The Japanese Beetle can be one of the most destructive garden pests, especially on roses, raspberries and linden trees. Late June to the end of July are the prime foliage eating times for the Japanese Beetle adults and one of our clients has spotted them in her garden already.

The Ohio State Extension Fact Sheet lists several options to control or minimize Japanese Beetle damage… these are the two that make the most sense:

Option 1: Cultural Control - Hand Picking

The first Japanese Beetles that arrive in your garden are often “scouts.” They chemically signal other Japanese Beetles to join them at the feast. By noticing when the first adults arrive on a property, you can pick off and destroy these scouts that attract additional pests. The adults are less active in the early morning or late evening. They can be destroyed by dropping into a container of soapy water.

Option 2: Insecticide

The adults can be controlled by spraying susceptible plants with insecticides. Over-the-counter pesticides available for this include: acephate (Orthene), carbaryl (Sevin), and several pyrethroids - bifenthrin, cyfluthrin, deltamethrin, lambda-cyhalothrin, permethrin, and others. Applications of imidacloprid (=Bayer Advanced Tree & Shrub Concentrate) generally need to be made 20 days before anticipated Japanese beetle adult activity. During the heavy adult activity periods, sprays may be needed every 5 to 10 days.

A couple of important notes - there is no “Japanese Beetle” specific insecticide, so the insecticides will kill other insects in the process, some of which may be beneficial in your garden. Also, there is a Japanese Beetle look alike called the False Japanese Beetle. It is more greenish black in color and will not have the distinctive 5 hairy stripes on the side that the Japanese Beetle has.

Tags: pests