Clients have been asking me about Japanese Beetles lately. These creatures can be a minor nuisance or a major problem. But don’t panic and grab the pesticide.
First, know that these pests will only be around for about a month. Second, they don’t tend to damage all plants. And, third, most plants will survive an attack.
Some of the most susceptible types of plants are: Maples (especially Japanese Maples), Rose of Sharon, Roses, Hollyhocks, Grapes, Cherries, Plums and Peaches. Some Crape Myrtles are also susceptible. Plants under stress will usually be more attractive to the beetles. So keep your plants healthy and watered during droughty conditions.
Monitor susceptible plants for the insects or for damage. Japanese Beetles skeletonize leaves by feeding on leaf tissue between veins. NC State University has a good information sheet on Japanese Beetles. The sheet’s description of possible controls include both mechanical and chemical tactics:
Homeowners can take advantage of the beetles’ aggregation behavior by shaking plants to dislodge beetles each morning. Without beetles already on a plant, it is less likely that beetles will aggregate there later in the day. Picking beetles off by hand will also reduce the accumulation of beetles that results in severe damage. They can be easily knocked into a widemouth jar of soapy water. In some settings, flowers or plants can be protected with cheesecloth or other fine mesh.
If insecticides are desired to protect plants in the landscape, there are a number of products available. For home use, carbaryl (Sevin), malathion, imidacloprid (Merit) are good choices. Many of the newer lawn and garden multi-insect products containing one of the pyrethrins are also effective. Pyrethrin containing chemicals are slightly more persistant. Sevin will protect foliage for about five days, weather permitting, so it would have to be reapplied. Pyrethroid based products may give up to two weeks of foliar protection per application. Spinosad and Neem based products are less effective, but are preferred by some gardeners seeking “softer” chemicals. Homemade concoctions and blended beetle cocktail repellants are slightly effective at best, and may need reapplication every one or two days.
Use beetle traps if you really like them as garden ornaments. Here’s the thing: traps attract beetles, so keep them far away from your plants. Better yet, give a few as gifts to your neighbors to put in their yards.
Try paying children to collect beetles from your plants. They’ll have fun dropping them into jars and you’ll be out a few bucks. Of course you may not want to tell the kids you’ll kill the beetles afterwards.
So, don’t panic, take a look at your plants and decide on your best tactic. You may find you don’t have to do anything at all.