UMass Extension Landscape Message #17
June 25, 2004

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ENVIRONMENTAL DATA

The following growing degree day (GDD) and precipitation data was collected from June 17 through June 23, 2004. Soil temperature and phenological indicators were observed on June 23, 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: Summer seems to be finally be here! Hanson has received very little rain over the past few weeks and soils are dry. Clematis, landscape roses, Rosa rugosa, Viburnum dentatum, Physocarpus, Spirea, Lonicera japonica, and potentilla are in full bloom. Several perennials including Campanula sp., daylilies, Nepeta sp., Foxglove, Corydalis lutea, Thalictrum, Aruncus, and Geranium sp. are providing summer color in flower bordersPests/Problems: Asiatic garden beetles, earwigs, aphids, four-lined plantbug, polydrusus weevil, white-spotted sawyer beetle, oak sawfly, lily leaf beetles and larvae, mosquitoes, ticks, wasps and hornets are all active. Anthracnose is showing up on dogwood, maples, and sycamore. Black spot has been observed on roses. Sod webworm adult moths are active on turf. Red thread is showing up on lawns. Plymouth County Extension does not spray for mosquitoes. The number to call for Plymouth County residents is 781-585-5450.

East - General Conditions: Cloudy but dry. Pests/Problems: Willow leaf beetle adults found.

Central - General Conditions: No report.

West - General Conditions: Peonies, primroses and daylilies are rivaling the bedding plants for color in the gardens. There has been just enough rain to keep the turf and gardens growing, but the warmth and dryness are showing up as slight wilting on the late afternoons on the sunny days. Pests/Problems: Leaf spot and shoot blight (including anthracnose) diseases are evident but not as widespread this year as last year because the extended periods of rainy weather this spring were generally accompanied by upper 30° to 40° F. temperatures. That is a bit cool for the fungi to efficiently infect young leaves and green shoots. The best time to initiate protective fungicide applications to nursery and specimen woody landscape plants that are known to be susceptible to these diseases has past. The foliage on most woody plants has mature and drier weather conditions have prevailed over the last week. There is little benefit either in appearance or the health of the plants to spraying protective fungicides to control leaf spot and shoot blight diseases at this time. A disease that is just beginning to show up is powdery mildew, and this is the time to begin management. (See the Woody Ornamental Disease section below.)

Berkshire - General Conditions: It was a week of beautiful days and cool nights. A low temperature of 39° F. was recorded on the morning of June 21. Despite less than half an inch of rain, soil moisture is good. The landscape continues to flourish with colorful blooms. Pests/Problems: No report yet of Japanese beetles but they should be emerging any day now. Most defoliators except for leaf rollers and gypsy moth are gone but they left many tattered or completely devoured leaves in the wake. Iris borer damage is quite evident in the form of streaky, water-soaked iris leaves. Borers have advanced to the rhizomes. When dividing irises, care should be taken to cut away infested portions before replanting rhizomes.

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):

• Fall Cankerworm - began the process of pupation last week. It fed 10-14 days longer than winter moth and in many of the same areas. However, its feeding activity is over for this year.
  
• Eastern Tent Caterpillar - Unsightly webs remain in Prunus and Malus species but this pest is long gone for this year.
  
• Forest Tent Caterpillar (FTC) - is now pupating. Its light-colored silk cocoons can be seen on many substrates, such as tree trunks and houses. However, it will not feed again this year.
  
• Gypsy Moth caterpillars are far more prevalent this year than expected. They are being found somewhat commonly in weekly monitoring, albeit mostly in low numbers, across much of the state. In the Freetown area of Southeastern MA, their numbers are rather high and they are coming in strong on the heels of the Forest Tent Caterpillar outbreak. Gypsy moth caterpillar are mostly in fifth instar stage there and are primarily feeding on what is left of the oak leaves. They have a wider host range than that of FTC and will migrate to other deciduous hosts thus causing increased defoliation to that area this year. In areas where Forest Tent Caterpillar and/or winter moth created much defoliation, the gypsy moth may provide a double defoliation as those affected trees start to re-foliate. As gypsy moth caterpillars reach maturity, their ability to consume vast amounts of foliage per caterpillar per day increases dramatically. Products containing spinosad work very well against this pest as do the multitude of registered chemical pesticides. It is too late for the use of B.t. 'kurstaki'.
  
• Fruitworms (Green) remain and are beginning pupation.
  
• Euonymus Caterpillar remains active. This small, pale yellow lepidopteran caterpillar with black spots attacks many varieties of euonymus from shrub-form to tree-form. They produce much silk but act as free feeders by moving throughout the entire plant. Affected plants may be defoliated and covered in a fine veil of silk. Pupation is now beginning. It is most likely too late to treat now. However, if treatments are still necessary and possible, spinosad products or one of the registered chemical insecticides will be effective.
  
• The mystery caterpillar on witchhazel has now been identified. Mustard Sallow Caterpillar, Pyreferra hesperidago, [Lepidoptera] has been found in damaging numbers in certain plantings in Plymouth and Barnstable Counties. Although pupation should occur within the next one week, a product containing spinosad or one of the registered chemical insecticides may be necessary to prevent defoliation.

Hymenoptera (sawflies):

• Introduced Pine Sawfly will be active soon 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 then young caterpillars with Insecticidal Soap or one of the products that contains Spinosad.
  
• Oak Sawfly are very active. In general, they are usually found in small numbers feeding by scraping the foliage, which leads to a 'window-paning' effect. In large numbers, they can be serious defoliators. These are more prevalent this year than it has been in past years. Spinosad products are effective, if deemed necessary.
  
• Birch Sawfly are 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 should be active now. Continue to monitor for this yellow caterpillar with black spots that feeds in clusters. Small infestations can be pruned away and destroyed. Larger infestations can be treated with a spinosad product. This pest consumes all but the main vein of the host plant foliage and is capable of creating serious levels of defoliation.

Beetles

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

Leaf Beetles:

• Lily Leaf Beetle - Adults of this bright red beetle can still be found. Larvae are 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 are active now and creating much injury. Inspect viburnum for defoliation injury which should be quite noticeable now. Pupation will occur in about two more weeks. Treat with a spinosad product or 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 is 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:

• Adult Rose Chafer Adult beetles are active. Monitor roses for the presence of these tan and somewhat slender scarab beetles. Treat if necessary.
  
• Asiatic Garden Beetle are pupating and the rust-colored beetles will be active within a week or so. The grubs of this pest cause marginal injury to turf but the adults can appear in great numbers, 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. (Visit the Landscape Message Archive and refer to the Turf Insect Section of LM # 16 for additional information.)

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.
  
• Rose Curculio - This stout-bodied weevil is often a rust-red color and found on various roses. It mostly creates injury by destroying flower buds. When in large numbers, it is extremely destructive. Adults are active now. Treat with a chemical insecticide when found.

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 nymphs are active in warmer regions of 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 is 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 is 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. 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.

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.

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.
  
• Spruce Spider Mite remains active. Inspect by gently shaking branches over a piece of white paper and then inspect with a hand lens. Monitor weekly to establish if population numbers increase significantly. Note the numbers of predatory mites present. Treat if necessary.
  
• Two-spotted Spider Mite is 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.

Root & Shoot Feeders

• White Pine Weevil damage is now noticeable. The affected new terminal shoots have wilted and died.

Leafminers

• Native Holly Leafminer - There are two species of these Lepodopteran leaf-mining caterpillars in MA. Their host plants (arborvitae and some junipers, primarily), and the injury that they cause are similar. The major difference is that one species pupates earlier (i.e., two weeks ago) than the other and does so outside of the mine, usually on the underside of the foliage. Inspect for what looks like tiny and fuzzy grains of rice attached to the foliage (cocoons). Shake foliage lightly to disturb moths. When moths are found, treat with a chemical insecticide to break the cycle of re-infestation. This species tends to be more prevalent in eastern MA. The other species pupate within the mine and will emerge as an adult moth (tiny and an off-white color) during the third or fourth week of June. Treat in the same manner as the other species. Larvae, once within the foliage, are extremely difficult to manage.
  
• Locust Leafminer on Black Locust has been active for a while and its injury is starting to appear. 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 in one to two more weeks.

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.
  
• Begin to monitor azaleas for the Azalea Bark Scale. Inspect inner branches for nymphs and sooty mold. Treat with a summer oil spray if necessary.

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 are 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.
  
• 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 will be active soon. 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 at this time is not warranted for this season.

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 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 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. Fungicides labeled to protect foliage on susceptible plants are listed in the UMass Extension Management Guide for Woody Ornamentals.

Botrytis blight is noticeable as a gray moldy blight of flowers, leaves and shoots in herbaceous perennial gardens. Cool temperatures and shaded conditions enhance the damage by this fungus. To manage Botrytis blight, remove dead plant material that the fungus uses as a beachhead for the development of more inoculum. Irrigate before mid-afternoon so needles dry off before nightfall. Consider fungicide applications to protect succulent growth on high value plants from becoming infected. Fungicides labeled include: chlorothalonil, chlorothalonil plus fenarimol, copper sulfate pentahydrate, ferbam, fosetyl-Al, iprodione, mancozeb, thiophanate methyl, triflumizole, thiophanate methyl plus chlorothalonil, thiophanate methyl plus flutolanil, and PCNB. Repeat applications at labeled intervals until warm, drier weather prevails and Botrytis blight is less able to infect plants.

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" 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 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 showing up on red and pin oak leaves as faint, yellow-green spots that are beginning to turn brown. 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. Chemical control activities should be started just before buds open next spring.

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. To maintain scab-susceptible crabapples in the landscape in which infection has already occurred, consider using systemic fungicides. These fungicides act to prevent new infections that develop on newly emerging leaves. Systemic fungicide applications will not restore distorted, discolored crabapple leaves to health. They can reduce the incidence of apple scab as the season goes on if they are applied soon, before the extent of infection is too severe, and protection is maintained at labeled intervals. Alternate every second or third systemic fungicide spray with a broad-spectrum fungicide to reduce problems with fungicide resistance. 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 resistant varieties of crabapple.

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 during wet springs, apply fungicides as buds open, after bracts have fallen and again four weeks later.

The official Massachusetts Department of Agricultural Resources (MDAR), Massachusetts Department of Conservation and Recreation (MDCR), and USDA Animal and Plant Health Inspection Service (APHIS) Sudden Oak Death (SOD) survey in nurseries and forest areas around the state has begun. To date, Phytophthora ramorum has not been found in Massachusetts, but nearby states in which it has been positively identified include Pennsylvania and New Jersey.

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.

P. ramorum has been confirmed in plants traced forward from the initially positive California wholesale nursery in 97 facilities in 14 states. The numbers of nurseries or garden centers with positive P. ramorum samples from the wholesaler by state are: California (38), Alabama (1), Florida (5), Washington (6), Oregon (9), Texas (5), Colorado (1), Georgia (13), Louisiana (5), Maryland (1), North Carolina (9), New Mexico (1), Tennessee (2), and Virginia (1).

The number of confirmed positive nurseries or garden centers from the national, and other surveys is 118 in 14 states. Fourteen states continue to impose quarantine regulations over and above those ordered by PPQ on California, and in some cases Oregon, Washington or British Columbia.

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 14 through June 18, 2004:

• Douglasfir - 20-year-old tree is losing many of last year's needles and this year's needles look healthy; both Rhabdocline and Swiss needle casts.
• Colorado spruce - 7-year-old trees in a Christmas tree farm have scattered yellowing, browning and loss of many of the one and two year old needles; Rhizosphaera needle cast.
• White fir - scattered dieback of branches especially in the lower part of the tree; Leucostoma (Cytospora) canker.
• Austrian pine - new shoot and needle growth looks fine but older needles are browning from the tip inward; Ploioderma needle blight.

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:

Weeds:

Begin to monitor and treat for yellow nutsedge. Solid stands where no grass remains should be treated with glyphosate and reseeded.

Yellow woodsorrel (Oxalis stricta) or creeping woodsorrel (Oxalis corniculata) are both common in New England. Both species have yellow flowers with five petals. Yellow woodsorrel is light green in color, reproduces from seeds and rhizomes and has an upright growth habit sometimes reaching two feet tall. Creeping woodsorrel has stolons, a prostrate and creeping growth habit and usually has purple or purple-tinged leaves. The leaf color of creeping woodsorrel can vary from purple to green and should not be used solely for identification. Oxalis is often misidentified as clover, although, the leaflets of oxalis are heart-shaped whereas those of clover are round.

Interestingly enough, one night last week I spent two hours handweeding some ornamental beds. After about a half hour it dawned on me that the major weed, and in some places the only weed, was yellow woodsorrel (Oxalis stricta). There had been a few yellow woodsorrel plants last year but certainly not this many. The next morning I decide to walk around campus and look in some areas that I know had a few plants last year. As I was headed out I received a call from Deborah Swanson asking if I had noticed or heard of a lot of woodsorrel in ornamental beds or turf areas. About three minutes into my 'on-campus hunt for oxalis' I ran into Jennifer from Landscape Services and the first thing she commented on was the abundances of yellow woodsorrel compared to last year. Perhaps the very cold weather in combination with little or no snow cover effectively broke seed dormancy and resulted in a sizable flush of oxalis this spring. Regardless of the reason, areas with oxalis can be handweeded or treated with glyphosate; and if possible, a layer of mulch will help prevent additional germination. Attempt to remove plants before more oxalis seed is produced. Turf areas can be treated with a broadleaf herbicide combination containing dicamba and/or triclopyr.

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 . By special arrangement, the UMass Turfgrass Disease Diagnostic Lab is now open at Marquette University. This lab provides diagnostic services for turfgrass professionals in CT, MA, ME, NH, NY, RI, VT. 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 July 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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