Cape trees were largely spared the scourges of that voracious triumvirate - the winter moth, forest tent, and gypsy moth caterpillars - this summer.

"There were some localized pockets, but there wasn't any widespread defoliation," said Roberta Clark of the Cape Cod Cooperative Extension. But that doesn't signal an end to the plague. Next year, given favorable weather conditions, the pests could be back in greater numbers.

That could affect orchards, blueberry growers and the average homeowner. After three or four years of complete defoliation by winter moths or gypsy and tent caterpillars, even larger trees can die, Clark said. Stands of dead trees in Sandwich and along Route 3 in Kingston testify to that, she added.

In the case of the gypsy moth and forest tent caterpillars, the humid, cool conditions this past spring helped two strains of the entomophagia fungus attack and decimate their populations. One of those strains is itself an alien species that was introduced in 1989 to attack the gypsy moth. Biological "controls" like the fungus sometimes take a decade or more to establish themselves.

University of Massachusetts entomology professor Joseph Elkinton believes the 1989 fungus is just now taking a major toll on gypsy moths.

For winter moths, it was the hard freeze following Thanksgiving that trapped many of the adult moths in the frozen ground before they could emerge and take their mating flight.

The winter moth has no natural predator, other than cold weather. Elkinton believes the only thing that will stop the winter moth is to introduce another biological control, a tiny fly - Cyzenis albicans - that lays its eggs inside moth cocoons. The fly larvae consume the moth pupa in the cocoon before it can emerge.

"The idea of a biological control agent is that, once it has established itself, it will suppress the population and keep it low forever," Elkinton said. UMass researchers released 1,000 of the flies in Hyannis this spring, hoping to infect as many winter moth cocoons as possible and, along with a similar release in Falmouth last year, get the Cape's parasitic fly population up and running.

The UMass program was funded this year by $150,000 set aside in the university budget by the state Legislature that pays for a full-time technician and several students who help raise and distribute the flies.

Elkinton said outbreaks of winter moths in the Pacific Northwest in the 1970s, and in Nova Scotia in the 1950s and '60s were controlled by introducing the parasitic flies. The winter moths are an alien species accidentally introduced here from Europe, where the flies are a natural predator.

Clark said that biological controls like these flies must undergo a rigorous certification process to ensure they will attack one specific species. Elkinton is hoping that the state continues to fund his project.