I had a call this morning from a customer wanting to know what all the beetles were on her roses. “There are about 10 per blossom. They are eating the flowers and have eaten a lot of leaves already. They weren’t there the last time I looked! What do I do?”

The Peoria area is becoming infested with Japanese Beetles, an insect that wasn’t around 3 or 4 years ago. It has been around other parts of the country for years. We knew it was coming, but nothing could be done to stop it. Now it is here to stay and is likely to increase in population over the next few years.

The beetle is a 3/8 to 1/2 inch, greenish-bronze metallic color with white spots on its hind end. Japanese Beetles will be here into early August but are peaking now. It starts as a white grub in the lawn; don't confuse it with the grub of the June Beetle. There are now two white grubs to deal with. Fortunately, they can both be controlled with Merit, and NOW is the time to apply it. So it will be effective when the eggs hatch and the grubs start feeding.

Controlling the Beetles

You are thinking, “But what do I do NOW to keep the Japanese Beetles from feeding on my plants?” You can always knock them off the plant into a bucket of soapy water. That’s the safest control and the one that raises the fewest concerns about effectiveness or ecological impact.

If it isn’t the best option for you, the sprays you can use are:

• Sevin (Carbaryl)
• Permethrin
• Ortho Systemic Insect Killer (Orthene, or acephate)
• Ortho Rose and Flower Insect Killer (bifenthrin insecticide)
• Ortho Max Garden and Landscape Insectic Killer (esfenvalerate)
• Bayer Rose and Flower Insect Killer (cyfuthrin and imidacloprid)

Multiple applications are needed. The beetles are great flyers and will come in from other places. They live for about 6 weeks. Insecticides with Merit or imidacloprid provide very good control as a soil drench. But this takes awhile to be taken up into the plant. It needs to be used before you see the beetles.

Japanese Beetle Traps

There are differences of opinions on the use of the Japanese Beetle traps; some scholars feel that they may end up drawing more beetles to your garden than they will actually catch. Although we have heard reports of horticulturists who used them last year and had good success with them.

These beetles feed on a lot of different plants (over 400!). They really like roses, Linden trees, and crabapple trees. While they won’t do long term damage to the plants, they do make it look bad. You can find a lot of information on the web about these pests. For the most reliable information, stick to the ones published by professionals, such as the universities, arboretums, or nurseries.

Best of luck in keeping them controlled.

--Dave