that is finely stippled. Mites can be found primarily on the leaf undersides.

Lacebugs on Shrubs are actively feeding in the nymph stage. Plants that were severely affected last year (and if in growing in sunny locations) are at a higher risk for attack this year. Soil applications of a systemic imidacloprid product may still be applicable at this time. Inspect such plants as: Japanese andromeda, azalea, rhododendron, hawthorn, and others.

Arborvitae leafminers are now undergoing pupation and moths should appear within a few weeks. Inspect foliage for browned needles. Those affected by leafminer will have a small entrance / exit hole on the leaf underside. There are two species of Arborvitae leafminer in MA and the damage of both is very similar. One species pupates within the mine while the other leaves the mine as a caterpillar and spins a tiny (rice grain size) white cocoon on the foliage; usually the underside. Very tiny moths can be seen by mid-late June, which is the best opportunity for control. Eggs are laid on the leaf surface and the newly hatched caterpillars then bore into the foliage. Browning from mining generally does not appear until January. Monitor for adults by gently shaking the branches. These leafminers can also attack juniper.

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

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. 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 mid that horsechestnut infected year after year continue to grow vigorously in spite of Guignardia leaf blotch infections.

Azalea leaf and flower gall is a disease causing concern at this time. The fungus Exobasidium vaccinii causes it. Because of very rainy conditions last spring, galls are quite abundant on susceptible plants. In landscape plantings, the disease is more alarming than damaging. To prevent new infections, it is important to remove galls before the white spore layer appears on the gall surface. Once galls are white, removal actually aids dispersal of Exobasidium spores. However, high value plants in commercial settings may warrant a combination of gall removal and fungicide applications. Fungicides labeled include copper salts of fatty and rosin acids, mancozeb, thiophanate methyl plus chlorothalonil, and triadimefon. Begin applications just before leaves unfurl in spring. If wetness persists, make additional application at label intervals. As flowers and new leaves emerge on susceptible azaleas, new infections will not be evident until next spring. If the weather continues to be dry, there will be few new infections whether gall removal occurs or not. Spores require young leaves and flowers several hours for them to germinate and infect new tissues.

Now that new needles are developing it is time to consider protecting susceptible, 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 landscapes and Christmas tree farms. Closely examine last year’s needles for evidence of Rhizosphaera needle cast infection to determine if the spruce is particularly susceptible. On susceptible trees, a considerable number of needles from the last several years are missing (cast off). In addition, those still attached often have numerous stomata on their needles blackened by the Rhizosphaera fruiting structures that release spores at this time. Fungicides act to protect immature needles from becoming infected. Where management is desirable, apply 2-3 treatments at 7-14 day intervals beginning promptly.

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 2010:

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.

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Visit the Network for Environmental & Weather Applications (NEWA) web site for pest information, crop management information, and weather and climatic information (including GDDs) for a network of reporting stations throughout NY, VT and MA.

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.

Please Note: This is an abbreviated version of this pest message. Please go to http://umassgreeninfo.org/landscape_message/landscape_message.html for the message in its entirety

UMass Extension Landscape Message #15 June 11, 2010

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