Defoliators:

Lepidoptera:

• Mimosa webworm webs are obvious on honeylocust. This caterpillar ties foliage together loosely into pouches. Then, it 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 quite obvious now. 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:

• Redheaded pine sawfly will be active soon. It prefers mugo pines in Massachusetts but can be found on other pines as well. Inspect for the very visible clusters of yellow caterpillars with black spots and rust-colored head capsules. Treat with a product that contains spinosad or with one of the registered pyrethroid insecticides. Insecticidal soap sprays are also effective but mostly when the caterpillars are still quite small. This pest can feed well into October if warm conditions prevail.

Coleoptera:

• Lily leaf beetle - the next generation larvae have been feeding for two to three weeks now, statewide. 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 have ceased their activity for this year. Adult female beetles laid eggs back in July, and the pest will not resume activity until next spring. Several reports of this pest being active in very western Massachusetts (Berkshire County) were received this year. It finally looks like viburnum leaf beetle has become established in Massachusetts. Inspect for damaged foliage and, especially, for bare twigs that feel rough, like that of sandpaper; these are egg-laying sites. 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 now 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, heavily damaged foliage dies and turns brown 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 is now quite prevalent statewide, and its injury is very noticeable. This pest has a two month staggered emergence, which began in late June, peaked in early August, and is now tapering off as we approach September. 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 the two-month period in order to protect individual plants.

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. 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. 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 still dormant as it remains on stems at the base of needles in the nymphal stage. It can still be treated with horticultural oil at the summer rate, but watch the weather 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 any time now. This pest will emerge from dormancy around mid October and resume feeding and development.
  
• All species of lacebugs are extremely active now. During this current stretch of hot weather, plants are producing less defensive compounds, and lacebug development has been greatly accelerated. Also, plants tend to dramatically slow their growth during hot periods and are unable to outgrow lacebug injury as it occurs. Many susceptible plants are now severely damaged by lacebugs. The millions of individual piercing-sucking wounds have coalesced to give a plant the appearance of having been sprayed with bleach. 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) has arrived in Massachusetts. This green leafhopper with two, red chevron stripes on its back does not overwinter here but arrives from more southern states every summer. It is mostly attracted to rhododendron, especially those species that continue to produce new leaves into August, such as R. maximum and R. catawbiense. Leafhopper feeding and egg-laying cause this newest foliage to 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) - This 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. S ome 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.

• 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 sooty mold. 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, remains 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 (a.k.a. cottony camellia scale), which also occurs on the inner branches 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 build-up of sooty molds. Extensive feeding can stunt plant growth and contribute to chlorosis. Treat the same as mealybugs on Taxus.
  
• In Massachusetts, we mostly see white prunicola scale 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 provide 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.

Borers:

• Bronze birch borer adults remain active. They will continue to emerge from dying trees into late August and 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, remain 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 scaffold branches in mid to late August.

DISEASES -

Oak leaf blister is showing up on red, white, and pin oak leaves now as brittle, brown, puckered spots/blotches. 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.

Powdery mildew is showing up on susceptible rose, dogwood, sycamore, phlox, and horsechestnut, to name a few susceptible woody plants . The fungus is 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 derive sustenance from living host plants 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.

Leaf spotting, chlorosis, and premature loss are 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 mountainash 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 - As of August 1, there have been 17 positive nursery finds of Phytophthora ramorum so far. The states with these detections include California, Oregon, Washington, Florida, Georgia, and Mississippi.

Federal Regulation, State Inspection, Nursery Survey, and Other Finds - As of July 26, the United States Forest Service (USFS) reported 132 streams baited in 27 states with 437 samples collected. Two streams tested positive for Phytophthora ramorum during the water baiting survey, one in Washington and one in Mississippi.

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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