Has there been any improvement in the technology for controlling Japanese beetles? We have rosebushes and a large grapevine, and by August we are inundated with Japanese beetles. When my father had them, it was our daily duty to pick them off and put them in a can of kerosene.
Swanzey, New Hampshire
Your father had the right idea by collecting Japanese beetles every day, because it stops signals given off by feeding beetles that attract more beetles: Handpicking can reduce overall feeding by half. Soapy water will work as well as kerosene. First thing in the morning, hold it under the leaf or bough where the beetles are feeding, and brush them down into it with your hand. The beetles won’t bite you, and as long as temperatures are cool they will fall into the water rather than fly away.
Other organic pest control measures include applying beneficial nematodes or milky spore disease to lawns to kill white grubs (Japanese beetle larvae), and growing plenty of flowers that provide nectar for Typhia miniwasps, which attack the beetles.
Research shows that commercial traps often attract more Japanese beetles than they catch, so they should not be placed near cultivated plants.