UMass Extension Landscape Message #7 - 2006

Scouting Information by Region

Environmental Data

The following growing-degree-day (GDD) and precipitation data was collected for a two-week period, April 6, 2006 through April 12, 2006. Soil temperature and phenological indicators were observed on April 12, 2006. Accumulated GDDs represent the heating units above a 50° F baseline temperature collected via our instruments since the beginning of the current growing season. This information is intended for use as a guide for monitoring the developmental stages of pests in your location and planning management strategies accordingly.

Regional Notes

Cape Cod Region (Barnstable) - General Conditions: Typical spring weather for the Cape is the norm. High temperatures ranged from 36°F on 4/8 to close to 60°F on 4/12. We received some much needed rainfall over the weekend, with some sleet mixed in. Plant development is progressing nicely, with spring clean-ups well under way. Forsythia is beginning to bloom in many areas, along with Corylopsis paucifolia (buttercup winterhazel) and Rhododendron mucronulatum (Korean rhododendron). Daffodils are brightening up the roadsides. Pests/Problems: As of April 12, we have not seen larvae of the winter moth in the buds we are monitoring. Adult deer ticks are active; bees and wasps are flying; ants are beginning to forage. Indoors, western conifer seed bug is trying to exit.

Southeast Region (Hanson) - General Conditions: Hanson received 0.62 inches of rain. Cooler weather held plant growth in check, so plants are coming into flower gradually, depending on location and microclimate. Cornus mas, Pieris japonica sp., early cherry, Magnolia 'Leonard Messel', star magnolia, forsythia, Omphalodes, crocus, Helleborus niger, H. foetidus, H. x hybridus, Pieris 'Brouwer's Beauty', scilla, Vinca minor, early tulips and daffodils and Corydalis solida are in full bloom. Saucer magnolia, Pieris floribunda, Pulmonaria sp., and early violets are just starting to bloom. Pussy willow, Abeliophyllum distichum (White forsythia), and Iris reticulata are past bloom. Pests/Problems: In Hanson, winter moth caterpillar eggs have started to hatch. Hatching of winter moth probably began on Saturday, April the 8th. The caterpillars are very small, about the size of the tip of an eyelash. Many eggs have yet to open. Eastern tent caterpillars are starting to hatch in the east region. Chickweed is in bloom. Solitary bees are active. Ticks are active; conduct tick checks frequently, especially after yard cleanups.  Skunks are digging up lawns.

East Region (Boston) - General Conditions: No report.

Central Region (Boylston) - General Conditions: Lack of significant rain continues. Turf is greening up and minor bulbs are in full bloom.

Pioneer Valley Region (Amherst) - General Conditions: There was a significant warm up in the Valley during the last few days. In addition to the flowering woody plants noted, the vegetative buds are breaking open on a number of woody plants at this time. Lawns continue to green up with more daffodils breaking bud every day. Soil moisture appears to be adequate, and there is rainfall in the forecast for the next day or so. Pests/Problems: With the recent warmth and rainfall, leaf spot and shoot blight fungal spores as well as bacteria blow and splash onto nearby young leaves and flowers.

Berkshire Region (Great Barrington) - General Conditions: Soils are in workable condition with moderate levels of moisture. Pests/Problems: Deer browsing activity in home gardens and managed landscapes has increased considerably over the past two weeks.

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.
• PIONEER VALLEY - Dan Gillman, Plant Pathologist, Urban Forestry Diagnostic Lab, UMass, Amherst.
• BERKSHIRES - Ron Kujawski, Specialist, UMass Extension Landscape, Nursery & Urban Forestry Program, Amherst.

Woody Ornamentals

Insects

Warmer weather is now returning, and this will drive insect activity quickly, especially for those early season pests like winter moth. As of April 11, 2006, Deborah Swanson in Plymouth County reports that approximately 90% of winter moth eggs there are still orange. About 10% have begun to change color, which indicates that hatch should begin within days and then continue for a week or more if temperatures remain warm. Cooler locales, such as Cape Cod, will experience egg hatch later. Winter moth will be the first to appear followed by forest tent caterpillar and fall cankerworm. Gypsy moth will be next when they begin to hatch around the first week in May (during typical spring temperatures). Eastern tent caterpillar, which mostly attacks Malus and Prunus species, will hatch once the foliage of their host plants is half to fully emerged; look for the development of their silken webs in the crotches of branches.

• Winter moth - The eggs are still orange but are beginning to turn blue/black in color as they near hatching time. This exotic pest is far more prevalent than previously understood. Most of eastern MA, all of RI, some spots in southeastern NH, southeastern CT, southern NH, and certain areas along the Maine coast have this pest. The highest population numbers, by far, are in MA and RI. Once the tiny caterpillars emerge from the eggs, they will seek buds that are just beginning to swell. Winter moth caterpillars wriggle into buds and feed on both foliage and flower parts within the buds.
• Gypsy moth is expected to be in high numbers in MA, and other Northeastern states. The fungus, Entomophaga maimaiga, which controls gypsy moth naturally has not performed well during the past two springs. This is primarily a function of spring weather conditions; rainy periods at critical times during the caterpillar stage are essential for the spread of this beneficial pathogen for control of gypsy moth caterpillars. There has been some anecdotal evidence provided recently that E.maimaiga may have been more active and successful in the westernmost part of MA last year (Berkshires) than it was in the rest of southern New England.
• Eastern tent caterpillar is once again expected to be in large numbers and attacking their favored host plants of apple and cherry. Egg hatch will occur once the leaves are half to fully emerged from the buds. Look for the development of their silken webs in branch crotches.
• Forest tent caterpillar is also expected to be in large population numbers once again in MA and other surrounding states. Last year, this pest caused more than 200,000 acres of defoliation in MA. Forest tent caterpillar has been a problem in eastern MA for several years, primarily on oaks, but it is now building in serious numbers statewide, as well as in VT, on sugar maple as well.
• Fall cankerworm is expected to be in large numbers in eastern MA and on parts of Long Island, NY in 2006. Parts of RI may also experience some of this pest’s activity. Egg hatch will occur about early to mid May.
• Hemlock woolly adelgid has been actively feeding since last October and has now produced the next generation. This will be the time when the cottony masses that surround the eggs will be most visible, especially from the undersides of the branches. Make note of those plants that will require treatment with oil sprays once the correct weather conditions prevail. However, be aware of tender new foliage that will soon be emerging and delay spraying oils (at the summer rate) until after this new foliage is fully expanded and “hardened.”
• Spruce spider mite from last fall has not yet shown up yet. It will “suddenly” become apparent on those affected plants, but no mites will be seen at that time. However, make note of those plants that were inured from last fall’s feeding and expect to have more mites on those plants this spring. Once the correct weather conditions prevail, treat with an oil spray or, if eggs are present, they can be treated with one of the Mite Growth Regulators that has ovicidal activity. However, we are quickly approaching the time of year where the application of dormant oil sprays needs to be carefully considered. As plants break dormancy, they become very susceptible to the potential phytotoxic effects of dormant oils.
• White pine weevil has mostly finished its egg-laying activity for this spring, and it is now too late to treat in most regions of southern New England.
• Inkberry leafminer mines have now become obvious. Despite the larvae being in the mines since early last summer, the browning of these mines has only just occurred within the past month or two. Make note of plants with noticeable infestations and prepare to place yellow sticky cards out around early-May to monitor for the emergence of the adult flies, which will indicate the time to apply controls to break the cycle of re-infestation.
• Birch leafminer - Purchase yellow sticky cards now to place out on susceptible birches at budbreak. Adult sawflies should appear around the time that the leaves are half-emerged from the buds. Treat when the adults appear.
• European pine sawfly will become active within weeks. Take inventory now of those plants that were attacked last year by this pest. Mugo pine is the most common host here but other pines are also attacked. Treat the young larvae with insecticidal soap or a spinosad product.

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

Diseases

The rainfall has given plants a good watering, but with leaves developing, they are vulnerable to leaf spot and shoot blight infections, especially when accompanied by temperatures of 50-70 degrees F. This is the time to apply protective fungicides to nursery and specimen woody landscape plants known to be susceptible to diseases such as, apple scab on flowering crabapple, dogwood anthracnose on flowering dogwood, fire blight on mountain ash, crabapple and Callery pear, Entomosporium leaf spot on English hawthorn, Phomopsis tip blight on juniper, and black spot on rose.

In addition, scout rosaceous plants commonly infected with the fire blight bacterium, such as crabapple, apple, pear, firethorn, hawthorn, and cotoneaster. Remove dead branches and dispose of them away from the plants to reduce sources inoculum. Lilacs with dead shoots from bacterial blight also benefit from their removal. Disinfect pruning tools between each cut with 70% ethyl alcohol, a 10% bleach solution, or a comparable bacterial disinfectant.

On plum and cherry trees that are infected with black knot canker look for swollen branches (~twice the normal diameter). Prune to remove infected branches, but also to improve the branch structure within the tree crown. Removal of inoculum before the fruiting structures erupt through the bark helps reduce inoculum that could cause new infections in the spring and is a key factor in managing this disease.

Rhabdocline needle cast fruiting structures will soon be visible on infected Douglasfir needles. Symptoms of Rhabdocline infection appear as elongated red-brown spots and bands on infected needles. Spots often coalesce and most of the needle turns color except for the base, which remains green. Infection tends to occur on the bottom of the tree first. Infected needles drop prematurely from now into the summer. Spores released from these fruiting bodies during cool, wet weather infect new needles that will soon start developing. Avoid overhead watering of Douglasfir at this time of the year. Provide adequate spacing and limit weed growth around young trees. Consider fungicide applications to susceptible, high-value trees if this spring is wet. Maintain protection during the vulnerable period when the needles are first emerging from buds until they expand to full size.

Sphaeropsis (Diplodia) shoot blight on pine can cause significant damage to stressed red, pitch, Japanese black and, especially, Austrian pine in our area. If wet weather continues, new shoots developing on these trees are vulnerable to infection. Consider applying fungicides to protect susceptible trees as soon as buds swell significantly. Reapply sprays at labeled intervals until the new growth fully expands, if wet conditions persist. The Sphaeropsis fungus produces significant amount of inoculum on the outer scales of second-year cones, as well as infected shoots and needles. Prune affected shoots when plants are dry to improve appearance, but this will make little difference in reducing inoculum for new infections without cone removal, too. If replacement of severely affected pines is an option, plant trees resistant to Sphaeropsis shoot blight as well as better adapted to grow on the site.

Ramorum Blight, also known as Sudden Oak Death (SOD). Since the early 1990’s, oaks and tanoaks were dying in the coastal counties of California. Since then, other types of plants have been found to be infected or associated with this disease, referred to as Sudden Oak Death, ramorum leaf blight or ramorum dieback, or by regulation as Phytophthora ramorum. The first positive identification of the disease was in 1995 on tanoak in Mill Valley (Marin County), California. Since that time, surveys confirmed Phytophthora ramorum on various native hosts and nursery plants in several locations in California, Oregon, Washington, and British Columbia. When nursery surveys find infected plants prompt quarantine and/or eradication activities ensue. Research conducted by the Agriculture Research Service, US Forest Service, universities, and others is under way to better identify hosts, improve methods of detection, and develop effective treatments. Currently, 84 plants are regulated, two of which at the genus level (Camellia and Rhododendron). There are no chemical treatments currently available to eliminate Phytophthora ramorum from infected plants.

Status of Phytophthora ramorum Monitoring Surveys. The 2005 National Nursery Survey involved 49 states and Puerto Rico. The survey visited 3,790 nurseries and collected 68,275 samples. Overall, the survey reported 99 positive sites in 2005. The breakdown by state was: CA (55), GA (4), LA (2), OR (20), TN (1), SC (1), and WA (16).

New Hosts Added. USDA APHIS issued a Federal Order on November 15 adding Abies concolor (white fir) and Viburnum opulus (= V. trilobum) (American cranberry viburnum) to the official list of host and associated host plants. In addition, USDA APHIS issued a Federal Domestic Quarantine Order on February 10 adding Frangula purshiana (formerly listed as Rhamnus purshiana), Adiantum aleuticum, and Adiantum jordanii to the official list of P. ramorum hosts. They also identified 13 new plants as associated hosts. One of the plants, found in an infested area of California and identified by Washington State, was Abies magnifica. The other 12 new species were reported from Canada, and include: Acer davidii, Ardisia japonica, Euonymus kiautschovicus, Gaultheria shallon, Hamamelis X intermedia (H. mollis & H. japonica), Leucothoe axillaris, Magnolia grandiflora, Michelia maudiae, Michelia wilsonii, Osmanthus decorus (=Phillyrea decora; =P. vilmoriniana), Prunus lusitanica, and Rosa rugosa. The Koch’s postulate process for these plants (the process involves isolating the pathogen from the infected plant, reinfecting a healthy plant, and then reisolating the pathogen from the second plant to confirm infectivity) is not complete. Until USDA completes the Koch’s postulate process, due to uncertainty about the pathogenicity of P ramorum on these plants, these 13 new species are on the associated host list.

Dan Gillman, Plant Pathologist, based in the UMass Extension Plant Diagnostic Lab at UMass, Amherst.

Weeds

Continue the treatment of winter annuals and perennials in ornamental beds with glyphosate or glufosinate. Non-herbicide material containing clove oil, citric acid, or acetic acid can be used on small winter annuals but not on perennials. Most winter annuals are small now and can be mulched over. Perennials will need to be treated before mulching. Preemergence herbicides should be applied to ornamental beds now.

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

Landscape Turf

Diseases:

No report.

Insects:

No report.

Weeds:

Forsythia is beginning to bloom, and applications of preemergence herbicides should be in full swing. Many perennial weeds are appearing in turf but should not be treated now as control will be poor. Broadleaf herbicide applications for winter annual weeds can be done now. Prostrate knotweed can be seen in compacted and heavy traffic areas.

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