The Q&A Archives: Japanese Beetles

Question: I have vegetables that are ready to eat but Japanese beetles have infested the garden. how can I control them with a spray that will kill the beetles and I still can eat the vegetables? Will rotenone or pyrethrins kill them and can I still eat the vegetables?

Answer: Rotenone is a nonselective, slow-acting nerve poison that paralyzes insects after they eat it. It is highly toxic to most beetles and other insects with chewing mouthparts. It breaks down in about one week when exposed to air and sunlight. It's nontoxic to humans, as are pyrethrin products. For future reference, Japanese beetles are a difficult pest to control. Your best bet is a two-prong approach: one to deal with the larvae, one to deal with the adults.

Japanese beetle grubs are best controlled by spraying beneficial nematodes on the lawn and garden area. These microscopic worm-like creatures attack only the grubs in the soil and not plants, animals or humans. Spray them in spring when the temperatures are above 55F. You can buy the beneficial nematodes from Gardeners Supply, 128 Intervale Rd., Burlington, VT 05401 800-863-1700

For adult beetles, I'd try a new product called whole neem oil. This is different than standard Bioneem in that it is a stronger concentration of this organic spray. It's available from Greenlight Co., Box 17985, San Antonio, TX 78217, 210-494-3481.

I would avoid using those Japanese beetle traps. In some cases, it appears that they actually draw beetles to them from the surrounding area--and you don't need to be attracting extra beetles!

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