Defoliators:

Lepidoptera:

• Gypsy Moth has pupated, and adult moths are active.
  
• Mimosa webworm webs are beginning to appear on honeylocust. This caterpillar ties foliage together loosely into pouches. It then skeletonizes the foliage from within these loosely connected leaflets. When occurring in large numbers, this pest can kill virtually every leaflet on a tree by late August. Foliage remains intact but dies and then turns brown. Treat with a product that contains spinosad, or use one of the labeled pyrethroid insecticides.
  
• Fall webworm tents are beginning to appear, but they are virtually unnoticeable right now unless sought out. This pest slowly extends its silken web from the branch tips down the branch to eventually cover entire branches with its often large and unsightly web. This pest is generally thought of as being only an aesthetic pest. If necessary, treat with a pyrethroid insecticide or with a product that contains spinosad.

Hymenoptera:

• Introduced pine sawfly is active. It is not as common in the state as is European pine sawfly and the redheaded pine sawfly, but it has the potential to be every bit as destructive. It tends to be more prevalent in the eastern portion of the state than in central or western Massachusetts. Treat the very young larvae with an insecticidal soap spray and larvae of all ages with a product that contains spinosad or with one of the registered pyrethroid insecticides.
  
• Redheaded pine sawfly will appear in late July or early August and can be active well into September or later if temperatures remain mild.
  
• Birch sawfly caterpillar remains active. Although it attacks many birch species, river birch can be a common host plant. There exists more than one species of what is commonly called birch sawfly. However, their feeding, damage, and controls are all very similar. Monitor birches for clusters of sawfly caterpillars hugging the margins of foliage. Typical to most sawfly caterpillars, they will curl their abdomens and writhe when disturbed. Treat the very young larvae with an insecticidal soap; spray the older larvae with a product that contains spinosad or with one of the registered pyrethroid insecticides that is labeled for this pest.

Coleoptera:

• The next generation of lily leaf beetle , a red beetle, is now prevalent. Eggs have been found on leaf undersides, and these will be hatching soon. Certain pyrethroid insecticides are effective against the adults as well as the larvae, while products that contain spinosad are very effective for the larvae.
  
• Viburnum leaf beetle adults are active and laying eggs. However, the bulk of this year’s damage has already occurred. This pest still remains rather uncommon in Massachusetts. 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
  
• Imported willow leaf beetle remains active, and its injury is becoming obvious. As an adult, this pest is small, rounded and a shiny bluish-black color. There are multiple generations of this pest throughout the growing season. Adult beetles chew holes in the foliage while the larvae line up on the leaf surface and severely skeletonize the leaves. By August, damaged foliage dies and turns brown on heavily infested trees and gives the tree the appearance of having been swept by fire. Larvae can be treated with a product that contains spinosad while adult beetles are better managed by a pyrethroid-type insecticide. There will be overlapping generations of larvae and adults all active at the same time throughout the season.
  
• Asiatic garden beetle adults are still commonly seen. Their feeding damage will begin to appear on a number of differing host plants as chewing injury. This pest has a very wide host plant range. It is a night feeder and hides during the day in soil and leaf litter. Occasionally, this pest is attracted to outdoor lighting. Inspect susceptible host plants at night with a flashlight. Adults are rust-colored, oval-shaped scarab beetles. They commonly feed from the time it is completely dark (around 9 PM) until about midnight. Treat with a registered pyrethroid insecticide if necessary.
  
• Japanese beetle started to be observed by late June, albeit in small numbers. It is now quite prevalent statewide, and its injury is becoming noticeable. This pest has a two month staggered emergence, which begins in late June, peaks in early August, and then tapers off into September. At first, we will only see a few adult beetles, but the number of new beetles emerging from the soil every day will continue to increase into August. This pest has a huge host plant range and can be extremely destructive. Monitor for its activity and treat when necessary. Pyrethroid knockdown sprays seem to work well against the adults. More than one application may be necessary over a two-month period in order to protect individual plants.
  
• Black vine weevil adults will become active by the end of the month.These are nocturnal and difficult to monitor visually. Common host plants in the landscape are rhododendron and taxus. Inspect lower foliage (in particular) for small hemispherical notches in the needles margins. If this is done prior to adult emergence, then a baseline can be set for gauging the level of new injury. Also, adult weevils can be monitored by placing a strip of burlap that has been loosely folded into pleats around the base of susceptible plants. Remove the burlap during the day, unfold, and inspect for weevils. Otherwise, they hide during the day in leaf litter and are difficult to find. This weevil does not fly and, therefore, walks up the plant each night to feed, which is why the foliage on the lower portions of host plants often receives greater injury. If large numbers are found, treatments may be necessary. Labeled compounds for this pest include lambda-cyhalothrin, permethrin, bifenthrin, cyfluthrin, others.

Piercing-Sucking Pests:

• Many spider mite species are now reaching large numbers. 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. One of the cool-season mites, spruce spider mite, is now going dormant for the summer, but it will return to the host plants in late August–early September and has the potential to feed well into the fall, especially if the weather remains mild. Monitor spruces and hemlock by shaking branches over a white sheet of paper and inspecting with a hand lens. Now that hot temperatures are more of the norm, many predatory mite species will leave the host plant and seek protected shelter in leaf litter and other places. During this time, they may not feed at all thus greatly reducing the natural pressure on spider mite populations. Given that spider mites reproduce so prolifically and that hot weather accelerates their developmental time, populations of spider mites can suddenly explode into large and damaging numbers.
  
• Many aphid species remain very active. Certain early-season feeders, such as snowball aphid on many different species of viburnum, are now mostly finished for the year. However, those other species that are found on various species of maples (including Japanese maple), catalpa, linden and other deciduous hosts, are still quite active. Balsam twig aphid has finished feeding for this year. 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.
  
• Hemlock Woolly Adelgid is now dormant for the rest of the growing season. It will remain on stems at the base of needles in the nymphal stage. It can still be treated with horticultural oil at the summer rate, but the weather must be watched closely. Most manufacturers of oils recommend that oils not be applied when daily temperatures are above 85 or 90 degrees Fahrenheit. Imidacloprid as a soil injection or trunk injection can be administered starting in mid to late August. This pest will emerge from dormancy around mid October and resume feeding and development.
  
• All species of lacebugs are active. Such hosts as Japanese andromeda, azalea, rhododendron, cotoneaster, hawthorn, and others should be monitored for any lacebug injury. Insecticidal soap sprays or horticultural oils at the summer rate can be effective when targeted to the undersides of the foliage. Systemic applications of imidacloprid can be very effective against these pests. Pyrethroids are effective as well. Susceptible plants in sunnier locations are often severely damaged by lacebugs.
  
• Sharpshooter leafhopper (aka redbanded leafhopper) will be arriving in Massachusetts very soon, if not already here. This green leafhopper with two red chevron stripes on its back does not over-winter here but arrives from more southern states about this time. It is mostly attracted to rhododendron, especially those that continue to produce new leaves into August, such as maximum and catawbiense. Leafhopper feeding and egg-laying cause this new foliage become distorted and stunted. Treat with a knockdown-type insecticide, such as a pyrethroid, if necessary.
  
• Potato leafhopper also arrives here every summer by late June. This pale-green leafhopper has a rather wide host plant range but commonly attacks maples, especially in the nursery. Heavy infestations start out by causing stippling injury, but foliage then takes on a bleached appearance from the extensive feeding of this pest. Treat with a knockdown-type insecticide, such as a pyrethroid, if necessary.

• 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 other 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 remains 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.
  
• Pine needle scale crawlers of the second generation will be active very soon. Treat with a horticultural oil spray if populations are large. Mugo and scotch pines are common hosts.
  
• Tuliptree scale is very active on tuliptree. This large scale is easily seen clustered together along smaller stems. It also produces copious amounts of honeydew, which, of course, encourages much honeydew. This is a tough pest to manage. Systemic imidacloprid is effective in reducing numbers of this pest. Oil sprays, especially for the crawlers, can help as well.
  
• Taxus mealybug, which technically is not a scale but can appear scale-like, rremains active. Inspect the branches on the interior of the plant. Just inspecting the foliage will not reveal this pest. Occasionally, it appears in large numbers and can be responsible for much honeydew, sooty mold problems, stunted growth, and chlorosis of the host plant. Systemic application of imidacloprid can be helpful. Also, horticultural oil sprays at the summer rate that are targeted to the inner branches can also be effective in controlling this pest. Do not confuse it with cottony taxus scale (aka cottony camellia scale), which also occurs on the inner branchs as well as on the foliage of Taxus.
  
• Cottony taxus scale (aka cottony camellia scale) is very active right now on taxus, in particular. Inspect inner branches and the undersides of foliage for the white, cottony, oval egg masses. Some of these egg cases may still have the dead adult female body attached thus giving one end a light brown color; these, however, eventually fall off. Newly hatched nymphs will migrate to the leaf (needle) undersides and feed with their piercing-sucking mouthparts. This pest also produces honeydew, which leads to the unsightly buildup of sooty molds. Extensive feeding can stunt plant growth and contribute to chlorosis. Treat the same as mealybugs on Taxus.
  
• White prunicola scale, in Massachusetts, is mostly seen as a pest on Japanese cherries and sometimes on lilac. A very similar species (white peach scale) can also appear on lilac but is not all that common in Massachusetts. In the field, however, both species are nearly identical. Crawlers of white prunicola scale will be active soon, and this provides the best opportunity to manage this difficult and serious pest. Heavily infested branches will appear heavily encrusted with bright white scales (males). If left untreated, this pest is quite capable of killing branches, shoots, and entire plants. Treat with a horticultural oil spray before the crawlers wax over. Another generation of crawlers will appear in early August.

Borers:

• Bronze birch borer adults have become active. They will continue to emerge from dying trees into late August and main remain active into September. Adult beetles seek a mate and a weakened birch tree. Larvae of this pest cannot survive in a healthy birch. Old birches, drought-stressed trees, and trees suffering from other problems, such as soil compaction, are most susceptible. It is recommended that birches, in general, not be pruned from this time into September. This process releases plant volatiles into the air that may attract this pest. Watering susceptible birches during times of drought goes a long way in preventing this pest. Once the larvae are inside of the tree, it becomes a difficult pest to manage. Early infestations might be controlled with systemic bidrin.
  
• Adults of dogwood borer, a clear-winged moth, are active and will remain so for a couple of months. Females seek wounds on host plants and lay their eggs nearby thus allowing easy entry into the host plant. Avoid wounding dogwoods with line trimmers and mowers. Infestations of this pest can be treated successfully with beneficial nematode sprays to the trunk and scafold branches in mid to late August.

DISEASES -

Gymnosporangium rust infections are visible as orange-yellow spots on susceptible hawthorn, apple, and crab apple leaves. In addition, there are tiny yellow-white tube-like fruiting structures extending from the underside of infected leaves. From mid summer to autumn, spores are wind-carried from the broadleaf host’s leaves and, when conditions are wet, they infect green shoots and needles of junipers. Pea-sized to 2 inches diameter round, brown galls develop on susceptible juniper needles and twigs between 12 and 20 months after infection. The best long-term approach to manage this disease is to grow Gymnosporangium rust resistant hawthorn, apple, and crab apple as well as juniper varieties. If desired, apply fungicide to protect high value eastern red cedar and other susceptible junipers from early July through early September.

Now is the time to scout rose, dogwood, sycamore, phlox, and horsechestnut, to name a few susceptible woody plants, for powdery mildew . The fungus is now visible as dusty, gray to white spots on foliage and green shoots. 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. 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 the surfaces of all susceptible plant parts to prevent infection. Spray on a regular schedule, and repeat more often during warm, humid weather.

Spotting is highly visible, but the best time to apply fungicides to protect emerging crabapple leaves from apple scab has passed for this season. It is still helpful to 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 mountain ash to grow and simplify disease management.

Continue to apply fungicide treatments to manage black spot on rose on high value roses and repeat the 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 - The United States Forest Service (USFS) reported 132 streams baited in 27 states with 248 samples collected. Two streams tested positive for Phytophthora ramorum during the water baiting survey.

Federal Regulation, State Inspection, Nursery Survey, and Other Finds - As of July 1, there have been a total of 13 positive nursery finds in the Western Region and 3 in the Eastern Region this season.

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

WEEDS -

No report this week.

DISEASES -

No report this week.

WEEDS -

No report this week.

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