Lepidoptera:

• Mimosa webworm webs are obvious 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 quite 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. Thus far, fall webworm appears to be only sporadic and in limited numbers. If necessary, treat with a pyrethroid insecticide or with a product that contains spinosad.
  
• Rose-of-Sharon caterpillar (aka hibiscus caterpillar, Anomis commoda) remains active on Rose-of-Sharon hibiscus. This introduced pest has the potential to completely defoliate this host plant when it occurs in large numbers. Where Japanese beetle tends to create a skeletonizing type of defoliation on this host plant, the Rose-of-Sharon moth caterpillar consumes leaves in their entirety. Initially, this introduced pest was prevalent on Nantucket and then the coastal areas of mainland Massachusetts. Deborah Swanson of Plymouth County has been reporting its presence there for several years now. In 2006, it was noted for the first time in parts of western Massachusetts ( Amherst area). This gray caterpillar will hug the stems of the host plant closely when at rest, which is very cryptic posturing and renders it almost impossible to see when scouting. Inspect for defoliation that is not indicative of Japanese beetle. Then, inspect very slowly and meticulously for the presence of the caterpillars on the stems. Once one is found, it becomes apparent just how difficult they are to find. When this caterpillar is handled, it will thrash wildly in an attempt to escape. Treat infestations with a product that contains spinosad or with one of the registered pyrethroid insecticides. For more information about this pest, refer to the book, “Caterpillars of Eastern Forests” by Dr. David Wagner, page 371.
  
• Maple webworm is active, mostly on sugar maple. This caterpillar ties several leaves with silk, and its feeding activity shreds the foliage leaving the appearance of a fall webworm tent that was started but abandoned. Many webs may be found per tree. This insect appears sporadically and rarely, if ever, requires treatments of any kind.

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.
  
• Dogwood sawfly is active. This yellow hymenopteran caterpillar with black spots often has its body covered with a thick white pubescence. As the caterpillar rests on the foliage in a curled position, its presence resembles that of bird droppings. It consumes most of the foliage down to the mid-vein of each leaf. It is mostly common on Cornus sericea (Redosier Dogwood) and C. sericea 'Flaviramea' (Yellow Twig Dogwood) and gray dogwood but can be found feeding on others. If necessary, treat with a pyrethroid insecticide or with a product that contains spinosad.

Coleoptera:

• 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 dwindling in numbers but can still be found. 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 nearing the end of its adult activity.

Piercing-Sucking Pests:

• Many spider mites 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.
  
• 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.

• Most species of lacebugs remain active. 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 spayed 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 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.

• 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. 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.

• Pine needle scale crawlers of the second generation have now appeared. 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.

Borers:

• Shoot-killing bark beetles on white pine (there is no common name for this bark beetle). This year in much of Massachusetts and also in many areas throughout New England, especially Maine, we have been seeing white pines with randomly scattered dead tips. These “brown flags” are obvious and give the initial impression of a severe problem. This shoot-inhabiting bark beetle was first noticed about 15 years ago in Massachusetts. It was quite prevalent for a few years, but then it almost vanished until this year. Now we are seeing it statewide. Maine is also reporting more incidences of it this year as well. Massachusetts Department of Conservation and Recreation (MDCR) has keyed it out to being in the genus, Pityophthorus. However, the exact species is not known; it could possibly be LeConte. The United States Forest Service (USFS) publication, “Insects of Eastern Forests” (Publication #1426, pg. 363, December 1985) describes the genus as having more than 100 species in North America. Drought may play a role when we see larger numbers of them. Thus far, no one has had to treat for this insect. It is viewed as being an occasional curiosity.

Miscellaneous:

• Western conifer seedbug, a common house invader in the fall, is very active right now on various conifers. Although causing no injury to our conifers, it has the potential to become a serious nuisance pest in October.

• Several reports from around the state have been received recently about home invasions by millipedes. These non-insect arthropods usually only appear in homes, especially basements, during extended periods of drought. They usually prefer to stay in forested areas; but when the leaf litter becomes too dry, they seek moister environments and mistakenly enter homes. They create no harm within homes but can be a nuisance by their presence alone. If left untreated, they generally die within a week or two from the dryness. Millipedes in homes can be vacuumed and removed, if necessary.

DISEASES -

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. In addition, collect fallen leaves because fruiting structures within them is the primary way the fungus survives winter. The fruiting structures produce spores for new infections next spring. 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. It is also beneficial to remove severely infected canes and foliage. 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 and powdery mildew to reduce the maintenance needs.

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 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.

Federal Regulation, State Inspection, Nursery Survey, and Other Finds - 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.

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.

IMPORTANT INFORMATIONAL RESOURCES

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

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