Defoliators:

Lepidoptera:

• Winter Moth has been active for about a month now, depending on the specific geographic region of the state. Overall, North Shore areas tend to be a little ahead of South Shore and Cape Cod. What initially looked like booming populations has now lead to confusion about just how well the newly hatched caterpillars survived their first two weeks. Areas that appeared to have large numbers now suggest that larval mortality may have been high this spring, at least in some areas. This developing story is being closely monitored by Joe Elkinton’s lab, but the results will not be known for another week. Bud break and leaf expansion was slow and staggered this spring and may have affected winter moth, which relies heavily on buds being at a specific stage when they first hatch from the egg. It is not uncommon for winter moth populations to fluctuate up or down within a given area from year to year. However, this is a very prolific pest; and small populations can quickly become large populations within a year or two. North Shore areas tend to have high populations while Plymouth County and Cape Cod appear to have lower levels than last year. If winter moth caterpillars are present, they should now be treated with a product that contains spinosad or with one of the labeled pyrethroid insecticides.
  
• Forest Tent Caterpillar (FTC) is once again in big numbers and very active. The warmer regions are already experiencing defoliation, especially on oaks. The Connecticut River Valley region in MA (e.g., Greenfield to Springfield) already have experienced complete defoliation of trees that are typically late to have bud break, such as pin oaks. However, fully leafed and blossoming crabapples have also been defoliated. In Greenfield, FTC is now around one and a half to two inches in length while just 10 miles from there, in the slightly higher elevations, FTC larvae are a bit smaller. Last year, an Entomophaga fungus, similar to the one that attacks gypsy moth, was observed having an effect on FTC. Numbers of this pest do appear to be lower this year in central and eastern MA, and early indications are that FTC numbers are lower in western MA, as well, this year. This pest, when occurring in large numbers, can quickly defoliate trees. If necessary, treat the caterpillars with a product that contains spinosad or with one of the labeled pyrethroid insecticides. Oaks, maples, birches, crabapples, and many others are common host plants.
  
• Gypsy Moth is not expected to be in large numbers across the state, but it is not uncommon for small, localized areas to experience gypsy moth in outbreak proportions. This pest has hatched in most of the state and is settled and feeding, but no reports of large populations have yet been received. Monitor for their activity and treat in a similar fashion, if necessary, as for winter moth or FTC.
  
• Eastern Tent Caterpillar has been active for more than a month and is rapidly gaining in size. Webs on cherries and apples are numerous and quite large in the areas of heavy infestation. Some areas that have experienced outbreaks of this pest in recent years are reporting much lower numbers this year. If this pest is active in your area, it should be obvious by now. Feeding has ceased in warmer regions, and treatment now may not be required. If necessary, treat the same as the above-mentioned pests. This pest has only one generation per year.
  
• Fall Cankerworm is now active. FCW is very similar in appearance to winter moth but has two and a half pairs of prolegs on the abdomen where winter moth only has two pairs. This pest is sometimes found in mixed populations with winter moth on the same host plant. Treat, if necessary.

Hymenoptera:

• European pine sawfly has the potential to completely defoliate branches and entire plants. Monitor mugo pine, in particular, for clusters of this green caterpillar, which are almost the same color of the needles. The very young caterpillars can be successfully treated with an insecticidal soap spray while caterpillars of all ages can be treated with a product that contains spinosad or with one of the labeled pyrethroid insecticides.
  
• Azalea sawfly caterpillar is now active in much of the state. This pale green caterpillar is almost the exact color of the host plant foliage and often hugs the leaf margin while it feeds. Therefore, it is very cryptic, and much damage can be created before it is noticed. Only deciduous varieties of azalea are attacked, especially the 'Exbury' and 'Mollis' varieties. This pest is capable of creating total defoliation of the host plant. Treat established populations with a product that contains spinosad or with one of the registered pyrethroid products that is labeled for this pest.
  
• Rose Slug Sawfly Caterpillar (aka Roseslug) is a pale green caterpillar. It feeds mostly on the upper leaf surface of rose foliage by skeletonizing, creating a “window-paning” effect. Large numbers of this pest usually result in unsightly injury. Inspect for the damage and the presence of the small caterpillars. Treat with an insecticidal soap spray OR with a product that contains spinosad.

Coleoptera:

• Lily leaf beetle is now mating and laying eggs. Feeding injury, showing up as notches to leaf margins and holes in the foliage, are both quite obvious now. Eggs, on the undersides of leaves, in the form of an irregular tan-colored line about one inch in length are becoming more prevalent. Treat the adults with a registered and labeled pyrethroid. Later on, treat the larvae with a product that contains spinosad. NEEM products do work to deter feeding activity, but they need to be reapplied every 10-14 days for as long as the pest is active, which is much of the growing season. NEEM, therefore, is a good choice in smaller plantings of true lilies.
  
• Viburnum leaf beetle, although not yet commonly found in MA, is active in the larval stage. Inspect susceptible plants for dead twigs that have a “sandpaper” texture, which may indicate an egg-laying site. Also inspect for the yellowish-colored larvae that are now chewing holes in the foliage. This is a very serious pest and needs to be treated when found. Spinosad products work very well against the larvae. Report any finds of this pest to Bob Childs at UMass Amherst (413-545-1053 or rchilds@psis.umass.edu). For more information about this pest and to view high-quality photographs, visit the following Cornell University web site at http://www.hort.cornell.edu/vlb
  
• European chaferadults should start to appear within the next few weeks, especially in the warmer regions. This large scarab often goes unnoticed due to its nocturnal habits, but it sometimes clusters by the hundreds or even thousands on individual plants for mating purposes. While there, they can often create plant injury in the form of large ragged notches on the leaf margins. Rhododendrons are common host plants along with many others. If suspected, inspect at night with a flashlight for their presence. Treat with a pyrethroid, if necessary.

Piercing-Sucking Pests:  

• Many spider mite species are now active. Inspect foliage with a hand lens for their presence; also, make note of the ratio of predatory mites to spider mites. Spider mites are often present on plant foliage, and predatory mites usually keep their numbers in check. Treatments for spider mites are usually only necessary if populations of them are high and when numbers of predators are low.
  
• Many aphid species are now very active, such as snowball aphid on many different species of viburnum, aphids on various species of maples (including Japanese maple), and balsam twig aphid. Inspect for clusters of aphids, honeydew, sooty mold, and distorted foliage. Unlike most of the other piercing-sucking pests, aphid feeding usually does not result in yellow stippling injury. Treat large populations, if necessary, with a spray of insecticidal soap, or with a systemic application of a product that contains imidacloprid.
  
• Monitor for honeylocust plantbug. Now that honeylocust is well past bud break in most of the state, begin to inspect for this pale green nymph on host plant foliage. Vigorously shake stems over a piece of paper and inspect for numbers of this pest. If they are found in large numbers, an application of insecticide may be warranted. This pest is usually at its worst when it feeds while leaves are still expanding from the buds. If we experience cool weather that delays leaf expansion by many days, this pest can create much injury to the point of defoliation. It is one of those pests that are extremely difficult to predict as it pertains to levels of expected injury. We have seen cases where numbers were high, but the foliage quickly got out ahead of the pest’s ability to create much injury. Weather seems to be the determining factor in the level of sustained damage each year. Treat, if necessary, with an insecticidal soap or with a pyrethroid insecticide.
  
• Boxwood psyllid remains active. This tiny insect causes the new foliage to become very cupped, which is the only damage that it creates. Inspect cupped foliage for white cottony fibers and the presence of the insect itself. Adult psyllids will appear soon, which means that most of the injury to the plant has already occurred. Adults can be treated with a pyrethroid spray to help prevent reinfestation. There is one generation per year.
  
• Hemlock Woolly Adelgid - remains very active, and the white cottony masses are quite obvious right now. Once foliage has fully expanded, treat with a horticultural oil spray at the summer rate. Small populations can be treated with a systemic application of imidacloprid. This pest is actively feeding and will produce one more generation within the next several weeks.
  
• Most species of lacebugs have not yet appeared but will be active within a matter of weeks. Such hosts as Japanese andromeda, azalea, rhododendron, cotoneaster, hawthorn, and others should be monitored for any lacebug injury that occurred last year. If damage is noticeable, then one should expect large numbers again this year. Those species that attack shrubs usually overwinter as eggs that are embedded in the undersides of the foliage or in the shoots.

• Elongate hemlock scale (aka Fiorinia Scale), is a tiny and elongate-shaped scale found attached to the undersides of hemlock needles. It is a very serious pest and should be treated when found. It can often be mixed in with hemlock woolly adelgid on the same plant. Horticultural oil sprays work well, especially during the crawler stage (late May into mid June) and when sprays are targeted to the needle undersides. Some of the newer neonicotinoid products, such as Safari™ (Valent) are showing good results against armored (hard) scales and may work well for elongate hemlock scale. However, bear in mind that no published results have yet appeared for the efficacy of this product for this particular pest.

• Azalea bark scale is active. In particular, inspect the axils of branches and the main stem of the plant for small, white cottony masses. This pest also produces much honeydew, which generates much sooty mold. In this stage, it often resembles mealybugs. Treat with a horticultural oil spray at the summer rate or with one of the registered chemical insecticides.

• Galls, which are abnormal plant growths that have been stimulated by an outside organism, (usually an insect or mite species) are generally just curiosities. They are commonly found on oaks (mostly cynipid wasp species) and on maples and cherries (eriophyid mite species). Overall, galls that occur on the foliage or flower parts are not considered to be problematic, even when they are very obvious. Either way, once the galls appear, there is nothing one can do to treat them. Galls that form on the woody portions of plants often kill the shoot, branch or entire tree. Fortunately, these are not all that common.

DISEASES -

Horsechestnut (Guignardia) leaf blotch is just beginning to become evident, 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 now barely visible as dusty, gray to white spots on horsechestnut leaves. Additional host plants include dogwood, sycamore, phlox, and rose which are not showing signs of powdery mildew yet 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 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 faint, yellow-green, puckered spots. This is a 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 with very tiny brown spots falling from the trees. 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. 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.

Now that buds are opening and new needles are developing it is possibly time to protect susceptible, high value spruce trees from Rhizosphaera needle cast. This disease is normally not severe enough to warrant fungicide protection. However, three (and now maybe four) springs in a row of cool, wet weather, as immature needles are growing, resulted in an increase in this disease in landscapes and Christmas tree farms. Check last year’s shoots for evidence of Rhizosphaera needle cast infection to determine if the spruce is particularly susceptible. On susceptible trees considerable numbers of needles from the last several years are missing (cast off). In addition, those still attached often have several stomata on their needles blackened by the Rhizosphaera fruiting structures that are releasing spores at this time of the year. Fungicides act to protect immature needles from becoming infected. Where management is desirable, apply 2-3 treatments at 7-14 day intervals beginning now.

Flowering dogwoods susceptible to dogwood anthracnose are vulnerable to infection during wet seasons. Reapply fungicide to protect developing leaves on high value trees when the bracts fall and repeat it about four weeks later. If this is a persistent problem, consider planting one of the many resistant cultivars of flowering dogwood and Kousa dogwood now available.

During wet weather, continue to protect susceptible Douglasfir from Swiss and Rhabdocline needle cast infections as needles emerge from buds until they expand to full size. Determine if the Douglasfir is vulnerable to infection by examining the needles closely for the fruiting structures of Rhabdocline needle cast. They are visible as elongated, red-brown spots and bands on infected needles. Needle discoloration is similar for Swiss needle cast; however, spore release occurs through black fruiting structures erupting out of needle stomata.

Apply fungicides to protect emerging apple and crabapple leaves from apple scab around petal fall and follow this 1-2 additional times at 7-10 day intervals (assuming wet conditions linger). In addition, prune densely branched trees to increase air circulation and sunlight penetration that speeds drying of foliage. There are numerous resistant varieties of apple, crabapple, and mountainash to grow and simplify disease management.

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 to minimize the period of plant wetness to further suppress the disease. If the problem persists, gradually replace susceptible varieties of roses with those resistant to black spot to reduce buildup of inoculum and the need for fungicide treatment.

Ramorum blight , also known as sudden oak death (SOD) and ramorum dieback. Since 1995, oaks and tanoaks have been dying in the coastal counties of California. Since then, surveys found other plants infected or associated with this disease caused by the water mold Phytophthora ramorum . Researchers in the U. S. first isolated the pathogen in Mill Valley ( Marin County) on tanoak, but since that time additional surveys confirmed the pathogen on various native hosts in fourteen coastal California counties and in Curry County, Oregon. 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 2007:

Forest Detection Survey - There was no report this week.

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

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

WEEDS -

DISEASES -

No report this week.

WEEDS -

Germinating crabgrass has been observed in areas of thin turf and non-turf areas. Begin monitoring for crabgrass. Those sites that are on a split-application program and were treated with the first application in early April are ready for their second application. If you see a large number of crabgrass plants now, consider replacing your second preemergence split with a postemergence application.

Dandelion, violets, and ground ivy are done flowering and postemergence herbicide applications can begin now. Postemergence herbicide combinations that contain triclopyr should be used for wild violets. Spring treatment will usually not provide complete control with one application. Retreat at first sign of regrowth or accept partial control for the time being and retreat in September.

Reported by Randall Prostak, Weed Specialist, UMass Extension Landscape, Nursery and Urban Forestry Program, Amherst.

IMPORTANT INFORMATIONAL RESOURCES

UMass Turf Research Field Day is Wednesday, June 20, 2007 at the Joseph Troll Turf Research Center in South Deerfield, MA. For complete information, visit http://www.umassturf.org/education/annual_events/field_day.html or e-mail fieldday@umassturf.org with questions.

The MNLA/MFGA Summer Meeting and Trade Show is Wednesday, July 18, 2007 at the Tower Hill Botanic Garden in Boylston, MA. Visit http://www.mnla.com for complete information.

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

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