PORTLAND – The heavy spring rains are being credited for a decline in the browntail moth population in coastal southern Maine.

The moth numbers are down because the rains in May and June fostered the growth of disease and parasites that in turn have decimated the moth population, said Maine Forest Service entomologist Charlene Donahue.

“The population is way down from what it has been,” she said.

Browntail moths, which can cause respiratory problems and rashes similar to poison ivy, have been a problem in recent years in the Casco Bay region.

Even though the numbers have fallen the past couple of years because of unfavorable weather conditions, the moths were a big enough problem that rangers last year were warning visitors about them at Wolfe’s Neck State Park in Freeport.

“It was bad enough that people didn’t come,” said Theresa Oleksiw, a ranger at the park.

But the moth counts are down this year, and rangers aren’t issuing any warnings, she said.

This year’s decline in the browntail population isn’t a total surprise. Surveys in January and February confirmed that the population appeared to be falling.

The decline comes as the state is looking into whether spraying pesticides to control the pests is harmful to marine life such as lobsters.

The Maine Board of Pesticides Control has scheduled an information-gathering hearing for July 21 in Freeport to discuss the risks and benefits of spraying.

Even though the moth population is down for now, it probably will bounce back in the future.

“My guess is that it’s going to stay down for a while,” Donahue said. “But is it gone? No, it will come back at some point.”

The browntail moth was brought to the United States accidentally from Europe more than a century ago. The insect spread and at its height it covered nearly 60,000 square miles in the Northeast and eastern Canada, where it was known to defoliate late tracts of hardwood forests.

Populations have slowly declined, and the insect today is rarely found outside of Casco Bay and Cape Cod in Massachusetts, according to the USDA Forest Service.