Illinois’ weapon in the fight against invasive gypsy moth: fake sex pheromones. Planned spraying in DuPage canned goods | Chicago News

A spongy moth caterpillar. (Feliciano Moya López / Pixabay)

The Illinois Department of Agriculture will spray to control the invasive gypsy moth (Lymantria disparformerly known as gypsy moth) in late June at several locations in northeastern Illinois, including Waterfall Glen, Des Plaines Riverway, Hidden Lake and Wood Ridge Forest Preserves, officials said.

Butterfly caterpillars are voracious foliage eaters, showing a preference for oak trees. During large epidemics, trees can be completely stripped of their leaves in a few days. These weakened trees are more susceptible to other diseases and other pests, which affects their chances of survival, according to the Ministry of Agriculture.

The spray treatment, using what is called a ‘pheromone mating disruptor’, will be applied by a low-flying aircraft, making multiple passes. Officials said the treatment was not harmful to people, pets, other wildlife, plants, cars or structures. Signs will be posted on processing days, which are expected to be June 27 and 28.

The spongy moth was introduced to the United States in the 1860s and after escaping captivity in the Boston area, it has since migrated outward. Northeastern Illinois is now at the western end of the management zone to contain the pest.

There are two common methods of containment, explained Scott Schirmer of the Illinois Department of Agriculture’s Office of Environmental Programs.

One is Btk, a bacterial insecticide that targets feeder caterpillars and kills them. It is applied in April or May, depending on the emergence of the gypsy moth caterpillar and the development of tree foliage, in places where there is a large population of moths in a small area.

“It’s like taking a bucket of water and pouring it over a campfire,” Schirmer said. “You put out the fire before it spreads.”

Mating disruption is the other option, widely used when there is a low level of infestation over a larger area.

Here’s how it works: synthetic sex pheromones are applied in waxy droplets, and the overload of scent overwhelms the males.

“Everything smells like their favorite cologne. They can’t identify the females,” Schirmer said. “It’s not lethal. It’s just there to confuse them.”

Thinking that females are everywhere, males cannot find one to mate with; no mating equals no offspring. The treatment only affects the gypsy moth, not other species of moths or butterflies, according to Schirmer.

The combination of the two treatments has proven to be very effective. Illinois has been able to maintain the line of gypsy moth spread and even push it back at times over the past 30 years, he said.

The department monitors nearly 6,000 traps in the northern part of the state, with the US Department of Agriculture trapping the southern third. The traps are set at the end of May and checked at the end of the summer. The number of moths caught in the traps determines the treatment the following year, according to Schirmer.

“The program is called ‘Slow the Spread’. We know we won’t be able to eradicate it,” he said. “But we can stop it from jumping, say, from Kane County to Rock Island.”

This story was originally published on June 10. It has been updated.

Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]


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