BATH

Bath City Arborist Kyle Rosenberg has spent his spring cutting browntail moth nests out of oak, apple and cherry trees around the city. Though he said cutting down the nests should help reduce the invasive insects’ numbers this summer, Rosenberg admitted there are just too many nests to keep up with.

“By seeing the nests we see now, browntail populations are going to be a lot heavier than last year, and probably much more widespread throughout the city,” he said.

Many Midcoast residents complained last summer when browntail moth nests began appearing in trees in their yards and around downtown areas. Matters got worse when caterpillar hairs and cocoon shells rained down onto lawns and became airborne during yard work, causing a variety of rashes and allergic skin reactions. The caterpillars emerge from their cocoons in July, the final stage of their metamorphosis into adult moths.

Rosenberg said that he and other arborists around the Midcoast began to take action last August as a result of the outbreak, injecting trees with pesticides — which Rosenberg said are harmless to the trees — to deter the caterpillars from eating the leaves and building nests in the trees.

The nests are built in August when adult moths lay new caterpillar larvae, and last through the winter. The larvae remains dormant in the nests until spring. Rosenberg said that the chemicals won’t work until the new leaves bud out this spring, and their effects on the browntail population may not be known until 2018.

For now, Rosenberg and other arborists have been cutting as many nests out of the bare trees as they can before the leaves grow in and make the nests hard to find.

“We’re getting near the end of the pruning cycle,” said Rosenberg. “The best time to prune is in the mornings. It’s cool enough so the caterpillars are going back into their nests at night, or at least congregating on the outside layers. We’ll have successful pruning for another week or so before the leaves start growing in, and the caterpillars start venturing out of the nests for good.”

Rosenberg said that even in midsummer the caterpillars will only travel 18 inches or so from their nests to feed, but the nests occur so frequently that trees will have the potential of being stripped mostly bare.

“Looking at the defoliation last August and September when the little caterpillars were making their nests for the winter, we were seeing trees that were defoliated 50-70 percent, which is alarming,” said Rosenberg. “In early September we went up to the transfer station in Bath where you get some elevation and have a good view of the treeline. The treeline had an orange tint to it, like in spring when there’s barely any leaves.”

Bath has seen a handful of browntail outbreaks in the past, Rosenberg said, but nothing of this magnitude. Sagadahoc County is the epicenter of the current outbreak, he said, which reaches as far north as Millinocket and as far south as Portland.

“Usually the nests have stuck to the north side of Bath where there is a lot of contiguous forest, but last year we were seeing nests down by BIW, further south, and as soon as you crossed the causeway into Phippsburg they were everywhere.”

Rosenberg said that he believes tree injections are the best path forward, but the window remains slim as to when the injections can be administered — August and early September only, when new nests are being built — and the number of personnel trained to administer injections is low. Only those trained in pesticide application and with the proper insurance can inject the chemicals, and Rosenberg said that the cost of the chemicals makes it an expensive proposition for both contractors and homeowners.

Bath recently received grant money to apply injections to trees in public areas such as parks and roadsides, as well as to large, landmark trees. But the waiting list for homeowners who want their trees injected or pruned is a long one, Rosenberg said.

“Folks who may have been unaware of browntails if they were gone for the winter or didn’t know it was an issue are trying to get onto a program, and are at best being put on a waiting list,” said Rosenberg. “All the service providers can only go to so many places.”

Until more arborists and other contractors become certified pesticide applicators, Rosenberg said the waiting lists will remain long. However, Rosenberg said homeowners are encouraged to prune their own trees as long as they are under 20 feet high.

“Browntails love fruit trees and smaller trees like that,” said Rosenberg. “If you have a ladder and a pole pruner and want to tackle those smaller trees, go ahead. But call an arborist if the tree is over 20 feet high.”

For more information on browntail moths, visit cityofbath.com or maine.gov.

bgoodridge@timesrecord.com