Japanese Beetles Are Invading

Author: Mosquito Squad of Waukesha County & Milwaukee North Shore

Small green and copper colored insects will begin hatching across Wisconsin destroying flowers and plants in their wake.

They live in every state east of the Mississippi.  Mild winters and moisture cause them to migrate as far north as Green Bay and Eau Claire.

The beetle has a four week life span.  Adult beetles feed on plants, buds, and flowers leaving patches of damaged plant tissue leading to a plants decline in health.  The adults will breed and then the females look to lay eggs in semi moist to moist soils. Through their various instar stages, larvae feed on grass plant roots limiting the plant to access water leading to a decline in plant health from damaged and weakened root systems. Various animals like turkeys, skunks and raccoons will listen for the feeding of the white grubs in the soil and then dig for that food source causing further damage to the aesthetic lawns.  Here are some options you can do to reduce their population in addition to getting some professional assistance.

  • Handpick beetles off plants and put in a jar of soapy water to discard.
  • Spray insecticidal spray to repel beetles and kill existing ones on contact.
  • Try organic options such as an insecticidal soap or an insecticidal pyrethrin treatment for elimination.
  • Bring in some new plants such as garlic to help discourage these beetles.
  • Control white grub populations through early to mid summer soil insecticidal treatments to eliminate the grubs and doing so at their earliest instar stages is best.

Avoid Japanese pheromone beetle traps.  These catch a lot of existing beetles but tend to attract other beetles to the area.  A trap will bring in more beetles, and beetles that don’t end up in the trap can lay eggs in the area potentially creating more beetles for next year.

USA Today published and released an article in 2017 confirming an increase in these populations last year and some additional tips as well.

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