WNPR

Connecticut Garden Journal: Taming the Japanese Beetle

Jul 30, 2015

This iridescent, copper-colored beetle hails from Japan, has been around since 1916, and is not a picky eater. Japanese beetles feast on grapes, cherries, raspberries, cannas, basil, roses, and lots of other plants. They often feed en masse, devastating plants. 

There are many organic controls for Japanese beetles. While the soils are too cool in New England for milky spore disease powder to work well, beneficial nematodes will kill grubs in the soil when sprayed in June and August.

Neem oil spray can deter their feeding. Japanese beetle pheromone traps will also work to a limited degree. But this year, I'm trying two new organic sprays.  

Kaolin clay consists of fine clay particles that are sprayed on plants. It creates a white film on the leaves that Japanese beetles hate, so they're less likely to feed and will go elsewhere for a meal. It washes off in rain, so it will have to be reapplied.

Japanese Beetle activity peaks from late June until early September.
Credit Holly / Creative Commons

If the kaolin clay thwarts them, where they probably will go is on my roses and cannas. The downside of kaolin clay spray is it discolors the flowers and leaves.

That's not very appealing. That's why I was excited to find a new form of Bt, Bacillus thurigiensis galleriae, called BeetleJUS.

It kills Japanese beetle grubs and adults. It works like other forms of Bt. The beetle eats the bacteria on the leaves and dies soon after.It's safe for beneficials, pets, wildlife and kids. So hopefully, BeetleJUS to the rescue for my roses.