Purdue News
Purdue News
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July 16, 2001 Japanese beetles here early, more weeks of damageWEST LAFAYETTE, Ind. – Japanese beetles have emerged in Indiana two weeks early this year and are aggressively defoliating trees, shrubs, flowers and crops, says Tim Gibb, a Purdue University entomologist. Japanese beetles feed on close to 300 different plant varieties. In particular, they like deciduous trees and shrubs such as linden, sassafras, sycamore, Norway maple, birch, elm and flowering fruit trees. Trees or plants that are stressed from being transplanted are particularly susceptible to damage, Gibb says. The beetles also feed on most flower blooms and prefer roses. Gibb says the beetles will mate after they feed on leaves and flowers. In grassy areas, females will lay eggs in early August that hatch into white grubs. The grubs feed on the roots of home lawns during August, September and October, sometimes killing large sections of turfgrass. "Treating beetles as they emerge from your lawn will not prevent plant defoliation because adult beetles fly long distances to find suitable plants to feed on," Gibb says. "In reality, very few of the beetles feeding on your trees and flowers actually originated from your lawn. Controlling adult beetles on trees and shrubs will do little to prevent grub damage." Gibb recommends that adult beetles and grubs be treated separately. If Japanese beetles are causing heavy injury now, an insecticide should be applied. "To get the best control, apply a foliar spray at regular intervals," he says. "Carbaryl (Sevin) is commonly used and provides about seven days of control." Homeowners also might try Malathion or a new material, pyrethroid. Since adult beetles are out earlier, eggs will be laid and hatch sooner as well. If homeowners want to get a head start on grub control, they can apply insecticides such as Merit, Meridian or Mach 2 during July to prevent insect damage, Gibb says. "An insecticide with bendiocarb, diazinon, trichlorfon or isofenphos can be applied later as ‘rescue treatments’ for grub control," he says. "This means the chemicals work if applied after the grubs have hatched, usually the end of July or the first part of August, depending on where you are in the state." Japanese beetles also may cause serious damage to corn and soybeans. Adult beetles may feed on corn silks and interfere with pollination, Gibb says. "If beetles are feeding on corn silks, an insecticide should be applied only if silks are being cut off to less than one-half inch before 50 percent of pollination has taken place," he says. "Don’t rely on how many beetles there are per plant to decide if control is needed. "With soybeans, if defoliation is greater than 40 percent before blooming, greater than 15 percent from blooming to pod fill or greater than 25 percent from pod fill to harvest, an insecticide is needed." Damage to small fruits and vegetables may be prevented by using chemicals such as Sevin, Malathion or Imidan, Gibb says. These treatments must be applied on a regular basis. Caution must be taken to be sure the recommended time on the label expires before harvest. Gibb says all insecticides should only be applied according to label directions. Japanese beetles are normally around for six weeks; however, the pest may be here for close to eight weeks this year. Gibb says warmer temperatures earlier this year drove the beetles out sooner. Source: Tim Gibb, (765) 494-4570, gibbs@purdue.edu Writer: Jennifer Doup, (765) 494-6682, jdoup@aes.purdue.edu Purdue Ag Communications: (765) 494-2722; Beth Forbes, Ag News Coordinator, bforbes@aes.purdue.edu; https://persephone.agcom.purdue.edu/AgCom/news/ Related Web site: Purdue News Service: (765) 494-2096; purduenews@purdue.edu
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