A control may have been found for the dreaded gypsy moth. The Department of Agriculture's Science and Education Administration is optimistic.

The moth, a destroyer mainly of hardwood trees, was formerly confined to the northeastern United States but now threatens the oak-hickory forests of the East and Midwest. Populations are now large enough to defoliate millions of acres of forest and urban areas, and it is established in parts of Maryland and Virginia.

Gypchek, and isecticide developed at the U.S. Forest Service Insect & Disease Laboratory, is under test in six states.

Made from the gypsy moth nucleopolyhedrosis virus, Gypchek is a biological control that has proved effective in small-scale tests. The virus poses no known danger to birds and animals that feed on moth larvae and has been registered by the Environmental Protection Agency.

Until now there has been no way to stop the European moth's spread from New England, where it escaped from an experimental silk-producing project. While its caterpillars will eat leaves of many other trees, oak is preferred. Deciduous trees may be completely stripped and grow new leaves by the end of summer, but several defoliations in a row usually are fatal.

Evergreens may be killed by a single defoliation. Deciduous trees weakened by defoliation are more susceptible to attack by borers and other pests.

Bearded irises in the garden multiply rapidly and usually need to be dug and divided every four or five years. Do it soon after they finish blooming, when they go dormant for a few weeks.

Siberian and Japanese irises do not need to be divided as often; Siberians may remain in good condition for 10 years or longer. But sooner or later the size and quality of the flowers may deteriorate and they can be improved by division.

Although bloom should be fairly good on bearded iris the first year after division, the best bloom occurs in the second, third and fourth years, according to the American Iris Society. Don't divide your clumps too soon, however. Wait until they become crowded and the number of blooms starts to decline. Improve the soil where they are to be replanted with compost or organic matter.

To divide, bring up the clump with a spading fork and wash off the soil. Cut the leaves back to about one-third of their previous heights. This will help them to become established after replanting. Cut away the oldest of the thick underground stems. These can be replanted.

Cut the youngest underground stems into sections of five to six inches, each with two fans of leaves, and replant.

Q - I've tried three times to start cannas from seed without success. What's the secret?

A - Paience. Canna seeds need 50 days to a year to germinate.

Q - I have a beautiful clematis, and want more just like it. Can I root cuttings?

A - Clematis can be propagated by layering, air-layering, cuttings in midsummer, seed and grafting.

Q - When should I palnt seeds of geraniums to have plants large enough to bloom in the spring?

A - Sow the seed in August. Transplant to pots when the sedlings are large enough to handle and continue to give them larger pots until they are in 4-or 6-inch pots. Seed for fall flowering can be sown in March.