Now we read there is a fungus that is decimating gypsy-moth caterpillars. It is related to one native to Japan that was introduced here in 1910, but then ''the scientists lost track of it,'' according to officials in the Department of Agriculture, until it ''re-introduced'' itself this spring. But why the long lapse of scientific attention and research follow-through on a potential natural control?

Similarly, there is a milky fungus that controls Japanese beetles, once used successfully, then dropped in favor of destructive, expensive and unsuccessful chemicals, and now effectively being used again. But again, why this long, costly detour around natural controls?

Like the others, our latest nemesis, Lyme disease, is also found internationally, this time by way of species of the Ixodes tick. But overseas it is not increasing out of control, apparently due to natural enemies. Will we vigorously research these possible natural controls and promptly introduce them in this country, if found? Or will the chemical industry again succeed in apparently violating the integrity of those who should know better?

In this case, the hunting lobby threatens to add to the destruction, aided by the Department of Environmental Conservation, which is heavily dependent on hunting fees for revenue.

How else explain their simplistic answer: Lyme ticks are found on deer, therefore kill the deer. That the tick would then resort more heavily to the other animals on which it is found, including humans, seems to be an oversight of the over-eager, or shortsighted, greed protected by willful ignorance.

In the meantime, a natural predator has also introduced itself in our area, capable of reducing not only deer but the numerous mice that are an important link in the Lyme-disease cycle.

The eastern coyote, considerably larger than its western relative, is seemingly made to order to fill the ecological vacuum created by the extinction of other large predators in our area.

However, typically, the D.E.C. response is to impose a long four-month kill season on coyotes before they even establish themselves and prove their worth.

Inefficient but lethal hunters and chemicals or more effective and harmonious natural controls: our choice - before it is too late. MARTIN BRECH Mahopac Mr. Brech has served as a preserve manager for the Nature Conservancy of Westchester in Mount Kisco.