Japanese beetle grubs and vegetables they don't like

Asked June 13, 2017, 5:33 PM EDT

I was recently turning the soil in my raised garden preparing for planting and discovered many of the Japanese beetle grubs pictured online. They look a lot like the grubs that destroyed my summer squash plants years ago. I no longer plant summer squash, but now seeing so many grubs I have searched for popular vegetable plants that the grubs do not favor and those they would avoid. I don't know of any pesticides that are safe for a food crop so can you please advise?

Hennepin County Minnesota

1 Response

Thank you for the question. Japanese beetle grubs feed on turfgrass roots, not vegetable roots or plants. The adult beetles are known to eat many different plant leaves and buds. It's possible you found a Japanese beetle grub or some other grub while turning your soil if it was in an area growing turfgrass in the last year or two but the grub itself is not a threat to your squash. Many grubs look very similar. Learn more about Japanese beetles here: https://www.extension.umn.edu/garden/insects/find/japanese-beetles/
There is a pest called the squash vine borer that lives and matures inside the hollow stems of squash causing wilting, rotting, and sometimes death. It does look similar to the Japanese beetle grub but their habits are very different. Read here to learn how to manage squash vine borer with or without chemicals:
Personally, I've had moderate success slitting the vine, fishing out the borer, and letting the plant recover. You will need to scout the plant for the squash borer adult and act quickly to avoid crop loss. Vine vegetables not susceptible to squash borer are winter squash, cucumbers, watermelon and other melons.

It is possible to use the proper insecticide and still enjoy your vegetables but only if you carefully read and follow all directions on the package. It will list wait periods necessary between chemical use and harvest, as well as the vegetables and insects indicated for use.