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Perhaps it’s not a bad thing that Luzerne County didn’t participate in the state’s gypsy moth control program this year.
If history is any indicator, allowing the population to “boom” one year may cause it to crash the next.
That’s the way Wilkes University biology professor Ken Klemow sees it. The cost to spray for gypsy moths isn’t money well spent, he said, advising it’s best to bite the bullet for a year, let the invasive pests go through their life cycle and it should crash the following year.
That’s what happened during an infestation in the late 1980s that Klemow said was even worse than the current event.
“Back in 1988 just about everything was defoliated in the forests and it was real scary. It looked like January in July,” Klemow said. “The thinking was the forests wouldn’t recover, but they did pretty well the following year and some trees even put on new growth that same year.”
In 1988, Klemow said, a state forester advised against spraying and recommended that the gypsy moths be allowed to go through their cycle and there won’t be a problem for years. Klemow said that’s exactly what happened as the caterpillars basically devoured their entire food source and the population bottomed out.
In his experience, Klemow said during years of gypsy moth population booms he has seen dead caterpillars hanging from the remnants of devoured leaves. Those caterpillars aren’t making it to the pupa and adult stages, and they likely died from starvation, a virus that is common during population explosions or from either fungus or bacterial infections.
“If you do use control measures, the population is knocked down but the next year those larvae blow around and they’ll come back. The problem could get even worse,” Klemow said, adding research suggests that spraying doesn’t kill entire populations.
Now that much of the area has endured this year’s gypsy moth infestation, here’s a look at the impacts for the rest of the year and long-term:
Will trees that were defoliated this year die? Klemow said unless there are repeated years of infestation, the trees should be alright. But there’s still risk. During the course of the year, trees are producing sugars via photosynthesis that are stored in the roots for the winter. In the spring, Klemow said, those reserves are brought up into the stems to produce leaves, flowers and fruit. “The problem now is the tree is missing out on an opportunity to photosynthesize and the roots won’t have as much nutrient reserves during the winter,” he said.
What are the chances that trees will produce new leaves this year? “Pretty good,” Klemow said, as long as there aren’t other stress factors such as drought involved. Klemow remembers trees producing a second growth of leaves during the 1988 infestations. “In September it might look like May with smaller, lighter green leaves.”
Nick Lylo, district forester with the state Bureau of Forestry, said if trees re-leaf it generally occurs after July 4.
Will defoliated oak trees still produce acorns this fall? Wilkes University biology professor Michael Steele, who has done extensive research on acorn production and dispersal, wasn’t too optimistic that oaks will be dropping acorns this year. Steele said this year’s gypsy moth outbreak is the worst infestation he’s witnessed, and he suspects the defoliation will force oaks to direct their energy away from acorn production as the trees try to re-foliate.
“Many of the white oaks have been completely defoliated but they are now sprouting new leaves. Regardless, I expect this year’s crop to be aborted by white oaks,” Steele said.
Red oak acorns take two years to develop so while red oak trees may abort this year’s crop, next year’s production should be back to normal, according to Steele.
“Overall I would expect a mast failure this year, but we should know better by August is acorns are aborted in big numbers,” he said.
With the tree canopy gone and more sunlight reaching the forest floor, will young trees benefit this year? Klemow said they will, but if the canopy comes back next year the growth of the young trees will slow back down. He added that the boost from additional sunlight this year could make the robust vegetation on the young trees more appealing to deer.
Do a lot of counties statewide participate in DNCR’s spray program? Not really. According to Tim Marasco, field operations supervisor with the Bureau of Forestry, one county (Carbon) participated this year and only three (Venango, Clearfield and Crawford) signed up in 2014. Marasco said infestations tend to be regional, not statewide, which is reflected in the geographic locations of those counties who choose be a part of the spray program. In the last 15 years, the highest number of participating counties in a given year was 21 in 2008.
Will the stress from this year’s defoliation be reflected by a narrower growth ring in trees? That’s what Klemow expects. This summer he’ll be examining growth rings on trees to determine if the 1988 infestation can be identified.