Q: In preparation for the inevitable onslaught of the dreaded Japanese Beetles, I was wondering whether you had any thoughts regarding spreading beneficial nematodes?

Is it a better option than milky spore which takes years to work properly? I realize nothing is 100% successful but I hate to spray and harm the bees, lizards, mantises etc.

A: My main concern with using Milky Spore or nematodes is that it takes a while to get control in a landscape, a couple of years in both cases.

And while the grubs in the lawn may be killed, any beetle within 100 yards can easily fly to your susceptible plants.

In other words, you may not see any decrease in adult Japanese beetle numbers for a couple of years…and if no one else in the neighborhood is treating for them I’m not sure you’ll EVER see a decrease.

The Heterorhabditis nematodes seem most effective, but must be applied when the grubs are small – in August or Sept. Be sure to irrigate both before and after application.

See:
Japanese Beetle Control

Pest Control with Nematodes