An all-out effort will be made in Maryland this year to save as many trees as possible from destruction by gypsy moths. It is expected there will be more of them in the state than ever before and they could defoliate many acres of trees of both forest and urban areas.
They are in Virginia also and last year some of them were trapped in the suburbs of Washington.
This insect was confined to the northeastern United States until recent years but now threatens the oak-hickory forests of the eastern half of the country and parts of the midwest. In 1978 the northern parts of Baltimore, Harford and Cecil counties were generally infested with spotty infestations in Frederick and Carroll counties.
There are four stages of the insect: egg, larva or caterpillar, pupa (cocoon), and adult moth, the males of which have wings and the females do not. Each stage occurs only once a year.
The caterpillars hatch when the weather warms in April or May. The young are small, less than an inch. Many will drop down from branches, each on a single silk thread and hang until the wind picks them up and blows them to other trees. This is the principal method of their natural spread.
Full growth caterpillars are 1 1/2 to 2 1/2 inches long, dark brown, hairy, and can always be identified by six pairs of red dots that occur on their back from the middle to the tail end.
A large caterpillar can eat a square foot of a leaf surface in 24 hours. Species favored are oaks, willows, poplars, alder, basswood, apple, gray and white birch, boxelder, hawthorn, larch, linden, mountain ash, roses, blue spruce and sumac.
Less favored but also eaten are cherries, elm, hickories, chestnut, hornbeam, maples, sweet birch, paper birch, yellow birch, sassafras, black tupelo, and larch. Older caterpillars will eat native eastern pines and spruces, red and southern white cedar, hemlock, beech and plum.
They will not feed on tulip or yellow poplar, sycamore, arborvitae, ash, catalpa, dogwood, hackberry, holly, horse chestnut, juniper locusts, mountain laurel, mulberry, osage orange, persimmon and walnut.
Normally deciduous trees can be completely defoliated in one season and not killed. They can even grow new leaves by the end of summer. Defoliation for several years in a row, however, is often fatal. Oaks that are defoliated for two years in a row may result in death of half of the affected trees. One defoliation can kill evergreens like pines, hemlocks, larch and spruce. Trees weakened by defoliation are more susceptible to attack by borers and other pests.
Gypsy moth caterpillars will not be found after early July. They enter the pupal stage in June and very early July. This stage is where the insect changes from caterpillar into adult moth which emerges during July. Eggs are deposited in late July and August in masses of 100 to 700 or more and covered with buff to yellowish hairs from the abdomen of the female. The eggs may be found on the undersides of branches, tree trunks, under loose bark, on stone walls, fences or any shady protected place.
While there are presently no control methods to stop the gypsy moth, the Maryland Department of Agriculture is releasing a number of insect parasites in the path of advance. Other parasites which attack only the gypsy moth are released as the infestation increases. The Department also maintains trapping programs and surveys which tell how fast and how far the moth is advancing.
In 1979 there will be a survey of all of the state with male traps on relatively close grids. A new, larger trap baited with a more potent lure, and a computerized form will be used to record the trap data, and efforts will be coordinated with those of surrounding states. There will be an increase in spray activities of about 20 "hot spots" mostly in Harford and Cecil Counties. Federal agencies may do more spraying mostly in Frederick and Washington Counties but no plans have been announced yet.
Large scale field tests will be made using lures. If it works, it may be the first time a pest has been controlled by confusion and frustration rather then physical harm.
Non-chemical measures can be taken to protect shade and ornamental trees around the home. For instance, destroying the egg masses will help reduce the pest population.
Another aid for home trees is to band the tree in mid-June with a sticky substance called Tanglefoot. Do not use any other materials, such as motor oils, because these substances may kill the tree. An alternative is to tie folded-over burlap or cloth strips around the tree. As the caterpillars migrate up and down the trunk, the strips trap them so they can be killed. The burlap should be checked every day.
Pesticides can be used by spraying equipment available to the average person will not spray higher than 25 feet which only protects small trees and shrubs. Sevin (Carbaryl) is effective but the drawback is it also will kill parasites and honey bees. CAPTION: Picture, Gypsy moth on a leaf.