Purdue News
Purdue News
|
|
June 29, 2004 Japanese beetle arrivals are early and numerousWEST LAFAYETTE, Ind. – Homeowners and gardeners beware: Japanese beetles are ahead of schedule this year. "Throughout the state, Japanese beetles are early," said Tim Gibb, a Purdue University Cooperative Extension Service entomologist. "They're anywhere from 10 days to two weeks early this year.
"The real glitch is not only that they came out early this year, but also populations appear to be much higher than normal, so it's going to be a double whammy." Gibb attributes the early arrival to the warm spring, which helped urge beetle development. "Insects develop in direct proportion to the amount of heat that they get over a year's time," he said. This means that homeowners, gardeners and farmers should already be watching for signs of the beetle. "We're going to be in the middle of Japanese beetle damage much more early this year," Gibb said. Because of the high populations, beetle damage could be more intense. Japanese beetles are especially fond of roses, shrubs, flowering fruit trees and deciduous trees such as linden, sassafras, sycamore, Norway maple, birch and elm. They also feed on corn silks and soybean foliage. If a plant, tree or yard was infested with Japanese beetles before, chances are it will be again, because the beetles tend to return to the same areas year after year. "There are certain plants that Japanese beetles will go to every year and they will wreak havoc there," Gibb said. "Those particular plants need to be treated several times throughout the year." Other plants only get hit when the beetle population is high. "What we recommend is that homeowners watch very closely, treat when necessary, and be prepared to treat again after that residual wears off," he said. Chemical treatment recommendations depend as much on the plant as the beetle. Foliar insecticide sprays, such as Malathion or Sevin, or newer synthetic pyrethroids, can be applied to larger plants and trees. Gibb said Sevin provides seven days of control, while pyrethroids, sold under a variety of trade names, may work for more than two weeks to ward off beetles. These materials should contain one of the following active ingredients: permethrin, esfenvalerate, cyfluthrin or bifenthrin. All insecticides should only be applied according to label directions, he said. For small plants, such as roses, vegetables and bushes, Gibb said the beetles can be picked off on a daily basis and dropped into a container of soapy water. Japanese beetles mate while feeding on flowers and leaves. During July, females lay eggs in turfgrass that hatch into white grubs in early August. This makes July a good time to apply preventative insecticides such as Merit and Mach II for grub control, but Gibb cautions homeowners against assuming they need to apply chemicals for grubs. "Studies show that many grub control applications are wasted because grubs were never present in the first place," Gibb said. "Apply controls only if a history of grub problems warrant application, or if sampling the soil indicates five or more grubs per square foot." White grubs feed on turfgrass roots and are especially fond of well-maintained lawns. They prune the roots and reduce moisture and nutrient absorption, causing small, irregular circles of grass to wilt and eventually turn yellow or brown. "If you see these symptoms, walk on it. If it feels a little more spongy than normal, that's a good indication to dig down and look for grubs," Gibb said. If grubs are present, then chemical treatment is in order. Prior to mid-August, insecticides like Merit and Mach II are appropriate. "Once it gets past mid-August, we recommend going with a different chemical, like Dylox or Proxol," Gibb said. At that time the chemical needs to treat existing grubs rather than prevent them, he said. More information about insecticides and plants resistant to Japanese beetles is available online. Writer: Kay Hagen, (765) 494-6682, kjh@purdue.edu Source: Tim Gibb, (765) 494-4570, gibb@purdue.edu Ag Communications: (765) 494-2722; Beth Forbes, forbes@purdue.edu Related Web sites: PHOTO CAPTION: A publication-quality file photo is available at https://www.purdue.edu/uns/images/gibb.beetle.jpeg
|
