If Merit is to be used, it must be applied before August 1 to be effective. If grubs are present and need to be treated, Diazinon granules can be used on home lawns in mid August-mid September or in late April to reduce the population. Commercial landscapers and golf courses may use Dylox, Proxol or Turcam. Baited traps are effective tools for detection of Japanese beetle to determine first emergence or presence in an area with a low population. Trapping is not a recommended control method.
Traps can only be effective as a control mechanism if they are used in high concentrations.
Use of traps will generally attract many more beetles from the surrounding areas. The grass under where the traps are placed and susceptible shrubs and trees near the traps will often be damaged worse than if they were not used. This article was adapted from various references at the MSU Extension office. If you have any questions please contact the MSU Extension Office.