As if it wasn’t already difficult to grow roses in Oklahoma, we are now battling Japanese beetles too. Normally, I don’t like to include words of war in my posts, but battling Japanese beetles is just that. War.
Identifying Japanese beetles
From the University of Illinois Extension: “Adult Japanese beetles are stocky and range from about 3/8 to 1/2 inch long. They are metallic green with coppery wing covers. There is a row of white spots along each side of the abdomen just below the wing covers, as well as two white spots on the back end of the abdomen.”
These beetles are a menace
I never saw these green and brown beetles in my garden until last year, and I’m hearing from all of you that they are a menace in your gardens too this year. Populations rise and fall based on food sources. Oklahoma received a lot of great rain in May, and while our gardens are plentiful, the insects, good and bad, are too.
Japanese beetle larvae
Japanese beetle larvae are white grubs, but we have a lot of insects in our gardens that start out as white grubs. I squish all the white grubs I see in the soil. I know it’s gross, but wear gloves. Or, if you have chickens, they’d love to eat this little grub.
What do Japanese beetles eat?
Japanese beetles love eating roses. From what I’m hearing from my garden coaching clients, the beetles also seem to be eating a lot of Hibiscus syriacus, rose of Sharon. I cut my rose of Sharon shrubs back late so they aren’t blooming yet. I’m not seeing them on my perennial hibiscus, but the grasshoppers are eating those.
Japanese beetles eat over 300 species of plants from root to flower. The larvae eat the roots, and the adults consume everything else.
What are Japanese beetles’ natural predators?
In their native Japan, Japanese beetles have more natural predators than they do in the U.S., but Tachnid flies seem to eat more Japanese beetle adults than some of our other predators.
Battling Japanese beetles
Pesticides are not very effective unless you use a broad-spectrum pesticide, but you know what that means. You will also kill pollinators and other insects. Broad spectrum means nearly everybody. I’ve heard some people use a systemic pesticide, but that’s also off limits in my garden.
So how do I battle Japanese beetles? I use a Yeti cup with a handle and soapy water. I’ve turned my hunting into a game. Each morning and at lunchtime, I walk outside with my bright pink Yeti cup and flip those beetles into the water. They sink into the soapy suds, and I flash the victory sign.
You must work fast though because they are very good flyers.
I know this sounds like a wimpy battle plan, but it actually works if you start early. From the University of Minnesota Extension, “[b]eetle-damaged leaves emit air-borne chemicals that attract more beetles. By physically removing them, you’ll reduce the number of new beetles attracted to your plants.”
More info please
If you’d like to learn more about this very irritating insect pest, please check out this Rosechat podcast episode where Teresa Byington interviewed Dr. Raymond Cloyd from Kansas State University, an expert on rose diseases and pests. He’ll tell you the same thing I have. Soapy water and handpicking reduces their numbers until next year.
Now, get out those Yeti cups and get to work.