Hand-picking, sprays help control Japanese beetles
By Alma Gaul
QUAD-CITY TIMES
Japanese beetles have emerged in the Quad-City region, settling in for a four- to six-week feeding frenzy on some of our favorite flowers, trees and fruits.
Japanese beetles first were identified in the United States during 1916 in New Jersey and have been slowly making their way westward. Illinois is considered totally infested, while western Iowa has yet to experience the shiny metallic-green bug with the coppery wings.
The beetles defoliate many kinds of plants, “skeletonizing” the leaves by eating all but the veins. This doesn’t kill the plant, but it looks bad, and if the plant is defoliated year after year, it could weaken and go into decline. The beetles especially like roses, raspberry bushes and linden trees, but they’ll eat more than 300 different types of plants.
Here are some common questions about Japanese beetles (JBs, for short) and answers:
Q: What can I do about JBs?
A: Iowa State University Extension, Ames, recommends vigilant hand-picking in the morning and evening. Scout your yard every day and get out early and late when the beetles aren’t very active and either squash them or tap them into a bucket of soapy water to drown them. They die quicker in water with soap, making it better than plain water, ISU entomologist Mark Shour says.
This is 100 percent effective and environmentally safe, and the earlier you get on top of the situation, the better off you’ll be because the beetles seem to be attracted to damaged plants and to others of their kind.
If you have a large yard and a lot of plants, this obviously can be a big job.
Keeping your roses clipped during times of peak JB activity also seems to help because the beetles are drawn by the flower’s floral scent. Of course, the flower is the very reason gardeners grow roses, so this can be tough love.
Q: Isn’t there some kind of spray I can use?
A: Yes, but most of these are poisons that kill beneficial bugs as well and introduce more chemicals into our environment.
The most common product is Sevin, with the active ingredient carbaryl. Carbaryl is a nerve poison; beetles pick it up by eating plants that have been sprayed or by being sprayed with it themselves. Carbaryl washes off with rain and breaks down in sunlight, so it needs to be reapplied.
“During heavy adult activity periods, you may need to spray every 10 days,” says Andy Kay of The Green Thumbers in Davenport.
ISU/Scott County Extension horticulturist Duane Gissel cautions you to be careful when you spray so you don’t kill bees that pollinate plants. Either don’t spray plants in bloom or spray early in the evening when pollinators have left for the day.
Another product with a higher relative toxicity is Suspend SC, with the active ingredient deltamethrin, which is a stomach poison, says Alec Schorg of Aunt Rhodie’s in the Village of East Davenport. It is mixed with water and sprayed on plants and can be expected to last up to three weeks, which is longer than Sevin, he says.
A nontoxic product called Surround at Home also may help. This product is 95 percent kaoline clay, a naturally occurring mineral that is mixed with water and sprayed on the leaves of plants, coating them with a milky, mildew-looking film. The film masks the plants so the bugs don’t come to eat or, if they do, they turn away because eating coated leaves is like eating chalk, Schorg says.
At present, this product is not generally sold in retail stores, but it is available online at gardensalive.com.
There is also a systemic insecticide called Merit that can be used on trees, shrubs and perennials to protect the plants from the inside out; it is found in Bayer Tree and Shrub Insect Control and Bayer All in One Rose and Flower Care, according to Wallace’s Garden Center in Bettendorf.
Whatever you use, always read and follow all label directions and precautions before using any pesticide, including “natural” or “organic” controls, Gissel says.
Q: Beetles come from grubs, so can I control Japanese beetles by using grub control on my lawn?
A: Lawn grubs are the immature stage of many kinds of beetles that eat grass roots, killing the turf above. If you have had a lawn grub problem, then you may want to treat for them.
Common preventative products are Merit and Marathon, containing imidacloprid, which is a growth-inhibitor, or Mach 2 and GrubEX, both containing halofenozid. These are applied early in the season before grubs have a chance to get big.
But just because you have killed grubs doesn’t mean you won’t have beetles. They can simply fly in from elsewhere.
Q: What about traps?
A: The general consensus is that traps will attract and kill a lot of beetles — bucketfuls, in fact — but they may draw beetles to your yard that otherwise would go somewhere else.
They are sometimes used as a way to draw beetles away from prized plants in an area that is already highly infested, but ISU entomologists do not recommend them otherwise.
Alma Gaul can be contacted at (563) 383-2324 or agaul@qctimes.com.