Japanese beetles are out and about

Spray for Japanese beetles when you first find them on your trees, shrubs and flowers, as the odor of crushed leaves from feeding will attract more beetles.

Japanese beetles are feeding heavily on preferred trees, shrubs and flowers in southern Michigan. On linden trees, the beetles feed most heavily on the tops of trees, turning them into lace. Japanese beetles feed on a wide range of deciduous trees and shrubs, including roses, linden, sassafras, sycamore, pin oak, Norway maple, Japanese maple, pussy willow, birch, elm, canna lilies, raspberries, grapes, beans, Virginia creeper and flowering fruit trees. They will continue feeding and laying eggs throughout July and August. By early September, the beetles begin to die and few can be found after October 1.

After feeding on leaves and flowers, the beetles mate and lay eggs in turfgrass, where they become white grubs that eat turf roots. In order to protect susceptible types of trees, shrubs and flowers from Japanese beetle, spray them with Sevin (carbaryl) or Bayer Multi-Insect Killer (cyfluthrin) when you first find them. Once beetles start feeding on a plant, the odor of crushed leaves attracts more beetles. Spray again every one to two weeks until late August, if necessary.

Japanese beetle traps are a great way to find out if you have Japanese beetles, but they do not prevent plant damage, and many deployments of traps may result in more injury to susceptible plants located near traps.

Dr. Smitley’s work is funded in part by MSU‘s AgBioResearch.

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