GARDENING: Where have the Japanese beetles gone?

My colleague in Van Wert County, Dr. Curtis Young, mentioned the same thing. Another colleague, during a conference call we have each Tuesday regarding horticulture happenings around the state, Dr. Dave Shetlar (aka BugDoc) said, “Typically when this happens, you can bet that the adults have mated and found a suitable egg-laying location and then died.”

After they mated and laid eggs, they died. End of story. Or is it?

What this means is that Japanese beetles in our area that were present early on and are not present now have probably laid their eggs in lawns. We MIGHT have a good Japanese beetle grub population soon.

So, what should we do? Nothing – just wait it out and scout for them. Except for if you had Japanese beetle damage in your lawn last year. If you had a grub problem last year you may want to be on the lookout for grub damage soon.

My daughter lives in Northridge (Clark County) and several lawns in this area had symptoms of grub damage in late August and early September 2023. Most reseeded their dead spots in the fall.

Some treated lawns earlier this spring (during a good window for preventative), but not all. We are in sort of the middle of a period for best control.

Japanese beetle adults lay their eggs in nice green, healthy, moist turfgrass areas. Since we are in a moderate drought, they may not have laid eggs in somewhat dormant lawns. On the other hand, if you irrigate your lawn and keep it nice and green, you have the perfect environment for egg-laying.

Egg survival is most successful in a lawn that receives frequent shallow watering. So, dormant turfgrass currently is not a bad thing.

There are biological and chemical control options, each with its benefits and risks. There are curative chemicals (applied in late August or early September), preventive (applied from June to early August, almost too late), and another preventive that is applied in May or June.

If you are going to use a lawn company, talk with them to find out what is being used and what is most effective currently. In addition, if you are going to do it yourself, determine the timing and the product. Your local Extension office Agriculture and Natural Resources Educator or Master Gardener Volunteers can help with this.

As I mentioned, we are at an in-between time for the best applications of chemicals so determine first if you have Japanese beetle grubs and then what to use to control them.