Purdue News
Purdue News
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February 18, 2000 Gypsy moths threaten oak trees in BroadrippleWEST LAFAYETTE, Ind. – This spring gypsy moth caterpillars could start stripping all the leaves off the oak trees around Broadripple if the Indiana Department of Natural Resources doesn't spray, says Purdue University entomologist Cliff Sadof.
Sadof will describe the gypsy moth invasion and treatment options at a Purdue Cooperative Extension Service program at 1:50 p.m. March 11 as part of Marion County's Extension Spring Gardening Clinic at Harshman Middle School, 1501 E. 10th St., Indianapolis. Sadof's talk is free, although he requests preregistration. Over the past few years, gypsy moths have eaten their way down from Michigan into the top tier of Indiana counties. The line of infestation stops about 100 miles north of Indianapolis. However, some egg masses or female moths skipped over the line, directly into the state capital, probably by hitchhiking a ride on firewood, Sadof said. From those first hitchhikers, the moths have spread through a 551-acre area around Broadripple in the northern part of Indianapolis and into a 564-acre site just south of Zionsville along State Route 421. "If we have another dry spring, they could start creating havoc on plants like the oaks along Meridian Street," Sadof said. "Large, older caterpillars can eat all the leaves off a tree in a matter of days." Oak trees are a gypsy moth favorite, although the bugs will eat any of 500 different plant species. While healthy trees will send out a second flush of leaves after the first leaves are eaten, three or four consecutive years of defoliation can be deadly. The moths can also make life unpleasant for people, Sadof said. People living in heavily infested areas sometimes develop allergies to the caterpillar hairs and suffer from skin or eye rashes. "Plus, under really infested trees, the ground, chairs or picnic tables get covered by caterpillar droppings and smelly, diseased caterpillars," Sadof said. The caterpillars hatch from eggs in late April, feed on leaves until June, then go into a kind of hibernation until they turn into moths in July. The moths then mate and lay the eggs that produce the next year's generation. If the state Department of Natural Resources acts this year, Sadof said, it could eliminate the moths and stave off the invasion for another five years. That might buy researchers enough time to come up with alternative and better controls. There are generally two choices for controlling the gypsy moths, Sadof said – insect pheromone flakes to control the moths during the summer, when they are mating, and the Bacillis thuringiensis (Bt) protein to control the caterpillars in the spring, when they are eating tree leaves. The DNR will probably use pheromone flakes, Sadof said. In nature, female moths produce pheromones, substances that act like powerful perfumes to attract mates. By spreading flakes of the pheromone when adult moths emerge in an infested area, male moths search out flakes instead of females, don't mate, and the population plummets. Pheromone flakes are safe. In fact, since the DNR would apply only 1 cup per acre, residents would be hard-pressed to find a flake after application. The pheromone flakes are coated with a thin glue, and most of them will stick like little Post-it Notes to leaves in treetops. No problems were reported last summer when a similar application was made over full parking lots at the Indiana Dunes. Bt, the other treatment option, is safe and controls the caterpillars just as well as pheromone flakes control the moths, Sadof said. In fact, the DNR plans to use Bt to control gypsy moths at three other Indiana sites this year. Bacteria produce the Bt protein to kill caterpillars that then become food for them. It only affects caterpillars. The Bt protein is sold in crystal form for spraying on plants that are threatened by voracious insects. The Bt crystals dissolve in caterpillars' guts and damage their stomachs so that they stop eating and die. Bt is harmless to humans, Sadof said. "In the Northeast they've been spraying areas with Bt since 1961 and haven't seen any ill health effects," he said. However, a Bt spray will kill all types of butterfly and moth caterpillars in the sprayed area. Fortunately, most Indiana butterflies and moths, including Monarchs, are not in the susceptible caterpillar stage in spring when the DNR would spray. Whether the agency uses pheromones or Bt, Sadof said, he just hopes the DNR treats Indianapolis neighborhoods this year. "In the early stages of invasion, when people don't see a problem, they often say they don't want sprays," Sadof said. "But when the first wave hits and trees get defoliated, people get very upset and want to get rid of the caterpillars with Bt. By then, there's not enough Bt to go around. Then we have to choose which few trees to save with the Bt we've got." A few years after the first wave of gypsy moths takes its toll on the trees, natural enemies will start to keep the insects in check and will lessen the magnitude of the problem, Sadof said. But by then many large trees are dead. To hear Sadof's free gypsy moth talk, preregister by calling (317) 848-7351. It costs $5 to attend the entire Marion County Extension Spring Gardening Clinic, which runs from 8:15 a.m. to 2:50 p.m. at the Harshman Middle School, 1501 E. 10th St., Indianapolis. For more information on gypsy moths, visit the Indiana Gypsy Moth Education Home Page. View a map that outlines the Broadripple area infested by gypsy moths. View a map of the infested area around Zionsville. You can also call the DNR information phone line at (317) 232-4120. Source: Cliff Sadof, (765) 494-5983; cliff_sadof@entm.purdue.edu Writer: Rebecca J. Goetz, (765) 494-0461, rjg@aes.purdue.edu Purdue News Service: (765) 494-2096; purduenews@purdue.edu PHOTO CAPTION: In late April, gypsy moth caterpillars such as these hatch from eggs and climb to treetops where they feed or dangle from strands and are blown to other trees. Each caterpillar can eat 11 square feet of foliage in its lifetime. (Photo courtesy of Michigan State University Extension Service) A publication-quality photograph is available at the News Service Web site and at the ftp site. Photo ID: Sadof.moths
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