Application of imidacloprid (Merit and other brand names) and other systemic insecticides is effective in controlling Japanese beetle adults. Although the imidacloprid occasionally doesn't work in a tree to control this pest, it does over 80 percent of the time. However, a soil application of imidacloprid typically takes 6-8 weeks to move completely up to the leaves of large trees. With Japanese beetle emergence typically starting the fourth week of June in our area, time is quickly passing to achieve control in that manner. This would be a prime option for linden trees, crabapples, rose bushes, and other favorites of the Japanese beetle.

Imidacloprid can be soil-applied either as a drench or by injection. Because imidacloprid is easily tied up on organic matter, mulch and other dead organic matter must be removed from around the base of the tree before a drench application is made. Removal of turf around the tree would also be recommended for a drench. Soil injections should be made deep enough to get below mulch, turf thatch, and other organic matter, but not deeper than 3 to 4 inches. Apply to the soil within 1 to 2 feet of the trunk, where the greatest concentration of fine feeder roots is located.