Ticked, Bugged, A Mite Angry? Must Be Those Insects

GREEN PIECE

August 25, 1991|By Mary Gold

Experienced Howard County gardeners gloomily shook their heads last spring: the mild winter meant lots of summer bugs. The soon-to-appearhordes of flea beetles, aphids and Japanese beetles were a foregone conclusion. The smart gardener prepared for the fray.

Like many weather-related adages, the warning seems to straddle the line between science and folklore. And like many such sayings, its validity, like beauty, may depend on the beholder.

Sometimes we see what we think we ought to see. Sure, there have been zillions of insects this summer, but have their numbers been greater than normal?

Yes and no, says Mary Kay Malinoski, insect specialist at the University of Maryland Cooperative Extension Service Home and Garden Information Center in Clarksville. Environmental factors such as unusually warm winters can affect insect populations drastically. But each insect species' vulnerability is different and depends on its life cycle.

"Insects that overwinter as adults and larvaeare more susceptible to winter weather than those that overwinter aseggs," Malinoski says.

Our dry, hot summer is also having a tremendous effect on numbers of insects. Some pests, like spider mites, are actually thriving in the heat; others are suffering. In addition, the weather is stressing our plants and trees, thus making them more vulnerable to insect and disease attack.

The staff at the Home and Garden Information Center is in a good position to know what is bothering area gardeners.

The horticulture specialists answer a flood of questions every day via an 800 number. According to phone calls, the incidences of flea beetles, cucumber beetles and locust leafminers -- those insects creating all the brown trees along our roadways -- are up; aphids and fleas are down.

The two pests that have been of major concern this summer, says Malinoski, are spider mites and Japanese beetles. The spider mite is not an insect, but a relative of spiders and ticks, tiny as a pinhead, and very destructive to numerous plants, including ornamentals like junipers and English ivy.

Even tomato plants have shown up with spider mite damage this summer. It loves hot, dry weather, reproducing rapidly. Because they are so small, spider mite damage may remain unnoticed until irreparable harm is done.

The undersides of leaves appear stippled with tiny indentationsat first, then the leaves turn yellow, dry and fall off. The mites are most easily detected by holding a piece of white paper beneath a branch with suspected mite damage and tapping the branch sharply. Resulting reddish, moving specks on the paper are proof of the spider mites' presence.

Often a forceful spray with a hose will knock them off. The moisture will discourage their return. According to kind of plant infected, insecticidal soap, horticulture oil and labeled miticides may also be useful if the problem is severe.

Japanese beetles,on the other hand, are far from a subtle presence. The brassy, iridescent green, half-inch beetles have overrun many areas of the countrythis summer. They buzz clumsily into the air when startled and eat, usually communally, like crazy.

Although entomologists report thatthese beetles will feed on any of 275 plant species, this greedy eater seems to single out the most valuable and attractive ornamentals, fruit trees and garden plants for its meals.

Because of the warm spring, adult Japanese beetles appeared two to three weeks early, and,although dwindling in numbers now, they are still active.

Malinoski reports that it isn't clear at this point if there are unusually high numbers of beetles this summer or if the overwhelming effect of the beetles is due to larvae emerging as adults all at once instead ofin increments over the summer.

The "synchronous" appearance, as she calls it, of the beetles, was due to the hot dry spring. The foliage and flowers of raspberry bushes, roses, peach trees and hollyhocksare great favorites. Often, just the skeletons of the leaves are left on the plants.

The eating of corn silks as they emerge from the unfertilized ear have diminished, along with the drought, the corn harvest.

"They are eating things that I've never seen them eat before," says Malinoski, "like okra and sassafras."

But the damage thatadult Japanese beetles do is only half the story, because these insects lead a double life. The first year of their lives is spent as grubs in the soil. Although almost as undiscriminating as they become asadults, the grubs prefer turfed areas where they munch on tender grass roots.

In large numbers, the grubs can causes the grass to turnbrown in patches and die. Peeling back affected turf will reveal thecurled up white grubs with tiny brown heads.

Many parts of HowardCounty are vulnerable to grub infestation, especially newly developed areas.

When builders remove top soil, and with it the natural microbial controls of beetle grubs, and then add sod, carefully watering it in, the conditions are ideal of the Japanese beetle.

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