Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, May 26, 1994 TAG: 9405260073
SECTION: CURRENT PAGE: NRV-6 EDITION: NEW RIVER VALLEY
SOURCE: Joe Hunnings
DATELINE: LENGTH: Medium
The HEMLOCK WOOLLY ADELGID has been in the United States since 1924. This introduced insect - believed to be a native of Asia - is a serious pest of eastern hemlock and Carolina hemlock. Spruce is a possible secondary host.
In the eastern United States it is established along the mountainous regions of the Shenandoah Valley, spreading southward along the Blue Ridge Mountains, and north to the mid-Hudson River Valley and southern New England.
White cottony sacs at the base of the needles are good evidence of a hemlock woolly adelgid infestation. These sacs resemble the tips of cotton swabs. They are present throughout the year, but are most prominent in early spring.
The hemlock woolly adelgid feeds during all seasons with the greatest damage occurring in the spring. It is dispersed by wind, birds and mammals.
By sucking sap from the young twigs, the insect retards or prevents tree growth causing needles to discolor from deep green to grayish green, and to drop prematurely. The loss of new shoots and needles seriously impairs tree health. Defoliation and tree death can occur within several years.
Application of a 1percent solution of dormant oil now is recommended for control of hemlock woolly adelgid. One application with complete coverage of the tree should provide 100% control. Following treatment, monitor the situation.
CAUTION: Excessive fertilization can worsen the problem with adelgids.
PINE BARK ADELGID. A close relative of the hemlock woolly adelgid, this insect is very conspicuous now because it produces large amounts of flocculent wax filaments that give pine tree trunks a characteristic white-washed appearance. The adelgids feed on tree trunks by sucking sap from the phloem tissue. Permanent damage should not result if the trees are otherwise healthy and not under any additional stress. Dormant oil, insecticidal soap and carbaryl are recommended insecticides in cases where the tree appears to be damaged and declining.
SEED CORN MAGGOT Delia platura (Meigen). If you have recently noticed many small flies on flowering dogwood, you may have a problem with seed corn maggots in your garden this spring. Adult seed corn maggots are active when dogwood is in bloom. They lay their eggs in cool, moist soil near newly planted seeds, onions, and potatoes.
After hatching, the larvae destroy the young plants. The entire row may fail to emerge. If you suspect seed corn maggots, check for small white maggots associated with rot and decay. The best strategy is to replant; only the first generation of this fly causes damage.
By the time the second planting is in the ground, the weather will be too warm and dry for them; seed corn maggots are mainly a problem in cool, wet springs. In gardens with chronic problems, use a granular soil insecticide, such as diazinon, at planting time.
SLUGS. These delightful creatures leave slime trails and chew ragged holes in bedding and garden plants. They can be controlled in several ways:
Beer baits - the old standard: Place a shallow dish in the ground so that the lip is at ground level and fill with cheap beer.
Oyster shells: Use crushed oyster shells (a chicken feed supplement) around the base of prized plants.
Diatomaceous earth or wood ash: Place around plants in the same manner as the oyster shells.
If all else fails, use slug baits that contain mesurol.
BORERS. Trees damaged by the winter ice storms will be susceptible to attack by borers. Check for loose bark and tunneling near wounds. Prune infested sections of the tree and promote vigorous growth by watering and fertilizing. Other insect pests to be on the lookout for now include: aphids on the undersides of leaves of many species; bagworms - small sacs found mostly on conifers; boxwood leafminers, mites and psyllids - call the Extension Office for details; eastern tent caterpillars and spruce mites.
For help with your garden questions, visit with our Extension Master Gardeners at Lowe's in Christiansburg. They will staff a plant clinic from 8:00 a.m. till 4:00 p.m.Saturday. You can bring them samples of insects and diseased plants for diagnosis or just chat.
by CNB