UMass Extension Landscape Message #21
August 13, 2004

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ENVIRONMENTAL DATA

The following growing degree day (GDD) and precipitation data was collected from July 28 through August 11, 2004. Soil temperature and phenological indicators were observed on August 11, 2004. Accumulated GDDs represent the heating units above the 50° F. baseline temperature collected via our mini-computers since the beginning of the current growing season. Please note that this data is particularly useful for pinpointing pest development at any time during the season.

Southeast - General conditions: Pleasant summer weather continues but with very little rain. Hanson received only 0.85 inches of rain over the past two weeks and soils are very dry. Many unirrigated plants are showing signs of wilt and premature leaf drop. Many trees, like ash, oak, and red maple that were defoliated by caterpillars earlier this past spring, have not fully recovered and look poorly. Albizia julibrissin, Hydrangea paniculata , Hydrangea quercifolia (Oakleaf hydrangea), Liatris, Veronicastrum, hollyhocks, Joe-pye-weed, Rudbeckia triolbum, Rudbeckia 'Goldsturm', Echinops ritro, daylilies, Echinacea purpurea, Corydalis lutea, Nepeta, Heliopsis 'Summer Sun', Monarda didyma, Dicentra 'King of Hearts', Campanula sp., Lysimachia clethroides and Phlox paniculata are in full bloom.

East - General Conditions: Mostly dry with no prolonged heat waves.

Central - General Conditions: No report.

West - General Conditions: The conditions in the Pioneer Valley have been quite variable from cool and dry mixed with warm humid periods. Lawns continue to be green and newly seeded areas have filled in well. Gardens, trees and shrubs are also thriving. Pests/Problems: Powdery mildew is quite visible on herbaceous and woody ornamentals such as phlox, zinnia, flowering dogwood, sycamore and lilac.

Berkshire - General Conditions: High humidity, heavy morning dew, and periodic showers have dominated the weather for much of the summer and the past two weeks were no exception. Temperatures did drop to the mid-forties for several mornings, an unusual situation for early August. Adequate moisture and cool temperatures have helped keep landscapes looking lush. Pests/Problems: The weather conditions which have promoted steady plant growth have also contributed to a large number of foliar diseases on annuals and perennials in the landscape. The slug and snail population has had a devastating effect on these same plants. Japanese beetles, fall webworm, aphids, mosquitoes, deer ticks, wasps and hornets are prominent.

PHENOLOGY

The phenological indicators are a visual tool for correlating plant development with pest development. The following are the indicator plants and the stages of bloom observed for this period:

CAPE COD REGION - Roberta Clark, Horticulturist for Barnstable County, Barnstable.

SOUTHEAST REGION - Deborah Swanson, Horticulturist for UMass Extension in Plymouth County, Hanson

EAST REGION - James R. Allen, Horticulturist and Greenhouse Manager for UMass Biology Department, Boston

CENTRAL REGION - Joann Vieira, Superintendent of Horticulture, Tower Hill Botanic Garden, Boylston.

WESTERN REGION - Dan Gillman, Plant Pathologist, Urban Forestry Diagnostic Lab, UMass, Amherst.

BERKSHIRE REGION - Ronald Kujawski, Nursery Specialist, UMass Extension Agriculture & Landscape Program, Amherst.

WOODY ORNAMENTALS

INSECTS

Caterpillars

In general, products containing Bacillus thuringiensis (B.t. kurstaki) are very effective against the younger free-feeding caterpillars in the Lepidoptera only. Products that contain spinosad are generally very effective against caterpillars in the Lepidoptera and the Hymenoptera (wasp-like as adults). There are also many chemical insecticides that are labeled for caterpillars, which are pyrethroids, organo-phosphates, carbamates, and other classes.

Lepidoptera (moths):

• Gypsy Moth adults are virtually finished now.
  
• Mimosa Webworm caterpillars remain very active. The larvae tie foliage together in clumps and then skeletonize the leaflets from within these 'pads' of leaves. Look for clumps of browned leaves. Treat with a spinosad product or one of the registered chemical insecticides. In some cases, this pest can affect every leaf on honeylocust; by late summer, the trees become very unattractive.
  
• Juniper Webworm caterpillars remain active. They will tie foliage with silk and cause browning of the foliage. They will be active until the fall and then again next spring until they pupate. It is the second generation that is active now. Treat with a Bacillus thuringiensis kurstaki product or a product that contains spinosad. Chemical insecticides are also labeled for this pest. Upright junipers are oftentimes more susceptible to this pest but they will be found attacking other junipers, as well.
  
• Evidence of Pine False Webworm (Hymenoptera) and Pine Webworm (Lepidoptera) is very obvious now. Look for damaged needles and clusters of silk loaded with frass pellets. However, both of these pests should now be finished feeding for the year.
  
• Fall Webworm tents are very noticeable now. This pest has dozens of deciduous host species. The larvae feed from within the silken webs and expand the size of the tents, down the branch towards the trunk, as they feed. Injured foliage remains intact but is skeletonized and brown. The damage caused by this pest is mostly an aesthetic problem and unsightly webs may remain through the winter. Individual webs can be pruned away now and destroyed. Never burn webs while still on the tree! Treat with one of the many registered chemical insecticides or a spinosad product.
  
• Silverspotted Skipper caterpillar is active now on black locust, rose acacia, and wisteria. Inspect for foliage that is tied together with silk and that has been feed upon. Caterpillars are quite spectacular in appearance by having a large dark head with two, large yellow-eye spots. The first thoracic segment is small and red. The rest of the body is a pale greenish-yellow with faint stripes going around the body. Controls are not necessary unless the caterpillars appear in large numbers.
  
• Oak Skeletonizer injury and larvae become especially noticeable at this time of year. The tiny, yellow caterpillars can be seen hanging from long threads from oak. Larvae form a cocoon that appears as a small grain of rice. In larger populations, oak leaves will have numerous individual skeletonized 'windows' on the foliage and leaves. This pest usually does not require control.

Hymenoptera (sawflies):

• Introduced Pine Sawfly remains active and may be found on the same host plants as the European Pine Sawfly. Last year, this pest was quite prevalent in the eastern part of MA and caused much defoliation. Treat the young caterpillars with insecticidal soap or one of the products that contains spinosad. Chemical insecticides are also labeled for this pest.
  
• Birch Sawfly species remain active. They will appear in clusters on foliage of many species of birch. Treat with a spinosad product when found. Small individual clusters can be pruned away and destroyed by hand.
  
• Oak Slug Sawfly remains active. Generally, they do not require control.

Beetles

In general, products containing spinosad are effective against the larvae (at least) of many free-feeding beetle, especially the Chrysomelids (leaf beetles) species. However, there are also many chemical insecticides that are labeled for beetles, which are pyrethroids, organo-phosphates, carbamates, and other classes.

Leaf Beetles:

• Lily Leaf Beetle - This pest remains active.
  
• Viburnum Leaf Beetle - is finished for this year. Visit the following Cornell web site to become more familiar with this pest: http://www.hort.cornell.edu/vlb
  
• Imported Willow Leaf Beetle remains active. The small, round blue-black adults will chew ragged notches in the margins of foliage but it is the larvae that create the bulk of the injury. These small, black, elongate larvae are now active. They line up on the leaf surface and skeletonize. There are multiple generations per year and they will remain active until September. By August, entire trees can appear to have been swept by fire; all of the leaves will be intact but dead and brown from total skeletonizing. Treat with a spinosad product or with one of the many registered chemical insecticides.

Scarab Beetles:

• Asiatic Garden Beetle adults remain active but are nearing the end of their feeding and mating cycle. These rust-colored beetles will be active for a month, or so. The grubs of this pest cause minimal injury to turf and are usually found in poorly maintained lawns. However, the adults can appear in great numbers and feed at night between first dark (approximately 9:00 PM) until about midnight. Adults feed on many hosts including garden plants, annuals, perennials and others. Their feeding can range from notched foliage to heavy defoliation. Inspect at the feeding time with a flashlight; treat if necessary.
  
• Japanese Beetle adults are very active and prevalent now. The number of new adults emerging per day is still increasing. They are strong fliers and individual beetles may live for 2 -3 weeks. Very soon there will be large numbers of this pest actively feeding. They have a very wide host range.

See the Turf Insect section below for additional details.

• Black Vine Weevil adult beetles remain active. Adult weevils feed at night and notch the margins of foliage, mostly low on the plant. Placing loosely crumpled burlap around the base of plants can also be used as a monitoring tool. Weevils will utilize the burlap as if it were leaf litter and will hide there during daylight hours. Inspect and destroy adult beetles. Treat with a chemical insecticide when found in large numbers.

Piercing-Sucking

In general, imidacloprid applied systemically is very effective on most, with the exception of spider mites. Horticultural oil or insecticidal soap, especially against the immature stages, is usually very effective.

Lacebugs:

• Andromeda Lacebug remains very active throughout MA. Inspect the undersides of foliage for their presence. Systemic imidacloprid products work well. If contact (mechanical mode of action) pesticides, such as summer oil sprays or insecticidal soap, are utilized they need to be targeted to the foliage undersides. Japanese andromeda in sunnier growing sites will experience greater problems with this pest.
  
• Azalea Lacebug remains active. Like Andromeda Lacebug, this pest is active all summer and capable of creating much stippling (chlorosis) of the foliage. Drought conditions and sunnier growing sites tend to favor this pest.
  
• Sycamore Lacebug remains active. Although common to Sycamore, it can be especially destructive to English White Oak. Active all summer, it can lead to serious chlorosis of the host plant.

Plantbugs:

• Tarnished Plantbug is very active. This small, brown insect with pale yellow markings has a wide host plant range that includes shrubs and annuals. Its feeding can cause brown spots to appear on foliage and may even kill flower buds. It has been reported to be a problem on daylily flower buds (destroying them prior to opening). Many different chemical insecticides are labeled for the management of this sometimes destructive pest.
  
• Four-lined Plantbug remains active. Its feeding causes brown dead patches to appear on foliage that resemble disease caused by pathogens. If much spotting occurs, controls may be necessary. This insect is active for much of the summer. At first appearance it almost looks beetle-like with its dark body and yellow stripes.

Aphids:

• Assorted Aphid Species are active on many different hosts. Inspect plants carefully for building populations. Catalpa, rose, lindens and many others are common hosts for aphids. Severe sooty mold problems are beginning to appear from the copious amounts of honeydew that these insects produce. Treat with insecticidal soap sprays, an imidacloprid product, a summer oil spray or with one of the many registered chemical insecticides. Catalpa Aphid and Tuliptree Aphid, in particular, are reaching peak numbers now and can be problematic.

Adelgids:

• Hemlock Woolly Adelgid can still be treated with horticultural oil even though this pest is now dormant. The young instar nymphs have settled on the stems at the base of the needles and will not move or feed again until about mid-October. However, they can still be managed with horticultural oil sprays. To know if they are alive or not, inspect them under magnification (a microscope, if possible) and gently poke them with a sharp needle. If they are dried and brittle, then they are already dead. If they exude a small amount of liquid, then they are most likely alive and dormant. If the use of systemic imidacloprid is desired, wait until the third or fourth week in August for application or once regular rain or irrigation is available along with cooler temperatures.

Other Piercing-Sucking Insects:

• Sharpshooter Leafhopper (aka Red-banded Leafhopper) is now prevalent. Although found on various host plants, they cause injury to rhododendrons, in particular. By feeding on the newest foliage, they cause stunting and curling of the foliage. These will be active until the first good frost. Although they don't kill host plants, their feeding can reduce the aesthetic value of plants, especially those in nurseries.
  
• Spider Mites - Several growth regulator products are available that offer high levels of control; mostly for population numbers that are low to moderate in size. Most are so specific that they kill spider mites but not the beneficial predatory mites. Some even posses ovicidal (egg-killing) qualities. Horticultural oil sprays can also be very effective. Many insecticides and miticides are specifically labeled for spider mites as well.
  
• Two-spotted Spider Mite remains very active. This species has a wide host range. It is also a 'warm-season' spider mite, which means that it will remain active all season long and be very prolific once the very hot and dry season approaches. Begin to monitor now and continue monitoring throughout the growing season for increasing population numbers. Treat if numbers become too high and, especially, if predator mite population numbers are too low. Horticultural oil sprays (summer rate) can be very effective as well as the other labeled pesticides for mites. Treat only if necessary. Deciduous plants, such as winged euonymus (E. alatus), will develop very chlorotic foliage and may even drop its leaves when high populations occur.
  
• Honeylocust Spider Mite is active. In some cases foliage is becoming quite chlorotic. Inspect the undersides of affected foliage for these tiny mites and treat, if necessary.
  
• Spruce Spider Mite is dormant but will return in about another month.

Leafminers

• Arborvitae Leafminer are mining foliage now. Browning of mined foliage will not appear until January or February.
  
• Locust Leafminer on Black Locust continues to be very active and its injury is now noticeable. Adults skeletonize the foliage while the larvae mine it. The next generation of adult beetles are active and mating now. Treat with a spinosad product or with one of the registered chemical insecticides to break the cycle of re-infestation. In many cases, untreated trees are beginning to appear 'fire-swept' with bronzed leaves.

Scale Insects

In general, horticultural oil sprays work well against most armored scale species, especially when they are in the crawler stage. Imidacloprid™ does not work well on armored scales but is much more effective against many soft scales.

Armored (hard) Scales:

• Monitor for Pine Needle Scale on mugo and Scots pines, in particular.
  
• Monitor junipers for Juniper Scale.
  
• Monitor different euonymus for the Euonymus Scale.

Continue to monitor scale species at the appropriate time of the season for crawlers and treat again at that time, if necessary. Inspect plants now for the crawlers of Euonymus Scale and White Prunicola Scale.

Soft Scales:

• Monitor yews and certain hollies for the Cottony Camellia Scale (aka: Cottony Taxus Scale). Treat the active nymphs with a summer oil spray. This pest creates much honeydew that generates much sooty mold. We have received many reports about this pest, this year, from central and southern CT especially. Coastal areas of MA are also experiencing injury from this pest.
  
• Monitor azaleas for the Azalea Bark Scale. Inspect inner branches for nymphs and sooty mold. Treat with a summer oil spray if necessary.
  
• Taxus Mealybug (technically not a scale but a close relative) can be found actively feeding on the inner branches of Taxus. This pest also is responsible for much sooty mold. In high numbers, it can seriously stunt plant growth. Move foliage aside to inspect the inner branches.

Gall Formers

• Maple Gouty Vein Gall has been rather widely reported this year. Sugar and red maples are the primary hosts (mostly sugar). This tiny fly (a midge) attacks foliage as it is emerging and stimulates gall formation along the main veins of the leaf; usually on the undersides. These galls are initially green but may turn red as they mature. In some cases there are so many galls per leaf that foliage becomes stunted and distorted. However, the injury is aesthetic. There are no controls nor are they necessary.

Wood Attackers

• White-Spotted Pine Sawyer adult beetles remains active. This species is only attracted to previously weakened pines and is not considered to be a pest. However, it looks very much like the Asian Long-Horned Beetle (ALB), which is not yet known to exist in MA. The adults of ALB are a very shiny black with crisp white spots. Their antennal segments alternate between white and black segments. The WSPS also has the same type of antennae. But, its body coloration is more of a dull grey and has a varying number of dull white spots. Visit the web site listed here for more details: http://www.na.fs.fed.us/spfo/alb (the main Forest Service page for ALB). Under the heading for Information, select publications; then open the link to the fact sheet titled "Asian Longhorned Beetle vs. Whitespotted Sawyer."
  
• Monitor previously stressed plants (drought, soil compaction, etc.) for signs of invasion of wood borers. Bronze Birch Borer is one such invader. Water infested trees during drought periods. Insecticide injections may be effective in some cases. The adults of BBB are seeking new host plants for egg-laying. Even though they only emerge over a few weeks time, the adults can remain active through August. It is recommended that susceptible birches not be pruned during this time, especially if they have been previously weakened. Pruning (wounding) releases plant chemicals that attract BBB females. The Two-lined Chestnut Borer, which is a close relative of the BBB, is also very active in previously stressed oaks and birches. Inspect for declining health and 'D'-shaped exit holes.
  
• Conifer Bark Beetles, such as the Black Turpentine Beetle invade stressed trees. Inspect for pitch tubes and streaks of pitch on the bark. These are signs of an already weak tree. Water during times of drought.
  
• Dogwood Borer - Continue to monitor for new infestations (adults are active) and continue to avoid any wounding of the tree trunks with mowing equipment and string trimmers, which encourages infestations of this pest. If necessary, monitor for adult emergence with pheromone traps.
  
• The Rhododendron Borer larvae tunnel the woody stems of plants, expelling sawdust in the process. The holes and sawdust is sometimes hidden due to dense foliage. Often, infestation is not noticed until much later in the summer when individual shoots wilt and suddenly die. Adults can be treated with a chemical insecticide. New tunnels, if found, can be treated with beneficial nematode sprays.

Nuisance Pests

• Many wasp, bee and hornet species [Hymenoptera] are increasing in numbers. Be aware of their potential presence, especially when around plant material, in order to avoid their stings.
  
• Western Conifer Seedbug populations are building and can be found on the seeds (cones) of conifers. These do not harm conifers in the Northeast. However, as populations build, the adults become a nuisance in late autumn as they seek shelter in homes. Inspect all screening now on windows, doors and attic vents. Repair, if necessary. Also, inspect and repair caulking around the same areas.

Reported by Robert Childs, Entomologist, UMass Extension Landscape, Nursery and Urban Forestry Program, Amherst

DISEASES

Horsechestnut (Guignardia) leaf blotch - scattered, irregular-shaped orange-brown blotches are visible on infected leaves. They are primarily affecting lower and inside leaves. As the summer progresses, the impact of the disease is becoming more noticeable; it is too late for chemical intervention this season. Collect and dispose of leaves as they fall.

Powdery mildews - These fungi are now visible as a dusty, gray-to-white coating on phlox, dogwood, sycamore and rose leaves, to name a few. In addition to having this dusty coating, infected immature leaves become yellowed, puckered and stunted. Powdery mildews grow superficially over both leaf surfaces as well as green shoots. 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 (cleistothecia) will be visible with a hand lens on the underside of leaves in the dusty, gray mycelia. If control is desired, apply fungicide sprays at intervals specified on the label when the white dusty spots first appear in late spring next year. Fungicides labeled to protect foliage on susceptible plants are listed in the UMass Extension Management Guide for Woody Ornamentals.

Black spot on rose - Black spot can be ugly and destructive to highly susceptible roses. Black, rounded spots are developing on infected leaves and rose hips. Infected first year canes have lesions that are reddish colored initially and then turn black. Black, pin-head sized fruiting structures develop in the center of the spots. Repeated black spot infection cycles will occur during wet periods throughout the remainder of the growing season. Eventually, spotted leaves turn yellow and drop off prematurely. Plants that sustain considerable leaf loss fail to thrive and are more prone to winter damage. Prune and destroy all infected leaves and canes. Avoid wetting foliage during irrigation. If overhead irrigation cannot be avoided, water before mid day to reduce period of time leaves are wet. Many beautiful, resistant varieties are available. Apply fungicide sprays at intervals specified on the label to protect healthy foliage. Nothing can be done to dis-infect spotted leaves. Fungicides labeled to protect foliage on susceptible plants are listed in the UMass Extension Management Guide for Woody Ornamentals.

Gymnosporangium rust (several different species of the fungus) is visible as red-orange-yellow, blister-like spots on susceptible hawthorn, apple and crab apple leaves. By mid-summer tiny yellow-white tubes will extend from the underside of infected leaves. From mid-summer to autumn, spores are wind-carried from the broadleaf host leaves; and when conditions are wet, they infect green shoots and needles of junipers. Pea-sized to two inches diameter brown galls, as well as fissures in the bark develop on susceptible juniper needles and twigs between twelve and twenty months after infection. The best long-term approach to manage this disease is to grow Gymnosporangium rust-resistant apple, hawthorn and juniper cultivars. Also, prune dormant galls on junipers infected with the cedar-apple form of Gymnosporangium rust during the summer, fall, winter and early spring (before orange jelly-like horns form). The time to apply fungicides to protect high value apples from cedar-apple rust has passed for this season. Fungicide protection of susceptible junipers is of little benefit; but if it were desired, it would be from mid-August through September.

The minute red-purple spots of hawthorn (Entomosporium) leaf spot are visible on leaves and causing some yellowing and defoliation of susceptible hawthorn. Now that the fungus is established, it regularly produces spores; and with recurring wet periods the disease spreads via these secondary infection cycles. A long-term management strategy to consider is replacement of susceptible hawthorns with resistant trees. Otherwise, preventative fungicides must be applied as buds open or when the first rains begin after the leaves start to develop in the spring; these should be repeated at labeled intervals several times until early summer. It is too late to apply chemical controls this late in the season.

Apple scab lesions are visible on susceptible crab apple leaves. Many leaves are curling or cupping where lesions developed before the leaves were mature and the dead leaf tissue constricted leaf expansion. Within weeks after infection the olive green fruiting bodies produce new spores. New infections can occur essentially the entire growing season during wet and mild conditions. Fungicide protection at this point in the season is of little benefit. Prune to increase sunlight penetration and air circulation, which promotes rapid drying of wet foliage. If apple scab is a chronic problem and replacement is an option, consider planting a resistant variety of crabapple near the susceptible one. Once the replacement tree is well established, the susceptible tree can be removed.

Dogwood anthracnose infections are evident on susceptible flowering dogwood (and even some resistant Kousa dogwood). Infected trees have scattered leaves exhibiting irregularly shaped gray-brown areas with purplish-brown margins. This can be a difficult disease to control due to the abundance of inoculum that over-winters on twigs and fallen leaves. In addition, heat and water stressed dogwood sustain more extensive branch dieback than those trees that have more vigor. If this is a recurring problem, consider replacing the tree with a resistant tree. On susceptible specimen trees consider a late summer fungicide application to protect the new flower buds from infection if the weather is cool and wet.

Sudden Oak Death (SOD) - The fungus Phytophthora ramorum causes SOD. It is a severe disease of oak and tanoak in certain Pacific Northwest fog forest areas. In March 2004 Phytophthora ramorum was found in two large ornamental nurseries in southern California. This detection demonstrates that the pathogen is not necessarily limited to the moist coastal regions of northern California and southern Oregon. At least one of the two nurseries distributes nursery stock nationwide, including Massachusetts.

There were recent discoveries of P. ramorum in commercial nurseries not associated with plants shipped from the initially positive Los Angles County wholesalers in the states of Oregon and Washington. More than 950 facilities received 844,000 plants.

Canada has identified three infested nurseries in British Columbia; one of which is a production nursery that shipped potentially infected plants to nineteen nurseries in CA, OR and WA. Program staff has sent a list of nurseries that received plants from the British Columbia nursery to the affected states.

This pathogen has a wide range of host plants, including rhododendron, viburnum and camellia, which are potential 'carriers' of the fungus when plants are transported. The damage on non-oak hosts involves minor leaf spotting and twig dieback. However, infections on these non-oak hosts may contribute to a rapid build-up of the fungus in an area, therefore serving as a reservoir of inoculum. All of the details of how the fungus spreads have not been worked out, but these reservoir plants may play an important role.

SOD (Phytophthora ramorum) surveys in nurseries and forest areas around the state are well underway. Agencies involved include the Massachusetts Department of Agricultural Resources (MDAR), Massachusetts Department of Conservation and Recreation (MDCR), and USDA Animal and Plant Health Inspection Service (APHIS) with UMass Amherst providing the lab and staff to perform the assays. To date, Phytophthora ramorum has not been found in Massachusetts, but nearby states in which it has been positively identified include Pennsylvania (indoors), New York and New Jersey.

Trace forward and national surveys continue as APHIS PPQ determines the distribution of P. ramorum. The total number of confirmed positive locales from the trace forward, national, and other survey finds is 155 in 21 States. The breakdown per State is: AL (3), AR (1), AZ (1), CA (53), CO (1), FL (6), GA (18), LA (5), MD (2), NC (9), NJ (1), NM (1), NY (1), OK (1), OR (10), PA (indoor), SC (3), TN (2), TX (10), VA (2) and WA (24). It is important to note that only three are from residential landscape situations, two in Georgia and one in South Carolina.

As of August 5, 2004, the participating states have surveyed 1,733 sites and have collected 35,150 samples; 19 sites are confirmed positives. The US Forest Service P. ramorum nursery perimeter and general forest surveys continue; all sampling results are negative to date. As of July 22, the US Forest Service has conducted 26 nursery perimeter and 13 general forest surveys.

On July 2 APHIS Plant Protection and Quarantine (PPQ) confirmed the presence of Phytophthora ramorum in Nassau County, NY. A joint PPQ, US Forest Service, NY Department of Agriculture team collected sample in the county after PPQ received information from a member of the public. The team collected the positive sample from a mature red oak tree located in a 192 acre forested county park. Further surveys are underway to identify other possible infected plants and infested sites. PPQ is currently working on determining the most appropriate regulatory response to the find.

Special note: As in any widespread survey such as this one, sometimes there are differences of opinion about the results. An example in our area is the possible find of Phytophthora ramorum in Nassau County, NY on July 2. This was discussed in Cornell Extension's Branching Out Newsletter from July 16, 2004.

Sudden Oak Death in New York? - News of discovery of the sudden oak death pathogen, Phytophthora ramorum, in Nassau County spread quickly last week and with every ounce of fact, there seemed to be a pound of fiction to accompany it. Here's what we know. Three of 44 bark samples submitted to the Cornell Plant Disease Diagnostic Laboratory in May by a private citizen were tentatively identified as P. ramorum. An intensive survey of the suspect areas by state and federal officials failed to confirm presence of the pathogen except at a site on Long Island in Nassau County where another positive sample was taken. The second sample was from red oak whereas the first one from the same site was from black birch, and the original black birch tested negative when resampled during the follow-up surveys. All diagnoses have been based solely on analysis of fungus DNA extracted from the bark of the trees; no one has successfully cultured the pathogen from samples in New York despite numerous attempts.

The technology on which the diagnoses are based is relatively new, and it is so sensitive that even the smallest bit of contamination can lead to a false reading. Furthermore, some healthy plant species and some other species of Phytophthora seem to react with a weakly positive reading in the test. This suggests that there are other chemicals in natural systems that are close enough in structure to the P. ramorum extracts to cause some organisms to test positive for the pathogen when it really isn't there. Thus, there is some justifiable skepticism about the New York discoveries, and work continues in an effort to clarify what is now a confusing picture.

For more information about SOD and Phytophthora ramorum check out the Massachusetts Introduced Pests Outreach Project web site at www.massnrc.org/pests/ . From the home page, hit the Search for Pest Info button; then enter the keywords 'sudden oak death' in the search box. Follow the link to the fact sheet.

Landscape, Nursery, and Urban Forestry Diagnostic Lab Report

The following are some of the interesting disease/abiotic disorder samples received at the UMass Extension Landscape, Nursery, and Urban Forestry Diagnostic Lab in Amherst during the period July 26 through August 6, 2004:

• Spruce - there was scattered branch tip dieback last year and more so this year on a well established tree; Sirococcus shoot blight.
• Flowering dogwood - upper leaves on the tree have extensive leaf spotting with many lower and inside leaves having gray blotches; dogwood anthracnose.
• Hornbeam - dieback of a few scattered small branches in a 10-12 year old tree; water shortage, compacted soil, heat stress/secondary coral spot Nectria canker.
• Crabapple 'Spring Snow' - extensive blight of newest foliage of trees growing in nursery field; bacterial fire blight (Erwinia amylovora).
• Cornus alternifolia - newly transplanted shrubs in a landscape with small, round, gray spots with purple margins; Septoria leaf spot.
• Kwanzan cherry - all of the leaves wilted and died on several branches of a 15-year-old tree; winter damage, splitting branch crotches, sunscald/opportunistic Leucostoma.

Reported by Dan Gillman, Plant Pathologist, based in the Urban Forestry Diagnostic Lab at UMass, Amherst, Mass

TURFGRASS

Diseases:

Rust is widespread in lawns at this time. This disease is caused by a fungus that needs water on leaf blades and prefers soft, succulent leaf tissue that is produced after heavy fertilization. However, good water and nitrogen also help the grass to grow faster, in which case the leaf blades are usually mowed off before rust can develop. That means that rust is more common where the infected leaf blades don't get mowed off such as compacted areas, low nitrogen turf, and droughty turf. Rub a white tissue or piece of fabric across a rusty lawn, and you will see the powdery orange spores. Luckily, this disease rarely kills plants, and the fungus is not toxic. At this time of year the easiest solution is to get the grass growing, so the rusty leaves will be mowed away.

The disease is also common when leaf blades are green, but the top growth has stopped in the fall. Again, we are lucky in New England because most of the spores will die over the winter, and the turf will grow back healthy and rust-free in the spring. There are resistant cultivars of perennial ryegrass and Kentucky bluegrass. See the National Turfgrass Evaluation Program website for information: http://www.ntep.org .

Gail Schumann, UMass Professor Emerita and Turf Pathologist.

Insects:

More Confusion with Grubs - In recent updates, I have tried to describe the management options as I see them for white grubs in turf. The confusion arises when we are reminded that we have readers from all over the U.S. and Canada. Of course, the pesticide regulations vary widely from one state or province to another. Further confusion arises for people dealing with mixed populations of white grubs.

Here is an attempt to further clarify some of the points I have been making over the past two or three months.

The number of turf insecticides labeled for use against white grubs is declining steadily. By the end of 2004, we will functionally be down to four or five standard insecticides in the United StatesCfewer than that in states or jurisdictions that have further restrictions. The active ingredients most often used for grubs in New England right now include halofenozide (Mach 2™), imidacloprid (Merit™), and trichlorfon (Dylox™). The first two are relatively slow acting and are most commonly used in preventive applications. (In some field trials halofenozide shows some curative activity against some species of white grubs, particularly when an application is made just as the young grubs are molting from the first instar to the second instar. In general, it appears to be a bit more consistent when applied just as eggs are hatching.) Dylox™, of course, is a very fast acting but short-lived product. (Note, again, that Dylox™ is on the list of products that cannot be used on school grounds in Massachusetts.)

In addition, some turf managers in some states still have access to bendiocarb (Turcam™) or isofenphos (Oftanol™); functionally those products are already gone. While the label is being supported through the end of 2004 in several states, product availability is very limited. Similarly, diazinon is being phased out of use around homes and will not be available after 2004. Finally, as mentioned in a recent posting, some formulations of carbarly (Sevin™) are also labeled for grubs. Our experience has been that carbaryl is very inconsistent. But when it works, it works reasonably quickly (usually within five to seven days after application).

Different species of white grubs respond to insecticide applications very differently:

• Oriental beetles are much less vulnerable to halofenozide than are other species of grubs. In general, Oriental beetles are less sensitive to many turf insecticides but the trend is most noticeable with halofenozide.
  
• Japanese beetles are the easiest of the four New England species to control and are quite vulnerable to halofenozide, imidacloprid, and trichlorfon. As long as the timing of the application is appropriate and the material is watered in, turf managers should achieve very acceptable levels of control.
  
• European chafers fall somewhere in between. Field trials using imidacloprid or halofenozide against European chafers have provided a wide range of results. In field trials conducted in Massachusetts the level of control has ranged from less than 20% (usually with applications that were made in May or June) to nearly 100% control with both products, at one time or another. In general imidacloprid provides slightly higher levels of control than does halofenozide against European chafers, but these differences usually are not statistically significant. One of the keys to achieving good control of European chafer grubs is to remember that the chafer life cycle is about two weeks earlier than the life cycle for Japanese beetles. The "application window" for halofenozide or imidacloprid is probably a bit shorter than the manufacturers tend to suggest, and the application must be watered in.

In any case, some of the text in an earlier message implied that halofenozide was not very active against European chafer grubs. In fact, if the material is applied at the right time and watered in, it can indeed provide very acceptable levels of control. To be absolutely thorough, I was in error when I wrote that my colleague, Steve Alm (URI) reported that halofenozide was not effective against European chafers. In a recent phone conversation, he pointed out that he has never made that observation. He (along with several other turf entomologists) has noted that halofenozide normally does not work on Oriental beetles. This is yet another example of why it is absolutely critical to identify the species of grub before making any management decisions.

• Asiatic garden beetles are still more of a curiosity than anything else in New England, but their numbers appear to be increasing in some areas, particularly in unirrigated or poorly maintained turf settings. They are essentially untouched by imidacloprid - which may be why their numbers are increasing.

Note that the application window has probably already closed for imidacloprid against European chafers in southern New England, and it will be closed very soon for the other species as well. As always, grubs develop more slowly in northern New England, so imidacloprid applications can be made a little later in the summer.

Pat Vittum, Professor and Extension Entomologist, UMass, Amherst, Mass.

Weeds: No report. Visit the Landscape Message archive for previous messages.

IMPORTANT INFORMATIONAL RESOURCES

Two UMass Extension Web Sites are specially designed to provide Green Industry professionals with resources, upcoming educational programs and events, and other relevant information. The Internet address for the Landscape, Nursery, and Urban Forestry Program is http://www.umassgreeninfo.org. The Turf Program address is http://www.umassturf.org .

UMass Extension’s Management Guide for Woody Ornamentals is NOW available! Remember to use the Professional Management Guide for Insects, Diseases and Weeds of Trees and Shrubs in New England 2003-2004 as a reference tool along with this message. The guide is a 130-page guide to provide arborists, tree wardens, and green industry professionals with current information on the materials and products available to manage pests of woody plants in New England, updated every two years by the University of Massachusetts Extension's Landscape, Nursery and Urban Forestry Program. Send orders (checks payable to UMass) to UMass Extension Bookstore, Draper Hall, 40 Campus Center Way, Amherst, MA 01003. You can also order with a credit card by calling the Extension Bookstore at 413-545-2717. The cost is $26 (plus $5 shipping) for Part I: Professional Management Guide for Insects, Diseases, and Weeds of Trees and Shrubs in New England; $12 (plus $5 shipping)for Part II: Strategies for Plant Health Management of Woody Ornamentals; or $40 (plus $5 shipping) for both Parts I and II and the inscribed 3-ring binder to hold them. For more details or to order online, go to the Publications Section of this web site.

UMass Extension’s Turf Management Guide and IPM Facts: For more information about the pests mentioned in this message, you will need to refer to the following publications: the Professional Guide for IPM in Turf for Massachusetts, 2003-2004 edition and Turf IPM Facts . Call (413) 545-2717 to order these publications from the UMASS Extension Bookstore.

DIAGNOSTIC SERVICES

UMass Laboratory Diagnoses for Turf and Landscape Problems: Accurate diagnosis for a turf or landscape problem can often eliminate or reduce the need for pesticide use. The UMass Extension Urban Forestry Diagnostic Laboratory is available to serve commercial landscape contractors, turf managers, arborists, nurseries, and other green industry professionals. It provides woody plant disease analysis, woody plant and turf insect identification, turfgrass identification, landscape and turf weed identification and offers a report of pest management strategies that are research based, economically sound, and environmentally appropriate for the situation. Send specimens and payment made payable to the University of Massachusetts to Urban Forestry Diagnostic Lab, 160 Holdsworth Way, Holdsworth Natural Resources Center, UMass, Amherst, MA 01003. The fee for a woody plant disease analysis is $50.00. All insect, weed, and turfgrass identification samples are $25.00 each. For complete information and instructions on how to send specimens, visit the Urban Forestry Diagnostic Lab page.

Turfgrass disease samples should be directed to the UMass Turf Disease Diagnostic Lab . This service is available ONLY to green industry professionals such as landscapers, lawn care companies, and golf course managers. For more info specifically on turf disease diagnostics, visit the Disease Diagnostics page at www.umassturf.org .

NEXT UPDATE: The next issue will be available on Friday August 27, 2004.

This message is produced by the UMASS Extension, Landscape, Nursery and Urban Forestry Program. The copy is prepared by Anna Greene from data and reports provided by the staff and faculty of the UMass Landscape, Nursery and Urban Forestry Program and the UMASS Extension Turfgrass Program as well as cooperating horticultural, green industry, and other professionals from the field. The text is adapted for access via the Internet by Jason Lanier and made available to subscribers via electronic transmittal by Ellen Weeks.

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