I now talk of my garden in relation to a new season — Japanese beetle season. Let the trumpets sound. It’s time to scout for Japanese beetles. Evidence suggests that adult beetles are attracted to previously damaged leaves. Reducing feeding damage now can result in less feeding damage in the future.
Japanese beetle adults are one quarter to one half inch long with copper colored wing covers and a shiny metallic green head. Kind of attractive in a buggy sort of way.
Japanese beetles also have the munchies for your favorite rose, linden, grape, raspberry and some 350 different plants. They generally do not feed on dogwood, forsythia, holly, lilac, evergreens and hosta. Plants in the smartweed family such as Persicaria are good indicators for Japanese beetles since they usually find those first.
Japanese beetle adults feed on flowers and fruits and skeletonize leaves by eating all the leaf tissue and leaving the veins. Adults are most active from 9 a.m. – 3 p.m. on warm, clear summer days. Feeding is normally in the upper portions of plants. Beetles prefer plants in direct sun, so heavily wooded areas are rarely attacked.
Adults are present until mid-August. After mating, females lay eggs in turf which hatch into grubs in August. Grubs feed on plant roots until cold weather drives them deeper into the soil. Adults emerge in summer of the following year.
The bacterial control, milky spore, sold as Doom or Grub Attack is commonly recommended to control Japanese beetle grubs. However, it only controls Japanese beetle grubs and not our predominate lawn grub, annual white grub. Common lawn grub controls such as Acelypren, imidocloprid (Merit) and beneficial nematodes will control several species of beetle grubs. Call Metzger Landscaping at 260-982-4282 to sign up for a greenkeeper lawn care program to control grubs and weeds in your lawn with a Greenkeeper Fertilizer & Lawn Care Program.
The beetles are good fliers and easily fly a couple miles in a single flight. They may travel 10 to 15 miles from where they lived as larvae. Typically, one-third of the adult Japanese beetles fly to a new host each day.
Generally pesticide sprays of cabaryl (Sevin) to control the adults can reduce damage for up to two weeks. However, Sevin is toxic to bees and other beneficial insects. Synthetic pyrethroids can also be effective to control Japanese beetles. Informally the repellent Neem has not been shown to be effective.
Picking Japanese beetles off by hand every morning may be just as effective as spraying. When disturbed, the beetles fold their legs and drop to the ground. Hold a can containing rubbing alcohol or soapy water below the infested leaves. Move the plant and the beetles will drop into the container and be killed. This is best done in the morning when they fly slower.
Japanese beetle traps are not recommended where a large beetle population exists. It has been shown repeatedly that the use of these traps results in increased plant damage compared to not using the traps.
A number of birds such as grackles, cardinals and meadowlarks feed on adult beetles. Two native predator insects and a couple of introduced parasites may help to keep Japanese beetle populations in check. Protect natural enemies by keeping the use of conventional pesticides to a minimum.
Several methods of control include floating row covers over the fruits, Pyola sprays (combination of canola oil and pyrethrum), and hand collecting.
Although damage looks devastating, Japanese beetle feeding rarely kills woody plants. Therefore, confine control of beetles to plants in important landscape locations or plants of value.
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