Tom Schmeelk, an entomologist with the Maine Forest Service, factors out the place feeding injury from browntail caterpillars is obvious on the leaves of a northern purple oak sapling. A fungus knocked again populations of browntail moths this spring, though scientists should not positive by how a lot. Ben McCanna/Employees 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 annual struggling attributable to the tiny hairs they launch into the air.
However it’s too early to know whether or not the fungus will assist spur a statewide inhabitants collapse of the forest pest or if that is the beginning of a protracted break within the yearslong infestation that has unfold alongside the coast and inland.
Microscopic hairs from the caterpillars could cause a particularly itchy, lingering rash in individuals, usually from Might to mid- to late June, earlier than the grownup caterpillars pupate and rework into moths. Along with a rash, signs can embrace respiratory issues, together with issue respiratory and irritation of the lungs and throat.
There isn’t any knowledge that will present how many individuals expertise these signs, however potential publicity to the microscopic hairs is linked to how sturdy the inhabitants of browntail moth caterpillars is annually.
Thomas Schmeelk, an entomologist with the Maine Forest Service, stated the climate this spring created “Goldilocks” situations for the fungus to proliferate and kill the caterpillars – not too dry and never too wet. A virus that kills the caterpillars – additionally tied to climate situations – has additionally contributed to lowering browntail moth populations.
“Now we have many experiences of the fungus and the virus all through the infested areas of the state, and it’s a reasonably broad swath. It’s an excellent signal. We’re hopeful that is the start of the top for this outbreak (of browntail moths),” Schmeelk stated.
Whereas rain helps develop the fungus, an excessive amount of rain, just like the constant wet situations in spring 2023, suppresses the proliferation of the fungus, which made it much less efficient in controlling browntail moth populations final spring, he stated.
However this 12 months, periodic heavy rainstorms have usually been adopted by a number of days of dry climate, which has helped to disperse the fungus, Schmeelk stated. Spores from the fungus – entomophaga aulicae – want a break within the moist climate in order that wind can carry them to different areas to contaminate extra caterpillars.
Tom Schmeelk, an entomologist with the Maine Forest Service, scans a bunch of northern purple oak saplings for pupal packets the place feeding injury from browntail caterpillars is obvious. Ben McCanna/Employees Photographer
Schmeelk stated an aerial surveillance of leaf cover this August and September will assist to quantify the vary and density of a brand new crop of browntail moth caterpillars that might be rising from eggs this summer season and later overwinter of their winter webs.
The quantity that the newly emerged caterpillars eat this summer season ought to assist decide how efficient the fungus was in killing the grownup caterpillars this spring. Browntail moth caterpillars are likely to feed on leaves of fruit, oak, birch, elm and poplar bushes.
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 might have helped management populations by making some caterpillars carriers of the fungus.
The “zombie caterpillars” contaminated by a fall fungus usually dwell lengthy sufficient to hold it again to the outside of the winter webs earlier than dying.
When the surviving caterpillars emerge from their winter webs, they will turn into contaminated by the fungus by crawling over the contaminated caterpillars that died within the winter webs.
Schmeelk stated there are encouraging indications that the fungus outbreaks helped management populations this spring, with vital outbreaks noticed in Brunswick, Freeport, Durham, Waterville, Richmond, Outdated City and different areas.
“Actually some areas skilled reduction this 12 months,” Schmeelk stated.
A browntail moth caterpillar infestation in a chokecherry tree in Brunswick. Shawn Patrick Ouellette/Employees Photographer
Separate from the year-to-year climate situations that may assist the fungus curtail browntail moth populations, the moths additionally are usually in a “boom-bust” cycle, with a “growth” usually lasting 10-12 years. Maine is at present within the ninth 12 months of the “growth” cycle.
Angela Mech, assistant professor of forest entomology for the College of Maine, stated she is also seeing some experiences that the fungus has been efficient this 12 months. Mech and a group of scholars have been finding out the browntail moth for years, together with whether or not environmentally pleasant pheromone therapies can work to manage populations.
“There have been a lot of areas out by us in Orono that positively noticed the results of a spring caterpillar mortality occasion, in lots of circumstances, by the fungus. Timber that had dozens of winter webs on them in the beginning of spring had barely any defoliation by early June, once we would have anticipated to see loads of feeding,” Mech stated.
Schmeelk stated to attenuate browntail moths from laying eggs in your property, decrease the quantity of outside lights you placed on at evening, because the moths are interested in the lights.
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