Fungus takes toll on Maine’s browntail moth populations

Tom Schmeelk, an entomologist with the Maine Woodland Carrier, issues out the place feeding injury from browntail caterpillars is plain at the leaves of a northern pink oak sapling. A fungus knocked again populations of browntail moths this spring, even though scientists don’t seem to be certain by means of how a lot. Ben McCanna/Personnel Photographer
A fungus that kills browntail moth caterpillars seems to have knocked again populations of the perennial pest in parts of Maine this spring, offering a reprieve from the yearly struggling brought about by means of the tiny hairs they unlock into the air.
But it surely’s too early to understand whether or not the fungus will lend a hand spur a statewide inhabitants cave in of the woodland pest or if that is the beginning of a protracted wreck within the yearslong infestation that has unfold alongside the coast and inland.
Microscopic hairs from the caterpillars may cause an especially itchy, lingering rash in other folks, generally from Would possibly to mid- to overdue June, sooner than the grownup caterpillars pupate and become into moths. Along with a rash, signs can come with breathing issues, together with problem respiring and inflammation of the lungs and throat.

There is not any knowledge that might display what number of people revel in those signs, however doable publicity to the microscopic hairs is connected to how tough the inhabitants of browntail moth caterpillars is each and every 12 months.
Thomas Schmeelk, an entomologist with the Maine Woodland Carrier, mentioned the elements this spring created “Goldilocks” prerequisites for the fungus to proliferate and kill the caterpillars – no longer too dry and no longer too wet. An epidemic that kills the caterpillars – additionally tied to climate prerequisites – has additionally contributed to lowering browntail moth populations.
“We’ve got many reviews of the fungus and the virus during the infested spaces of the state, and it’s a beautiful broad swath. It’s an excellent signal. We’re hopeful that is the start of the tip for this outbreak (of browntail moths),” Schmeelk mentioned.
Whilst rain is helping develop the fungus, an excessive amount of rain, just like the constant wet prerequisites in spring 2023, suppresses the proliferation of the fungus, which made it much less efficient in controlling browntail moth populations final spring, he mentioned.
However this 12 months, periodic heavy rainstorms have continuously been adopted by means of a number of days of dry climate, which has helped to disperse the fungus, Schmeelk mentioned. Spores from the fungus – entomophaga aulicae – desire a wreck within the rainy climate in order that wind can elevate them to different places to contaminate extra caterpillars.
Tom Schmeelk, an entomologist with the Maine Woodland Carrier, scans a gaggle of northern pink oak saplings for pupal packets the place feeding injury from browntail caterpillars is plain. Ben McCanna/Personnel Photographer
Schmeelk mentioned an aerial surveillance of leaf cover this August and September will lend a hand to quantify the variability and density of a brand new crop of browntail moth caterpillars that can be rising from eggs this summer time and later overwinter of their wintry weather webs.
The volume that the newly emerged caterpillars devour this summer time will have to lend a hand decide how efficient the fungus used to be in killing the grownup caterpillars this spring. Browntail moth caterpillars have a tendency to feed on leaves of fruit, oak, birch, elm and poplar timber.
The smaller inhabitants of grownup caterpillars this spring is attributed to fungal and viral infections this 12 months. However a separate fungal outbreak final fall additionally could have helped regulate populations by means of making some caterpillars carriers of the fungus.
The “zombie caterpillars” inflamed by means of a fall fungus continuously are living lengthy sufficient to hold it again to the outside of the wintry weather webs sooner than death.
When the surviving caterpillars emerge from their wintry weather webs, they are able to transform inflamed by means of the fungus by means of crawling over the inflamed caterpillars that died within the wintry weather webs.
Schmeelk mentioned there are encouraging indications that the fungus outbreaks helped regulate populations this spring, with vital outbreaks seen in Brunswick, Freeport, Durham, Waterville, Richmond, Outdated The city and different spaces.
“For sure some areas skilled aid this 12 months,” Schmeelk mentioned.
A browntail moth caterpillar infestation in a chokecherry tree in Brunswick. Shawn Patrick Ouellette/Personnel Photographer
Become independent from the year-to-year climate prerequisites that may lend a hand the fungus curtail browntail moth populations, the moths additionally have a tendency to be in a “boom-bust” cycle, with a “growth” generally lasting 10-12 years. Maine is recently within the 9th 12 months of the “growth” cycle.
Angela Mech, assistant professor of woodland entomology for the College of Maine, mentioned she is also seeing some reviews that the fungus has been efficient this 12 months. Mech and a crew of scholars had been learning the browntail moth for years, together with whether or not environmentally pleasant pheromone therapies can paintings to regulate populations.
“There have been various spaces out by means of us in Orono that for sure noticed the results of a spring caterpillar mortality match, in lots of circumstances, by means of the fungus. Bushes that had dozens of wintry weather webs on them at first of spring had slightly any defoliation by means of early June, once we would have anticipated to peer a large number of feeding,” Mech mentioned.
Schmeelk mentioned to attenuate browntail moths from laying eggs in your assets, reduce the quantity of outside lighting you placed on at evening, because the moths are drawn to the lighting.