The annual fight against gypsy moths, whose caterpillars can defoliate oaks and other trees, is set to begin next week in DuPage County's forest preserves.
Forest preserve officials say the Illinois Department of Agriculture is expected to spray for the moths beginning June 30 in the southeastern and northwestern parts of the county. The list of forest preserves expected to get treatments include Waterfall Glen near Darien, Pratt's Wayne Woods Woods near Wayne, West DuPage Woods near West Chicago and Hawk Hollow near Hanover Park.
DuPage has been battling gypsy moths, which aren't native to the area, since the 1980s. But what started as very small, occasional outbreaks became a major fight in the early 2000s when the county was enveloped by the front line of invading gypsy moths, forest preserve officials said.
"With the tools we have available to us today, we cannot eradicate gypsy moths," said Tom Velat, the district's invertebrate ecologist.
So the goal of the treatments will be to minimize the damage the insects can do by trying to suppress their populations. In addition to forest preserves, the treatment area will cover thousands of acres of private and public land in northern Illinois, officials said.
The state will use small planes flying roughly 100 feet above the treetops to spread green rice-sized flakes that contain gypsy moth pheromones, chemicals the females produce to attract males, officials said in a news release.
Velat said flakes prevent male moths from reaching females and successfully mating.
"It confuses the male into mating on inanimate objects where the flakes fall," Velat said, "or it confuses them so they don't know exactly where the females are because there's this cloud of pheromone that they're completely surrounded by."
If gypsy moth populations aren't controlled, it could be devastating for oaks and other trees. A large number of gypsy moth caterpillars can completely defoliate an entire tree within one season.
"That limits the tree's ability to photosynthesize and transport nutrients around the tree," Velat said. "So that severely weakens the tree."
Trees start to die after two years of complete defoliation.
The flakes used in the treatments only target gypsy moths. They don't contain pesticides and are nontoxic to other wildlife and humans. While the flakes may stick to vehicles or pavement, they should wash off, officials said.
The starting date for the treatments is weather-dependent.
Meanwhile, DuPage's forest preserves will remain open for normal operating hours, one hour after sunrise until one hour after sunset.
For more information, visit the Illinois Department of Agriculture's Facebook page at facebook.com/GypsyMothIllinois.