Purdue News
Purdue News
July 12, 1996
According to Tim Gibb, an entomologist for Purdue University's Cooperative Extension Service, the iridescent green and gold bugs are destructive as adults and as immatures.
"As immatures, known as white grubs, Japanese beetles feed on turfgrass, and as adults they damage ornamentals, trees, flowers, and crops such as corn and soybeans," Gibb said. "Once people see them eating their prize rosebush, they are not likely to forget them."
Gibb said Japanese beetles, unlike most other insects, feed at night and during the day, so they sometimes can be caught in the act of turning prize rosebushes into lunch.
The Japanese beetle population has been fairly large the past few years, so Gibb is expecting another large, problem-causing crop this summer. The Japanese beetle is not a finicky eater, and Gibb said that almost any plant in a garden can fall victim to its voracious appetite.
"The beetle will feed on lots of different plants," he said. "Many insects will feed on two or three types of plants, but the Japanese beetle will eat almost 300 different plants. It particularly likes roses, linden trees, flowering crabapples and flowering plum. Almost anything green is susceptible to damage."
The emergence of the Japanese beetle also begins the mating season. During the end of July and the beginning of August, the females lay eggs in the ground. Less than a month later, white grubs emerge and begin feeding on turfgrass. Homeowners concerned with turfgrass damage may use insecticides to control the white grubs as they hatch, Gibb said.
Adult Japanese beetles can be controlled with the insecticide Sevin (carbaryl), but Gibb recommended that homeowners reapply the insecticide according to label instructions because of the sheer numbers of beetles emerging.
Gibb also advised against several methods that have been publicized to remove Japanese beetles. The common beetle traps that release floral scents and pheromones (aromatic hormones) to lure beetles only succeed in attracting more beetles to the area, he said.
"They can attract beetles from hundreds of yards away, from all of your neighbors' yards. If there are any susceptible plants in the area of the trap, the beetles will stop off and feed on that on the way to the trap," Gibb said. "The only way to get beetle traps to work for you is to hope your neighbor gets one."
Another publicized way to remove the beetles is to puree a couple of cups of the beetles in a blender and spread the mixture on plants. Gibb said this method may have the same effect as the traps.
"Japanese beetles don't have the alarm pheromones that some insects do, and this might release sex pheromones from the females that will just attract more male beetles," he said. "And besides, it will make one big stinking mess."
Additional information about the Japanese beetle and its control is available in Extension Publication E-75, "Japanese Beetles," available for 50 cents at county offices of the Purdue Cooperative Extension Service.
CONTACT: Gibb, (317) 494-4570; Internet, t_gibb@acn.purdue.edu
cs/agroundup/9607f5
Compiled by Chris Sigurdson, (317) 494-8415; home (317) 497-2433; Internet, sig@ecn.purdue.edu
