At Last! Gypsy Moths Retreat From Their Hungry Attack


County To Spray Less Since Insects Are Abating

April 21, 1991|By Mary Gold | Mary Gold,Contributing writer

Gypsy moth caterpillars are an emotional subject here in Howard County.

The furry, crawly things climb everywhere, large trees are stripped of leaves in a week and caterpillar droppings (called "frass") shower lawns, patios and cars.

More than one Howard County homeowner has considered cutting downoak trees rather than face another season of the gypsy moth caterpillars.

Well, it's that time of year again. But state and local monitoring for gypsy moth egg masses in the county has shown that this spring we can expect a decrease in the gypsy moth population. The causefor this phenomenon is related primarily to natural enemies of the pest -- viral and fungal infections -- as well as past aerial sprayingof insecticides.

This spring's spray effort, conducted by the Maryland Department of Agriculture, will be very limited compared to previous years because of lower egg mass counts coupled with cuts in county financing.

In fact, several blocks scheduled to be sprayed were dropped just last month, says Scott Aker, county urban agriculture agent. And for the first time, he adds, the majority of areas to be sprayed are in the eastern part of the county, with 11 blocks out of 18 located east of Route 29.

The state's aerial spray program aimedat slowing down the advancing hordes of gypsy moth caterpillars is also a sensitive topic for some people.

In the first years of the program, there were vehement critics of the spraying. But as more people experienced first-hand the gypsy moth's voracious appetite and understood the insecticides involved, the complaints changed.

Most calls now are "why don't you spray my property?" say MDA officials.

Despite our slight reprieve from the gypsy moth caterpillar, there will still be areas with severe infestations. An improved county prognosis is not going to make the many besieged people in these places feel any better.

Some control, not elimination,of caterpillar relatedproblems is possible for many homeowners.

* Tactic No. 1: Maintain healthy trees.

It's important to understand that trees vary in their ability to survive defoliation.

Evergreen trees will usually die after one defoliation. Most deciduous trees, however, will enduresome damage and can even withstand complete loss of leaves, producing new leaves later in the summer.

The tree strains to do this, however, so helping it avoid other stressful conditions is important.

Adequate water in dry weather, proper acidity levels, uncrowded conditions, avoidance of soil compaction or construction around the rootswill add to a tree's longevity.

Even with optimum growing conditions, two or three years of repeated defoliation will kill most trees.

* Tactic No. 2: Destroy egg masses before they hatch.

Unlike some of our common insect pests, there is only one generation of gypsymoths each year.

The larva, or caterpillars, hatch from egg masses that are deceivingly un-egg-like -- irregular, buff-colored patches, 1 to 2 inches in diameter.

The egg masses are found on tree trunks, under rocks, inside lawn furniture, on sides of houses, almost any place imaginable.

This pest's prime method of spreading in the United States is through hitchhiking -- traveling as eggs on the unsuspecting homeowner's patio furniture, campers, bicycles, etc., to a new location.

All through fall, winter and early spring, egg masses can be scraped off and destroyed.

* Tactic No. 3: Don't confuse the gypsy moth caterpillar with the tent caterpillar.

Gypsy moth caterpillars look darker, hairier and have blue and red spots on their backs, as opposed to the tent caterpillar's white stripe.

Gypsy moth caterpillars don't make webs, prefer different trees and cause moredamage than tent caterpillars.

* Tactic No. 4: Band your trees.

Steve Parker, tree care supervisor for the county bureau of highways, likes to display a pair of before-and-after pictures.

One showstwo almost identical trees on neighboring lots before the emergence of gypsy moth caterpillars.

The second shows the same trees a few weeks later.

One tree is missing all its leaves; the other appearsnormal. The answer to their differing appearances is tree-banding during May and June.

Newly hatched caterpillars are not the giant eating machines of June. They are tiny, only one-sixteenth of an inch long, black and barely discernible as they climb up the dark trunks oftrees.

Most homeowners don't notice them until a few weeks later when they can see holes in the foliage overhead. In other words, don't wait to see them to act.

Girdling the trunks of susceptible trees with a barrier now, just before hatching, will help keep smaller caterpillars from reaching the leafy tree tops.

Sticky tape, or sticky trap substances like "tanglefoot," spread on a 2-inch-wide band oftape around the tree will halt them. Direct application of tanglefoot onto the tree is not recommended as it may damage the bark.

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