Q&A: Japanese Beetles

Tips on what to do if Japanese beetles are taking over your roses.

Q: Japanese beetles are wiping out my roses. I've hung traps, and they're working (they load up quickly), but the roses are still covered with beetles. Am I just attracting more beetles than I had without the traps? Isn't there something that will drive them away?
— Barbara, Atlanta, Ga.

A: Chances are that the traps are attracting more Japanese beetles than would normally be in the area. Traps tend to work better when they're spread over a very large area — when everyone in the neighborhood is using them and also treating the grubs. If you do want to continue using the traps, make sure you hang them far away from the plants you're trying to protect. (Hang them close, and you're only directing Japanese beetles toward your roses.)

Many gardeners just head to the affected plants with a bucket of soapy water in the morning and hand-pick the beetles when they're sluggish. Just combing them off a branch or gently shaking the branch over the bucket works. Hand-picking is especially important early in the season when the adults first emerge. That's because the first adults to appear emit two pheromones — one to signal other Japanese beetles that they've just discovered a great place to dine, and the other, a signal from females that they're interested in mating. No wonder then that getting rid of those early "announcers" can make a big difference in the next few weeks.

Other options: a botanical insecticide — such as one made from canola oil and pyrethrum — works for a direct-contact spray but it's non-discriminant, killing both bad and good bugs.

Treating the soil with milky spore is a good treatment for the grubs but takes a few years to show its effectiveness. It also works better when a whole neighborhood participates.

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