Post by wvhsparent on Jul 22, 2008 8:05:39 GMT -5
University of Illinois Extension
DuPage County
1100 E Warrenville RD – Suite 170
Naperville, IL 60563
630-955-1123
www.extension.uiuc.edu/dupage
July 22, 2008
News Release From: Barbara A. Linek - County Director
PLEASE RELEASE IMMEDIATELY
Japanese Beetles on Landscape Plants In Northern Illinois
Only a few years ago, Japanese beetles were something talked about as a potential problem in the future. Now, they are present in northern Illinois in field crops and on landscape plants. "Japanese beetles are one of the exotic insects that have made their way into the United States and wreak havoc due to the lack of a natural predator," says David Robson, University of Illinois Extension horticulture educator." And unlike most insects, both the adult and larval stages can cause major injury."
Adult Japanese beetles are between 1/4 and 1/2 inch long. They're easily identified because of their metallic green body with coppery wings. On either side of the wings are five tufts of white hairs.
The larval stage is one of the three major grubs that feed on turfgrass, though not yet in the numbers as the annual white grub from the June beetle or masked chafer. Beetles mate in June, and the female lays eggs in early July. Eggs hatch out in August, and grubs continue to feed and grow until they pupate in April or May. Most Japanese beetles start emerging from the ground in late May. There is only one generation per year, but the adult stage can be present until early fall.
Adult Japanese beetles are voracious feeders, especially on sunny days, and seemingly indiscriminate. Like most insects, they have their favorite food but will feed on anything present. It was initially thought that beetles would feed for only a month or so, following a similar life cycle as June bugs. However, reports indicate Japanese beetles feeding into September, though numbers were drastically reduced.
"Roses, grape vines and linden trees seem to be the favorites in Illinois," says Robson. "The Japanese beetles do not discriminate–all types of roses and lindens are fair game, even the supposedly insect- and disease-proof shrub roses. You can find the insects on viburnums, climbing hydrangeas, Shasta daisies, daylilies, porcelain vine and some fruit trees." Generally, the beetle feeds on the tender upper leaf tissue between the veins, creating a skeletonized look to the leaf. In many cases, what's left turns brown, giving the plants a scorched appearance.
Robson says large holes can be munched out of flowers, and occasionally you will find damage to fruits and vegetables, though vegetables tend to be one of the last things the beetles will eat. Most summer Illinois fruits, such as apples, peaches and pears, have a skin that is harder for beetles to digest.
Control is difficult. Beetles may fly miles from where they emerge. Complicating matters is the fact that in early July the creatures will take flight when disturbed; as they mature, they become easier to pick off or knock off the plants.
Adults can be controlled by knocking into containers of hot, soapy water. These efforts will probably need to be repeated daily for several weeks. Start as soon as possible.
Netting can be used to cover some prized plants, but make sure there are no beetles under the net when you apply it.
Japanese beetle traps have shown effectiveness, though reports indicate that they actually attract more beetles into the yard that may not be caught by the traps. The current recommendation is to not use traps at all, or to place them at least a city block or more from your yard.
There are several insecticides that can be used as knockdown sprays. The insecticide carbaryl, often sold as Sevin, provides some of the best control. More than likely, you will have to repeat applications every five to seven days. Other products include acephate (Orthene) and cyfluthrin (Tempo). Imidacloprid (Merit) is often sold as Japanese beetle control, but it is a systemic, which means it must be applied early in the season, usually early May, to allow the plant to absorb it.
Be sure to read and follow directions, locating "Japanese Beetle" control on the label.
Grubs can be controlled with imidacloprid (Merit) or Milky Spore disease, a bacterial toxin that will only have an effect on the Japanese beetle grub.
Above all, maintain the health of the plant. Plants damaged during the summer are more likely to suffer from reduced leaf surface that reduces sugar production. Plants may grow less and have a more difficult time recovering from stress conditions such as drought, early frosts, diseases and other insect attacks.
Plants will often recover and appear fine next year, living on stored food reserves. But, repeated defoliation in early summer will weaken many trees, shrubs and vines.
Keep plants watered and properly fertilized. Contact your local U of I Extension office at 630-955-1123 for more information on maintaining plant health, or visit www.extension.uiuc.edu/.
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Source: John Church, University of Illinois Extension Educator, Natural Resources, Rockford Ph. 815-397-7714