Answer: 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 temerpatures are above 55F and you should see a difference this summer. You can buy the beneficial nematodes from, Gardeners Supply co, 128 Intervale Rd. Burlington, VT 05401 800-863-1700.
Another approach is the botanical Rotenone. It's 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 adult beetles, I'd try a new product called whole neem oil. This is different than the 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.
Tree borers are a challenge to combat, since they are protected within the tree trunk and branches. You can take a stiff wire and work it into the borer holes to poke them to death, or inject parasitic nematodes into the holes. Prune off branches that are badly infested, and give the tree plenty of TLC - moderate watering and feeding - to keep it as healthy as possible. Hope this helps!
Q&A Library Searching Tips