Q. What can I do right now to get rid of Japanese beetle grubs so they won’t attack my plants this summer?
Paul from Youngstown
A. Your plan of attack should simply be preparation. Controlling Japanese beetle grubs in your lawn will NOT control populations because the adults fly around.
While controlling these grubs in the lawn will reduce the grubs’ feeding on the roots of your lawn (if it is that bad), it will not control the thousands of other grubs in other lawns. These other grubs will become the adults that still affect the plants in your landscape.
Japanese beetles have a tremendous sense of smell. They can travel miles to aggregate at the site of their favorite foods. They use pheromones (a scent used for communicating) to tell each other where the good eats are located. Thus, what you need to do is get the first beetles — the scouts — and eliminate them before they can tell the other beetles where your good-tasting plants are located.
You can do this by drowning them in a cup of soapy water.
To do this effectively, you need to know when they will arrive in your yard. Most years, we’ll see the first Japanese Beetles just after the Fourth of July. But this changes year to year based on growing degree days — a measure of our overall warmth of the season. You can put your zip code into the following website around that time to see if the beetles are close to emergence: http://go.osu.edu/GrowingDegrees.
We might be lucky this summer. Last year’s drought should have reduced populations by affecting the eggs and first instar larvae. That is, unless you kept the lawn moist during the drought.
Scouting for the first adult beetles is simply the best way to control Japanese beetles. Remember, they are only active for a couple of weeks. They can do a lot of damage in this limited amount of time, though, if you do not control these scouts. And traps are a waste of time and money. You are simply attracting more beetles to your yard and do more harm than good.
Know the life cycle for Japanese Beetles: http://go.osu.edu/JapaneseBeetle.
Eric Barrett, OSU Extension Educator, Agriculture & Natural Resources, Mahoning County.