Defoliators:

Lepidoptera:

• Winter Moth is virtually finished feeding for this year. Overall, populations appeared lower than in recent past years. However, this is a resilient pest that has too few natural controls here in New England and will appear again next year, perhaps in larger numbers. Controls for this pest now are probably not warranted. In fact, any large populations of little green loopers that are now seen, especially in eastern MA, will most likely be fall cankerworm and not winter moth.
  
• Forest Tent Caterpillar (FTC) is close to maturity in the caterpillar stage. These caterpillars are now quite large and capable of consuming much foliage per caterpillar per day. However, feeding should cease within the next week to ten days, and pupation will begin. Oaks and maples are most susceptible, but many deciduous hosts are attacked.
  
• 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 caterpillar is now about halfway to its ultimate size in most of the state. No reports of large populations have yet been received. Monitor for their activity and treat if necessary. It is too late for Bacillus thuringiensis Kurstaki.
  
• Eastern Tent Caterpillar has pupated and is finished feeding for the year. Any caterpillars that remain on host plants or in the silken webs are most likely parasitized or diseased and are best left alone to help perpetuate these natural controls. Overall, numbers of this pest were much lower in the state than they have been for several years.
  
• Fall Cankerworm is reaching maturity in the larval stage. 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. Pockets of FCW have been reported from Martha’s Vineyard, Plymouth County, and Shutesbury (north Quabbin area in western MA). Treat, if necessary. Oaks and maples are common hosts.

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. Larvae are reaching full size; and if treatments are deemed necessary, a product that contains spinosad or one of the pyrethroids will work best at this stage.
  
• Azalea sawfly caterpillar is now approaching the end of its feeding cycle 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 which feeds mostly on the upper leaf surface of rose foliage by skeletonizing and, thus, creating a “window-paning” effect. Large numbers of this pest usually result in unsightly injury that can affect most of the foliage. Inspect for the damage and the presence of the small caterpillars. Treat with an insecticidal soap spray or with a product that contains spinosad. This pest is nearing the end of its feeding.

Coleoptera:

• Lily leaf beetle has been mating and laying eggs for several weeks now. Larvae have been seen feeding in the warmer regions of the state ( Amherst). Feeding injury, showing up as notches to leaf margins and holes in the foliage, are both quite obvious now. Larvae skeletonize the foliage and destroy it. 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 of the larvae, 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 chafer adults 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 budbreak 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 are now active, 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 has now produced the eggs for the second generation, which will be hatching soon.
  
• Most species of lacebugs are now beginning to appear in warmer regions. 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), a tiny and elongate-shaped scale, is 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.

Oddities:

• Periodical Cicada - Much national attention has been focused on the parts of the Midwest (e.g., Chicago area) where they are experiencing a peak year for the periodical cicada. This particular species emerges in the adult stage every 17 years and then disappears underground where it feeds on tree roots, as an immature, for the next 17 years. Witnessing an emergence of this species is an opportunity to experience one of the truly neat natural wonders of the insect world. Although appearing by the millions, they do not cause harm (although, sometimes, alarm). Periodical cicada has bright red eyes, and the males produce a ringing sound as their mating call. On warm and sunny days, the multitude of male cicadas ringing can reach decibel levels of close to 100. Since the media coverage has begun, Extension offices have received many calls asking if Massachusetts will have a peak year for this insect in 2007. The answer is no. We do have the remnants of a formerly large brood of periodical cicada on Cape Cod. The last peak year was in 1991, so the next peak year will not be until 2008, one year from now. However, we do have other species of cicadas that will be appearing later in the summer in much smaller numbers, such as the Dog Day Cicada. These are physically larger and don’t have red eyes. The males of these also produce a high-pitched buzzing sound as opposed to the ringing of the periodical cicada. Due to heavy people-pressure on the landscape of Cape Cod, populations of periodical cicada were much lower in 1991 than they were 17 years previous to that. We are waiting for next year to once again evaluate the health of this species on Cape Cod, where the bulk of this particular periodical cicada brood still exists in the state.

DISEASES -

Powdery mildew fungi are now barely visible as dusty, gray to white spots on horsechestnut leaves. Additional host plants including dogwood, sycamore, phlox, and rose 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 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 shootson sycamore, maple, and oak, while ash anthracnose appears as green leaves with curled brown blotches 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 treatments at labeled intervals.

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.

Reapply 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 -

No report this week.

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!