BRUNSWICK

The Maine Forest Service warns there will be a higher than usual population of browntail moth caterpillars which can have ugly side effects for humans — and it’s too late to do anything but avoid them at this point.

The Maine Forest Service forecasts, “At this time it is not possible to accurately predict the future populations of this pest in Maine. The insect is likely to remain a coastal problem. Although not limited to this area, persons within five miles of Casco Bay, and those on the islands in the bay should be especially aware of the problem and avoid handling the caterpillars if they are encountered.”

Forest entomologist Charlene Donahue said recently that “it’s really too late to do anything about getting rid of them.”

Right now the caterpillars are really big and they have molted several times, so even if you treat for them right now, she said, “it’s not going to reduce the amount of itch this year.”

The infestation will be worse than last year, Donahue said. The department conducts a roadside winter survey for browntail moth, determining if there are a handful, hundreds or thousands of webbed nests and based on that, estimate populations. This last winter, those nests numbered in the thousands, she said.

In the fall, colonies of larvae build nests in trees containing 25 to 400 or more larvae.

The caterpillars molt as they grow and each time they molt, they have microscopic hairs that float around in the air. They molt six times and have one more molt to go, Donahue said.

The caterpillar feeds on hardwood tree and shrub foliage — such as oak, shadbush, apple, cherry, beach, plum and rugsa rose — which can reduce the growth of trees or even kill them.

The hairs can cause rashes on human skin, similar to poison ivy and can be very severe for some individuals. According to the Maine Forest Service, the rash results from a chemical reaction to a toxin in the hairs (setae) and physical irritation as the barbed setae become embedded in the skin. Inhaling the hairs can also cause respiratory distress.

People should take precautions, Donahue said. For example, if they are in a browntail moth area, mow when the lawn is wet, wear pants and long-sleeve shirts and don’t hang your clothes out. If you do get a rash or have respiratory distress and go to the doctor, tell them it could be browntail moth.

Donahue cautioned that even people who have never experienced symptoms from the toxic caterpillar hairs are not safe, “because it’s something like poison ivy and you develop a sensitivity over time and the more you get exposed, the more likely you are to become sensitive over time.”

The time people can take action to reduce the number of browntail moth caterpillars on their property is in the winter when the leaves have fallen from the trees. Donahue said look at the top of the oak and apple trees in particular. If you see what looks like leaves still on the tree at the end of the branches webbed together, that’s where the browntail spend the winter. If you can reach those nests, cut them out and drop them in soapy water or burn them. If they’re out of reach, contact a licensed pesticide applicator about removing them as they have the proper equipment.

There is a specific state law regarding treating browntail moth near the ocean which impact many property owners in the Midcoast. Donahue said Harpswell has a restriction on what chemicals can be used in town.

The option to spray pesticide by air is a complicated issue for lots of reasons. There is a concern about the impact on lobsters which the chemicals that kill browntail moth can also potentially kill lobster if it gets in the water.

“I’m always on the lookout for something we might be able to do,” Donahue said. There have been four smallgrade treatments of a virus specific to browntail moth in the past, “but we haven’t seen any positive results from that yet so we are still looking for novel ways to handle browntail moth.

“We want a disease or parasite very specific that will take care of one problem with control and not cause problems other places,” when it comes to biological controls.

Another avenue of treatment is a bacteria insecticide called Bt that has different formulations for different insects, Donahue said, and she learned this past winter there was a reformulation for tree pests that may be effective for browntail moth.

However, “browntail moth is a very small problem,” Donahue said. It’s a problem that only occurs in North America along the coast of Maine and Cape Cod, making it difficult to get funding for research.

The browntail moth is an invasive species introduced to Somerville, Mass., from Europe in 1897 and had spread to New England states, New Brunswick and Nova Scotia by 1913. According to the Maine Forest Service website, populations have decreased due to natural controls until the 1960s.

Donahue said for a long time the browntail moth was very contained to the coast of Maine and primarily Casco Bay. It has spread down to Kittery and into Hancock County, occasionally, but remained right on the coast. The past few years there have been some small infestations inland, such as in Turner, Waterville and Augusta.

“We don’t know why it particularly likes the coast,” Donahue said.

PRECAUTIONS TO AVOID adverse affects of poisonous Browntail moth caterpillar hair (setae):

— Avoid places heavily infested by caterpillars. Campers should plan their stays on uninfested islands.

— Take a cool shower and change clothes after any activity that might involve contact with browntail moth hairs.

— Dry laundry inside during June and July to avoid having the hairs become impregnated in clothing.

— Wear respirator, goggles and coveralls tightly closed at neck, wrists and ankles when performing activities that stir up caterpillar hairs (mowing, raking, weed whacking, removing pupal webbing from eaves and boats).

— Perform those tasks that stir up caterpillar hairs on damp days or wet down material with a hose to keep hair from becoming airborne.

— Use caution cleaning debris left by caterpillars because the toxin on the hairs remains a hazard for a number of years. Summer residents should keep this in mind when opening cottages that have been closed all winter.

— Consult your physician if you develop a severe reaction to the browntail moth.

— The chances for contacting browntail hairs increase during dry windy conditions.

For more information visit www.maine.gov/dacf/mfs/forest_health/insects/browntail_moth.htm.