UMass Extension Landscape Message #7 - 2005

Scouting Information by Region

Environmental Data

The following growing degree day (GDD) and precipitation data was collected for the one-week period from April 7 through April 13, 2005. Soil temperature and phenological indicators were observed on April 13, 2005. Accumulated GDDs represent the heating units above the 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: This reporting period began in spring and has finished up with a return to late winter. Mild temperatures pushed plant growth over the weekend but freezing temperatures have occurred over the past two nights. Landscapes continue to green up and spring clean-ups are in full swing. Buttercup Winterhazel (Corylopsis paucifolia) and daffodils brighten the landscape. Pests/Problems. Eastern tent caterpillar was observed hatching in a sheltered location in Centerville. Lily leaf beetle adults have already been observed, even though lilies are barely breaking the ground. We anticipate hatch of winter moth caterpillars in the very near future and suspect that the hatch may be beginning in sheltered, warmer pockets of the Cape. Ants are active in thin turf. Winter annual weeds are green and growing.

Southeast Region (Hanson) - General Conditions: Nice spring weather continues except for the slight snow shower Tuesday evening, April 12! Cooler weather the past few days has kept plant development in check. However, forsythia buds are turning yellow and should open soon. Lawns continue to green up. Cornus mas, Pieris japonica, early tulips and daffodils, Vinca minor, Pulmonaria sp. Pussy Willow, crocus, Helleborus niger, H. foetidus, H. x hybridus (Helleborus Orientalis) are in full bloom. Star magnolia is starting to bloom in some areas and is in full bloom in warm, sheltered locations. Snowdrops, Taxus sp. and Hamamelis x intermedia 'Pallida' are past bloom. Pests/Problems . Adult deer ticks are active; conduct tick checks frequently, especially after yard cleanups. Extensive damage to plants by browsing deer continues to be reported by many people from many towns. Reports have come in that caterpillars of Winter Moth have hatched in some areas of Plymouth and West Bridgewater and also in Needham. In Hanson, winter moth caterpillars have not started to hatch. Egg development may be enhanced in some areas by microclimate. Eastern tent caterpillars have started to hatch in Hanson.

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

Central Region (Boylston) - General Conditions: Cooler weather has slowed the rush to bloom, still many early bulbs and perennials are showing color. Chionodoxa, scilla, Iris reticulata, early narcissus, Bergenia, Helleborus niger and H. hybridus are providing color. White Forsythia (Abeliophyllum distichum) is in full bloom, Pieris japonica ‘Brouwer’s Beauty’ and P. floribunda are beginning to bloom.

Pioneer Valley Region (Amherst) - General Conditions. Crocus and hyacinth are in full bloom, daffodils are beginning and many tree and shrub buds continue to expand and break open. The grass is really greening up and high soil moisture is abating. Korean rhododendron is flowering near buildings, while star magnolias in other areas on campus are approaching full bloom. Pests/Problems. There is scattered branch dieback and leaf browning on some rhododendrons, especially those in open situations. Most of the damage is probably due to winter wind and sun exposure as well as breakage from snow load and physical injury.

Berkshire Region (Great Barrington) - General Conditions: Plant development is proceeding slowly but steadily as the weather cooled to below average temperatures over the past week but a warm-up should accelerate plant growth. Soils are drying rapidly due to sun, wind and lack of precipitation this week. Pests/Problems. Mosquitoes, ticks and various wasp species are active but no major pest issues are yet apparent.

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

Lepidopteran caterpillars:

• Gypsy Moth - Monitor now for the tawny colored egg masses that can be found on tree trunks, rock walls and elsewhere. Use the numbers as an indicator of population size. This pest increased in numbers statewide last year and is expected to be problematic in some areas this year, especially Southeastern MA. Eggs will hatch at 90-100 GDD, which is typically the first week in May in much of MA. There are no control measures for the egg stage.
• Winter Moth - Most coastal towns as well as some inland towns in MA will experience large numbers of this introduced pest this spring. Much damage is expected. Inspect now for the loosely scattered eggs on the trunks and major branches of oaks, maples, fruit trees and blueberry plants. Eggs are a pinkish-orange but are starting to turn dark in color and are hatching in warmer /sunnier locations. The new tiny larvae will crawl into buds and feed. Some have been found already in Bridgewater in lilac buds. Horticultural oil sprays for the eggs may have a limited effect but this pest is currently in huge numbers and scattered throughout host plants in the landscape and forest. Additionally, it is now too late in the season for dormant oil sprays. Treatment for the caterpillars while they are in the buds is extremely challenging. Once they become free-feeders, after bud break, they can be managed with Bacillus thuringiensis ssp. kurstaki or a spinosad product (e.g. Conserve SC™) or a tebufenozide product (e.g. Confirm™).
• Forest Tent Caterpillar - Also on the rise as a serious defoliator, this caterpillar mostly prefers oaks in MA but can be a pest on maples, crabapples and other deciduous hosts. They will appear after the buds open and will be free-feeders. Treat the same way as winter moth.
• Eastern Tent Caterpillar - Common to Malus and Prunus species, this native defoliator was present in high numbers last year across much of the Northeast. Inspect now for the charcoal-like egg masses around the host stems. Remove and destroy when found. Although, in certain areas, egg hatch has already begun. Once they become free-feeders, treat with B.t.k. or a spinosad product or a tebufenozide product.
• Fall Cankerworm - This native pest is still in high numbers, especially in towns north of Boston. It, primarily, can be found on oaks but it has a rather wide deciduous host range. Eggs will hatch around 50 GDD (soon after bud break). Treat with a B.t.k. product or spinosad or tebufenozide.
• Fruitworms - This complex of caterpillars will become active between 50 and 100 GDD. They initially look like winter moth but most have 5 pairs of prolegs and not two. They are free-feeders and have been increasing in numbers over the past 2-3 years. Oaks, maples and many other deciduous hosts are attacked. Treat the same way as the other Lepidoptera.
• Larch Casebearer caterpillars are becoming active. Right now they appear like little cigar-shaped pieces of needles on the trunks and branches. They will soon migrate to the buds where they will sit and wait for buds to open. They will then feed on the new foliage. Once feeding begins, treat with Bacillus thuringiensis var. kurstaki (B.t.k.) or a spinosad product or a tebufenozide product.

Beetles:

• Viburnum Leaf Beetle - Inspect all viburnum plants (those that are established in the landscape and nursery, as well as those that are newly arriving) for the presence of this unwanted pest. The indicator of its presence at this time of the year will be bare twigs that have a 'sandpaper' texture, which is a sign of the over-wintering eggs. Report any new findings in MA to Robert Childs, rchilds@psis.umass.edu, 413-545-1053.
• Lily Leaf Beetle - The bright red adults will be emerging from their winter dormancy soon. They will forage for food and eventually a mate. This is a pest of all true lilies (not daylilies), fritillaria, Solomons-seal and others. It is a devastating pest to true lilies. Eggs won't appear until mid/late May, which are laid in irregular lines on leaf undersides. Neem-based products, when applied every 10-14 days, can be effective against the larvae when they begin to appear. Other than that, certain pyrethroid insecticides may be necessary.

Piercing-Sucking Pests:

• Spider Mites - Inspect the needles and stems of conifers now for the over-wintering eggs of such pests as spruce spider mite. It is too late for a dormant oil spray. One of the growth regulator products that affects developing mite eggs may be useful.
• Hemlock Woolley Adelgid (HWA) - This pest experienced a phenomenal reduction in population numbers during the winter of 2003/2004. However, by being milder, this past winter did not have the regulating effect on HWA as did the previous one. New eggs are now noticeable. Monitor for increasing numbers and treat with a horticultural oil spray (when plant phenology allows) and/or whenever the correct weather conditions prevail. Systemic imidacloprid products can also be of benefit.
• Mealybugs - Begin to inspect the inner branches for taxus mealybug. Treat when found.
• Balsam Twig Aphid . Stem mothers are active. Inspect host plants (mostly balsam and Fraser firs) and treat before they produce copious amounts of offspring. This pest causes new needles to be twisted and they will also be stuck together with large amounts of sticky honeydew.

Scale Insects:

• Armored Scales - A group of scale insects characterized by a hard, convex covering over their bodies, such as pine needle scale, euonymus scale, juniper scale and white prunicola scale can be monitored now. Treat with a horticultural oil spray when plant phenology and correct weather conditions prevail.
• Soft Scales - Tuliptree scale and azalea bark scale can be monitored now. Look for sooty mold on the host plants. In the case of tuliptree scale (found on tuliptree and magnolia), one can also find the large, dark brown coverings on the stems. Azalea bark scale will appear white and cottony and will mostly be found in branch axils along the main trunk. Treat with a horticultural oil spray or systemic imidacloprid. These can be difficult to manage and may require future monitoring and treatments.

Gall Formers:

• Eastern Spruce Gall Adelgid - Nymphs are active at the base of buds and will soon stimulate the new shoots to become galls. Treat before gall formation occurs.

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 that are known to be susceptible to these types of diseases.

Favorable Time To Prune - This is an effective time to prune branches from rosaceous plants infected with the fire blight bacterium. Remove dead stems from crabapple, apple, pear, firethorn (Pyracantha sp.), hawthorn, cotoneaster and related plants. Lilacs with dead shoots from bacterial blight also benefit from their removal. Disinfect pruning tools between each cut with 70% ethyl alcohol or a 10% bleach solution.

On plum and cherry trees that are infected with black knot canker look for swollen branches (~twice the normal diameter). Not only 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. Prune knots or swelling branches at least 3 - 4 inches below visible swelling. Remove the debris from the site and destroy it because the black knot fungus can produce spores on pruned branches. Removal of knots from Prunus species in nearby sites improves management of black knot on the “principal” trees. Apply registered fungicides to specimen trees from when the buds break open through the end of active shoot elongation to protect vulnerable green shoots from infection.

Sudden Oak Death (SOD), also known as Ramorum blight. Since 1995, oaks and tanoaks have been 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. SOD was first seen in 1995 in Mill Valley (Marin County) on tanoak. Since that time the disease has been confirmed on various native hosts in fourteen coastal California counties (Marin, Santa Cruz, Sonoma, Napa, San Mateo, Monterey, Santa Clara, Mendocino, Solano, Alameda, Contra Costa, Humboldt, Lake, and San Francisco) and in Curry County, Oregon. Molecular tests detected evidence of P. ramorum on a single tree in Nassau County, NY but the organism could not be isolated.

Research being conducted by the Agriculture Research Service, US Forest Service, Universities and others is under way to better identify hosts, methods of detection and effective treatments. Currently, 64 plants are regulated; two of these are at the genus level (Camellia and Rhododendron). There are no chemical treatments currently available to eliminate the disease in nursery stock.

Landscape, Nursery and Urban Forestry Diagnostic Lab Report

The following are some of the interesting samples received at the UMass Extension Landscape, Nursery, and Urban Forestry Diagnostic Lab in Amherst during the period of April 4 through April 8, 2005:

• White fir - mature tree with scattered branch tips that were killed last spring as they were developing; Sirococcus blight.
• Norway spruce - mature tree on site crowded and shaded by adjacent plants with thinning and premature needle loss; Rhizosphaera needle cast/insufficient sunlight + poor air circulation.

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