Japanese Beetles Have Invaded Northeast Oklahoma

The Japanese beetle (Popillia japonica) has been highly visible in northeast Oklahoma this summer.  It feeds on approximately 300 plants and consumes leaves, flowers and overripe fruit.  The tree species that the adult beetle feeds on includes birch, elm and crabapple.  Leaves are left with a skeletonized appearance. 

This beetle was first introduced into the United States from Japan around 1916 when it was reported in New Jersey.  It has been spreading westward since that time and in recent years has reached Oklahoma.  The beetle is currently found in approximately ten counties in the state with the heaviest infestations in the northeast.

The adult Japanese beetle is 3/8 inch long and 1/4 inch wide making it approximately half the size of the June beetle for which it is occasionally mistaken.  The body is metallic green with bronze wings.

The beetle feeds during the day and prefers plants located in the sun.  Handpicking the beetles in the mornings and evenings while they are moving slower can be an effective means of control.  Beetles that are feeding attract more beetles so capturing the early scouts is important.  The beetles can easily be killed by dropping or knocking them into a solution of soapy water.  Dousing plants with soapy water in the morning is also an option.

The effectiveness of Japanese beetle traps is questionable.  It is widely believed that traps attract more beetles than they catch since adult beetles can fly a mile or more.  If traps are used they must be distributed around the perimeter of a wide area, perhaps an entire community.

Insecticides labeled for Japanese beetle control are readily available and can be effective.  Sprays may have to be applied weekly when beetle activity is heavy.  Always read all label directions before applying any pesticide.