Answer: You'll need a 2-prong approach for controlling Japanese beetles in your vegetable garden; one for the grubs (next year's population) and one for the adult beetles (this year's population). There are some organic products on the market:
Treat with a combination of Milky Spore and NemaSeek beneficial nematodes in either the spring or the fall. The nematodes help to distribute the Milky Spore. This combination of organisms also works synergistically to most effectively control the grubs. Milky Spore only has to be applied once.
If your larval infestation is severe, apply Grub Beater as well. The active ingredient (neem) is not harmful to either beneficial nematodes or the bacteria in Milky Spore.
Treat again with NemaSeek Beneficial Nematodes six months after your first application to further distribute the Milky Spore and to eliminate newly developing grubs.
Adult Beetle Control
Direct spray applications of insecticidal soap will kill Japanese Beetles on contact but does not provide any residual protection. Pyrethrum is the best organic insecticide treatment against Japanese Beetles.
Large Area Beetle Control: Use PyGanic EC 1.4. This is a pyrethrum concentrate that is effective against hundreds of insects, including the Japanese Beetle.
Small Areas and Garden Beetle Control: Use Safer BioNeem or Bon-Neem (a combination of insecticidal soap and Neem oil) However, please keep in mind that Neem can be damaging to plants that are herbaceous or "sensitive," and in those situations, you would have to use a Pyrethrum.
And, to answer the last part of your question, garlic is one of the ingredients in products designed to deter deer.
Good luck with your garden!
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