UMass Extension Landscape Message #19
July 16, 2004

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ENVIRONMENTAL DATA

The following growing degree day (GDD) and precipitation data was collected from June 30 through July 14, 2004. Soil temperature and phenological indicators were observed on July 14, 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: Sunny, humid weather the week of July 4th, gave way to cool (60s), damp weather the past week. Hanson received 1.65 inches of much needed rain. Prior to the cooler weather and rain this past week, plants in many areas of the county were wilting. Soils are moist. Hydrangea paniculata 'Praecox' (Panicle hydrangea), Hydrangea quercifolia (Oakleaf hydrangea), Hydrangea macrophylla 'Blue Billows', hollyhocks, Yucca filamentosa, daylilies, Corydalis lutea, Shasta daisy, Nepeta, Heliopsis 'Summer Sun', Monarda didyma, Filipendula venusta, Dicentra 'King of Hearts and Campanula sp. are in full bloom. Lysimachia clethroides and Phlox paniculata are beginning bloom. Southern catalpa, mimosa and Astilbe are ending bloom. Pests/Problems: Oriental, Asiatic, and Japanese beetles are active. Red lily leaf beetles, eggs and larvae are present on true lilies. Colorado potato beetle adults and larvae are feeding on Datura, Brugmansia, and Nicotiana. The barberry looper, a black caterpillar with yellow stripes, was observed feeding on barberry. Oak branches, 1-2 feet long, are turning brown and either hanging from the tree or falling to the ground probably caused by the oak twig pruner or oak twig girdler. Four-lined plant bug, slugs, snails, ticks, and mosquitoes, are all active. The UMass Diagnostic lab confirmed a diagnosis of dogwood anthracnose on a Kousa dogwood sample sent from Hanson. This the first time in 33 years that I have ever seen dogwood anthracnose on Cornus kousa. Dogwood anthracnose was also confirmed on Cornus florida (flowering dogwood). Powdery mildew is active on Phlox paniculata, Pulmonaria, lilac and rose.

East - General Conditions: No report.

Central - General Conditions: No report.

West - General Conditions: The weather has been generally cool and dry, but with 3-4 rainy episodes that supplied enough rain to keep things watered. Lawns continue to look green and trees, shrubs and gardens are lush. Pests/Problems: Powdery mildew is evident as curling, gray-colored leaves on dogwood, sycamore, oak, lilac and a number of herbaceous plants. In addition some of the leaf spot diseases are causing some premature yellowing and defoliation crabapple, hawthorn, cherry, and dogwood to name a few. A Kousa dogwood sample came into the lab with spots and blotches on the leaves. It turned out to have dogwood anthracnose. Kousa dogwood is resistant to dogwood anthracnose, but when there is inoculum, wet weather and young foliage some spotting will occur. It is still usually much less spotted and shoots are not blighted, as is the case with more susceptible dogwoods.

Berkshire - General Conditions: Soil moisture is good. Landscapes remain lush and generally in very good condition with minimal aesthetic deterioration due to pest and disease damage. Pests/Problems: The first Japanese beetles were observed last week. Slug population remains high. Powdery mildew observed on certain herbaceous perennials.

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 caterpillars have pupated. Moths will be seen soon. However, adult gypsy moth do not feed and no more injury will be caused by this pest this year. No controls are viable or necessary for the adult moths. Commercially available traps do nothing to reduce population size.
  
• Mimosa Webworm caterpillars are very active. The larvae start feeding by tying foliage together in clumps and then skeletonizing 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 and by late summer, the trees become very unattractive.
  
• Juniper Webworm caterpillars are active again. 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 subsp. 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.

Hymenoptera (sawflies):

• Introduced Pine Sawfly is 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.
  
• Mountain Ash Sawfly is mostly now finished feeding.

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 - Adults of this bright red beetle are out again. However, some larvae are quite large and still feeding. As larvae feed, they pile their own excrement on their backs thus giving them a very unattractive appearance. Monitor for their appearance on true lilies, fritillaria, and Solomon seal. Recent feedback from pest control practitioners suggests that NEEM products may not achieve the desired results for management of this pest. Spinosad products and many different chemical insecticides are labeled for this pest.
  
• Viburnum Leaf Beetle - has finally been found in MA in the town of Great Barrington (Berkshire County) not far from the NY border. Larvae have pupated and adults are beginning to appear. Treat adult beetles with one of the registered chemical insecticides. 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 are now quite prevalent. These rust-colored beetles will be active for a month, or so. The grubs of this pest cause minimal injury to turf (usually found in poorly maintained lawns) but the adults can appear in great numbers and feed at night between first dark (approx 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. Refer to the Turf Section below for more details.

Weevils (Snout Beetles):

• Polydrusus Weevil - These small and often bright green weevils are active on a variety of deciduous host plants. They will remain active well into July. They mostly create injury by notching the margins of the foliage, often to an extreme. Treat with a chemical insecticide when found in abundance. Spinosad products might be effective.
  
• Black Vine Weevil adult beetles will begin to appear by the end of July. Inspect lower foliage of Taxus and Rhododendron now to establish a baseline for new injury. Adult weevils feed at night and notch the margins of foliage. 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 is 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 active. This small, brown insect with pale yellow markings has a wide host plant range that includes shrubs and annuals.
  
• 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. Treat with insecticidal soap sprays, an Imidacloprid product, a summer oil spray or with one of the many registered chemical insecticides.

Adelgids:

• Hemlock Woolly Adelgid can still be treated with horticultural oil but monitor plants carefully for their stage of development. This pest is about to become dormant. The young instar nymphs will settle on the stems at the base of the needles and not move or feed again until about mid-October. However, they can still be managed with horticultural oil sprays.

Other Piercing-Sucking Insects:

• 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.

Leafminers

• Arborvitae Leafminer are mining foliage. 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. 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 will appear to be fire-swept by August as all of the foliage is killed.

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.
  
• Pine Needle Scale crawlers will be emerging soon.

Continue to monitor scale species at the appropriate time of the season for crawlers and treat again at that time, if necessary.

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

Many different galls have appeared on various host plants; most are insignificant in terms of plant injury.

• Felt patch galls, caused by certain Eriophyid mites, are commonly found on maples, beech and other hosts. Although usually a tan color, they can sometimes be a spectacular pink color and raise much alarm. They are harmless.
  
• 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.
  
• Aphid-induced galls are common on certain elms. These large pouch-like galls are often very numerous. There are no controls for these nor are any deemed necessary.
  
• Galls on oaks - Mostly stimulated by Cynipid wasp species, the majority of these are harmless. However, if found on the stems, they can be quite serious. Unfortunately, there are no effective controls for the ones on stems. The vast majority of these will be found on foliage and control measures are not warranted nor effective.

Wood Attackers

• White-Spotted Pine Sawyer adult beetles remain 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.
  
• Rhododendron Borer adult moths are active. Pheromone traps are available for this clear-winged moth species. Adult females lay individual eggs usually near the base of shoots of rhododendron. Tunneling larvae will expel sawdust but this is often 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 possible to find, 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.

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, inside leaves, and less than 10% of the total leaf area. As the summer progresses, the impact of the disease may be more noticeable, but chemical intervention for this season is of little benefit.

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. 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 midday to reduce period of time leaves are wet. Many beautiful, resistant varieties are available. Apply fungicide sprays at intervals specified on the label. Fungicides labeled to protect foliage on susceptible plants are listed in the UMass Extension Management Guide for Woody Ornamentals.

Cedar-apple rust is visible as 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 apple leaves; and when conditions are wet, they infect green shoots and needles of junipers. Pea-sized to 2- inch 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 cedar-apple rust resistant apple and juniper varieties. Also, prune dormant galls on juniper during the summer, fall, winter and early spring (before jelly-like horns form). Avoid growing susceptible junipers close to apples. The time to apply fungicides to protect high value apples from cedar-apple rust has passed for this spring. Fungicide protection of eastern red cedar and Rocky mountain junipers is seldom performed; 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. There is little benefit from chemical controls of this disease when they are started this late in the season.

Oak leaf blister is apparent on red and pin oak leaves as brown spots that are slightly puckered. Puckering is minimal but evident, if you look closely. This is a not a serious disease problem in our area. If a severe outbreak is occurring on specimen trees, note that for future reference. Fungicide control activities should be started just before buds open next spring.

Apple scab lesions 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 it are well established the susceptible tree can be removed and management of this disease is much easier.

Susceptible flowering dogwood have scattered leaves exhibiting irregularly shaped gray areas with purplish-brown margins of dogwood anthracnose infections. 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 variety. 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) 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, New York and New Jersey.

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.

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.

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, serving therefore 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.

As of June 15, P. ramorum has been confirmed in plants traced forward from the initially positive Los Angles County wholesaler at 118 sites in 16 states. The numbers of nurseries or garden centers with positive trace forward samples from the wholesaler by state are California (43), Alabama (3), Arkansas (1), Florida (6), Washington (11), Oregon (9), Texas (10), Colorado (1), Georgia (13), Louisiana (5), Maryland (1), North Carolina (9), New Mexico (1), South Carolina (1), Tennessee (2), and Virginia (1). The Federal confirmed nursery protocol was implemented at these facilities. One residential sample from South Carolina linked to the wholesaler has been found positive.

There were recent discoveries of P. ramorum in commercial nurseries not associated with plants shipped from the initially positive Los Angles County wholesaler in the states of Oregon and Washington. APHIS held several discussions with the affected states and stakeholders and trace forward surveys have begun at nurseries and garden centers that received stock from an Oregon production and wholesale nursery. More than 950 facilities received 844,000 plants.

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 June 28 through July 9, 2004:

• Boxwood - 4-year old hedge with several portions turning brown this spring; winter freeze and drying/worsened by secondary Volutella blight.
• Kousa dogwood - well-established tree with many one-quarter-inch circular spots and occasional large blotches; dogwood anthracnose (Discula).
• Katsuratree - large branch on a 10-year-old tree died in mid-June; Botryosphaeria canker.
• Korean maple -a tree planted last spring to replace a Japanese maple that died the year before had several upper and lateral branches that recently died; Verticillium wilt.
• Copper beech - black knob-like structures were growing out of the base of a well established tree that grew well until 3-4 years ago when it began a steady decline; Xylaria root rot.
• American elm - mature tree near a canal developed several yellow-brown branches high in its crown; Dutch elm disease.

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

TURFGRASS

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

Insects:

We are getting into the time of year when various species of white grubs are becoming active throughout southern New England. Japanese beetle adults are becoming very noticeable in many locations. Note that some of these beetles have small white spots on the thorax. These are eggs of a parasitic fly that will hatch into larvae and burrow through the exoskeleton and destroy the tissue, eventually killing the adult. Do not kill these beetles; the parasitic fly will take care of that for you!

European chafer adults have been "out and about" for at least a couple weeks and have begun to lay eggs. In addition, we saw several oriental beetle eggs in soil samples from Westchester County, just north of New York City. The samples were taken late last week (July 9). So, now is the time to review your plans for grub control. If you plan to use a slow acting product such as imidacloprid (often sold as Merit™) and your primary target is European chafers, the product should be applied very soon, preferably by July 25 in most locations in Massachusetts. If you are targeting Japanese beetles or oriental beetles, the material should be applied by 10 August. In any case, it must be watered in with at least 0.1 inch of irrigation or rain. More water is even more helpful.

Halofenozide, often sold as Mach 2™, is also a relatively slow acting product but must be in place before grubs reach their third, and largest, stage of development. Studies in several locations indicate that Mach 2™ tends to be less effective against oriental beetles and European chafers than it is against Japanese beetles. Timing of application becomes even more important. Follow the guidelines given above for Merit™, and Mach 2™ will have a reasonably good chance to reduce grub populations significantly. (Note, however, that Steve Alm, an entomologist at the University of Rhode Island, has reported that Mach 2™ is much less effective against Oriental beetles and European chafers, and he generally is not comfortable recommending it for those species. This is one of those "let the buyer beware" situations.)

A visit to the ubiquitous large general stores that abound (such as Wal-Mart and Home Depot) reveals that the shelves are full of granular insecticides with pictures of grubs on the label. Unfortunately, you must read the fine print and make wise selections. Most of the products that contain a pyrethroid as the primary active ingredient will not work against grubs because the product will be tied up in the thatch and never get to the soil. While there is a dizzying array of trade names, the active ingredients of pyrethroids include such things as permethrin, cyfluthrin, bifenthrin, lambda-cyhalothrin, and deltamethrin. So take the time to look at the fine print.

Two other granular products appear on the shelves as well that can provide control of various white grubs if used properly. Carbaryl (usually sold as Sevin™) has been inconsistent in our trials over the years, but sometimes it works very well. It takes about five days to start working, and will remain active for about four or five weeks. It should not be applied until most eggs have hatched, probably mid August for most locations.

Trichlorfon, often sold as Dylox™, is even faster acting but only lasts for seven to ten days. It should not be used until even later in the summer - late August or early September. Remember that Dylox™ is one of the products on the list that cannot be used on school grounds.

For those who want to use entomopathogenic nematodes - Studies at Rutgers University in New Jersey indicate that the currently available nematode that works on grubs (Heterorhabditis bacteriophora) is quite effective against Japanese beetles but markedly less effective against other species. In any case, nematodes should not be applied until grubs have hatched out of the eggs and are beginning to grow. Water is even more important following nematode applications than for traditional insecticide applications.

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

Weeds:

Crabgrass has grown past the point where postemergence applications may be effect. Carefully examine growth stage before application. Applications will most likely be limited to quinclorac (Drive™) at this point.

Broadleaf postemergence applications can continue as long as the turf and weeds are actively growing and are not suffering from heat or moisture stress. Heat and moisture stress may cause turf injury and poor weed control.

Randall Prostak, Weed Specialist, UMass Extension Landscape, Nursery, and Urban Forestry Program, Amherst, Mass.

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 August 2, 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.

DISCLAIMER. This message is intended for commercial use. UMASS Extension assumes no liability for recommendations. The use of trade names does not imply endorsement. Similarly, there may be other products you prefer to use.

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