Mild weather creates differing scenarios for Maine insects

ELLSWORTH, Maine — Fewer mosquitoes, more grubs, but no discernible difference for black flies or bees.

According to entomologists in Maine, that’s what the mild weather this winter has done so far for insect populations in the state.

Insects that thrive in Maine’s vast rural and wooded areas tend to disappear in the winter as cold and snow set in and then re-emerge with the spring thaw, which often is called “mud season” in the most northerly state on the East Coast.

But with a winter like this past one, which had little snowfall and relatively mild temperatures, the conditions have resulted in a mixed bag of effects on insects.

“Having a warm winter and dry weather does make a difference for insect survival for a lot of [species],” David Struble, state entomologist for the Maine Forest Service, said Monday afternoon.

Mosquitoes are one insect that likely will be less prevalent this spring because of the lack of snowfall, according to James Dill, entomologist with the University of Maine Cooperative Extension. Dill said Monday that because there was little snow this winter, there won’t be many vernal pools created by snowmelt. Mosquitoes need still water to breed, he said, and the lack of snow means there are fewer pools where their eggs can hatch.

But the winter weather should not be taken as a predictor of whether mosquitoes will be prevalent this summer, he added. Several days of wet weather would give mosquitos the water and time they need to spawn in earnest.

Struble agreed that the lack of snow will affect the number of spring mosquitoes.

“That should be way down,” he said. “I don’t think we’re going to see the population of spring mosquitoes that we might otherwise see.”

According to Steve Elliott, owner of New Land Nursery & Landscaping in Ellsworth, the big insect issue this spring is likely to be grubs. Any insect that lays its eggs in shallow soil, as beetles do, he said, will benefit from the dry soil and warm weather.

“I’m expecting to see tremendous increases in those,” Elliott said. “You’re going to see a lot of problems with lawns.”

Dill echoed Elliott’s prediction, adding that the relatively mild fall in 2011 also is contributing to the issue. The beetles had more time in the fall to feed and lay eggs, he said, so there likely will be more grubs this spring. And what damage the grubs don’t do to the grass will be done by crows and other predators that dig into the soil looking for a meal, he said.

Dill said the prevalent type of beetles in Maine used to be the Japanese variety, but now more than 90 percent of them are believed to be European chafers. He said he recently dug through a section of lawn 6 feet long by 2 feet wide outside his house in Old Town and found roughly 100 such grubs burrowed into the grass.

“They are showing up way earlier than they normally would,” Dill said.

By some reports, black flies have emerged maybe a little earlier than normal, but not by much.

Elliott said his nursery is bordered on multiple sides by running water, where black flies breed, but the springtime pests have yet to make themselves known to him or his employees.

Struble said nonbiting male black flies are starting to emerge, but the biting females haven’t yet.

According to Dill, black flies usually appear around May 1 each year.

“It’s not real unusual for black flies so far,” Dill said.

Dill said that so far there’s no indication bees will suffer as a result of milder winter weather. He said that warmer temperatures can boost the spread of mites that affect bees, but he said milder temperatures also can help boost the strength of bees and their resistance to parasitic mites.

“That’s when mites are a bigger problem,” Dill said of colder winters that can force bees to expend more energy staying warm. He added that winters that are too warm, however, can lure bees out of their hives prematurely, which also can affect their numbers.

He said Cooperative Extension staffers have yet to receive any calls this spring about dead or dying bees.

But Tony Jadczak, state apiarist and bee inspector, is warning beekeepers that the conditions this winter and spring are reminiscent of 2010, when an explosion in mite populations killed off many bee colonies in Maine.

“The bees are coming out, but so are the parasitic mites,” Jadczak told the Kennebec Journal. “What I’ve seen in my inspections is elevated mite loads because of the good health of the honeybees. If it tracks like it did in 2010, we’ll have a huge die-off in the fall and winter.”

Maine doesn’t have enough bees in the state to pollinate all the crops, so thousands of bee hives are brought in by commercial beekeepers every year.

As for other insects, ticks might be out in greater numbers this year, according to Struble. The mild winter has been easier on animals such as deer that carry ticks, he said, and so has been easier on parasitic insects, too.

Struble said the mild weather could enable the hemlock woolly adelgid to increase in numbers and spread further into Maine in 2012. Elliott said other pests that hatch and feed on vegetation such as tent caterpillars also are expected to be prevalent.

Elliott said environmentally friendly oil treatments are available for killing insects that can kill trees. This time of year is a good one to take preventative measures, he added.

“You still have time as we speak to treat that,” Elliott said. “You’re going to see a lot of them this year.”

The Associated Press contributed to this report.

Follow BDN reporter Bill Trotter on Twitter at @billtrotter.