Plant some dill and the beneficial insects will clean up the beetles.
I let the dill go to seed so it comes back every year, and I haven't had a
problem with Japanese beetles for years.

Frank

What are these "beneficial insects"?

Frank, do you grow roses as well?

Beneficial insects include ladybugs,praying mantis,parasitic wasps,lacewings.
Almost every kind of beneficial insect I looked up was attracted to dill. I read
an article in American Nurseryman probably ten years ago on beneficial insects and almost everyone listed was attracted to dill.
Thats when I started growing dill.

Frank

Japanese beetles don't really have predators. I recommend going out once day when they get bad and dunk the beetles in a bucket of soapy water. It works about as well as insecticides and doesn't hurt anything except the beetles. You can also try using Milky Spore on your lawn but I've been told it doesn't work as well in the colder zones. The beetles do love apple trees and I have issues every year with them, but the trees survive even with a lot of damage to their leaves.

Japanese beetles have a lot of predators.

Frank

Here is a link that might be useful: Link

One year I had a wheel bug living in the fronds of the aparagus. I watched it kill Japanese Beetles.

Plant four 0'clocks; the beetles love them . . .they are poisonous

Plant four 0'clocks; the beetles love them . . .they are poisonous

stupid beetles.

Frank- do you have to collect the seed & replant, or does the dill self-seed readily? I'm in Z5, also, and have dill for the butterflies, but most DEF will plant more of it on your recommendation.

Yes, dill will self seed. Some times I collect the seed and spread it around to other parts of my five acres. The praying mantis population has exploded since I started planting dill. The babies are coming out now.

Frank

I call B.S. on that article. I've got birds in the hundreds here and they don't bother Japanese beetles enough to help. I highly doubt insects would help much either since these are flying monsters that can come from your neighbors' yards as well (who may not do anything to control them in their yard). Planting dill is also not going to eliminate these monsters. I grow dill and the Japanese beetles still come each year. I used milky spores last year too, but the neighbors didn't. Bummer.

There are less of them this year because several people used the beetle traps and caught and killed thousands of them. If you live in a big neighborhood, there is no way to make all the neighbors help with the problem.

I normally drown in soapy water, but I'm not home much lately, so that's not going to work. I read somewhere to cover plants with shade cloth - which would definitely work. May try that on my rugosa roses (that's all they really seem to bother in my yard outside of an occasional trip to the hydrangeas as an appetizer). OTOH, looking at plants covered in shade cloth isn't very attractive during high summer...

*!^@%!$@!!! BEASTS!

Beneficial nematodes will kill the larvae. I've applied the nematodes for years, and we don't have many Japanese beetles here now. But that could be partly due to our flock of free-ranging guineas as well.

If you use beetle traps you will only draw in more beetles. If you use a lot of chemicals you will kill the beneficials. I was a grower for a nursery that would spray first and ask question later. In my own nursery business I do very little spraying and get nothing but compliments from the state inspector.

Frank

Fruit tree growers and gardeners (like me) have been using horticultural kaolin clay sprays to protect their plants and fruit from pests. The brand name is Surround. It's mixed with water and applied with a sprayer.

I strongly recommend it to protect your plants against chewing beetles, caterpillars, sawflies, and other pests.

I wouldn't spray it on blooms, but it can be used on fruits, veggies, and foliage.