Voracious gypsy moth caterpillars in Northern Virginia have ravaged 14 times the territory affected last year, devouring trees in 5,200 acres this spring compared with 375 acres in 1984.

"It was worse than we had expected," said Donald Kludy of the Virginia Department of Agriculture. "This summer provided perfect conditions for the gypsy moth."

Local experts, who had predicted that 2,500 acres would be affected this season, expect the caterpillers to attack with even greater force next year because the insects have left behind millions of egg masses that will hatch in the spring.

The gypsy moth has left its mark around the state: stands of leafless, winterlike trees, their leaves devoured by the moth's caterpillars.

What the experts fear is that the moths will destroy even the sturdiest of trees after an infestation cycle of two to four years by eating the tree's life-sustaining leaves. Repeated resprouting of leaves drains a tree's energy and eventually can kill it.

Loudoun County was the worst hit in Virginia, with 3,500 acres stripped in the heavily forested Blue Ridge and Catoctin mountain ranges along the Clarke County line. Fauquier County had 1,500 acres damaged along the Warren County line, also primarily on ridgetops.

Even suburban Arlington County felt the pressure of the southern migration of the moth. Caterpillars devoured 20 acres in the exclusive Country Club Hills area.

Other suburban Virginia counties had higher moth populations, but did not experience defoliation, Kludy said.

As the insects continue their migration south, nearby Maryland counties had the most defoliation of the Washington area. The statewide figures totaled 83,000 acres in Maryland this season, compared with 42,000 last year.

Frederick County alone lost leaves on trees in 8,198 acres this spring and Montgomery County, which had defoliation for the first time, lost 181 acres of trees, including areas in suburban Bethesda and Chevy Chase.

The surrounding Maryland suburban counties of Howard, Anne Arundel, Prince George's, Calvert and Charles had higher counts of moths, but did not experience defoliation.

While the District of Columbia also has had rising populations in its many wooded parks and neighborhoods, local experts say there is no immediate worry about defoliation.

A main hope for curbing the impact of the insect is for homeowners to get involved in identifying locations of egg masses.

The flat, fuzzy, beige egg masses can be found "almost anywhere" outdoors, according to Nathan Erwin of the Maryland Department of Agriculture, such as the underside of limbs, on lawn furniture or even in stacks of tires or trash.

Agents at local agricultural extension offices can answer questions about how to do away with the egg masses, or residents can sign up to have their trees sprayed in the spring.

The egg masses, which can hatch from 250 to 1,000 moths each, were laid in July and are due to hatch next April.

Beginning this month, experts will be locating and counting the egg masses in an effort to assess the coming flight season and plan spraying and other efforts to combat the annual onslaught.

Among the programs to fight the pest are: applying nontoxic pesticides, releasing gnat-sized wasps that destroy the moth's larvae but do not sting humans, and hanging "lure tapes" on trees. The tapes release an odor that is intended to confuse male moths and prevent them from finding females for mating.

Kludy concluded that the battle against the insects will grow more difficult and costly.

"We anticipate it the infestation will continue to spread and we'll have to expand our programs," he said.

The moths' caterpillars that emerge next spring will be distinguishable by their rows of blue and red dots.

The moths will emerge as adults in late June or early July 1986 and begin mating, which is their sole function as fully developed insects before they die.