I have been noticing Japanese Beetles on several different types of plants for the past two weeks. Most gardeners know this enemy well. The damage adult beetles do in a short period of time can destroy flowers, plants, and vegetables.
Feeding on the upper surface of leaves, they eat the tissue between the veins, leaving a skeletonized appearance to the damaged leaves.
Japanese beetles are metallic green with copper-brown wing covers. Beetles emerge from the ground in June and feed on more than 300 different plants. They live 30-45 days. During that time females lay 40-60 eggs in the soil. The grubs hatch after 8-14 days and spend 10 months underground feeding on plant roots and organic matter. Their one-year life cycle comes full circle as adults emerge next June.
Adult beetles feed in masses and tend to prefer plants in direct sun. Their presence attracts more beetles as they emit pheromones (odors) that attract other beetles to feed and mate.
Hand picking beetles in the early morning is an effective control. Simply pick or shake off beetles in a bucket of soap water. For larger infestations, you can use carbaryl (Sevin). Be sure to read and follow all label directions.
Because carbaryl (Sevin) is deadly to bees, please spray when bees are less active. Do not spray during the hottest part of the day, from 10 a.m. to around 5 p.m. Pheromone traps are not recommended for use in the landscape. They do trap beetles, but in doing so they attract many more beetles to your yard and garden than would normally be there.
The Japanese beetle grub is a white grub that is C-shaped when disturbed. White grubs feed primarily on roots of turf grasses, but they also attack roots of ornamental trees and shrubs.
The most effective time to control the grubs is during the early spring or late summer when they are close to the surface of the ground. Applying trichlorfon, imidacloprid (Bayer Advanced), dinotefuran, or halofenozide (Grub-B-Gon) to the soil in areas where grubs are active will control them in that specific area.
For organic controls, treat the ground with Bacillus thuringiensis (Bt) or milky spores. Bt is a naturally occurring soil bacterium typically used as a microbial insecticide. Bt products include Dipel, Biotrol, and Thuricide. Milky spore is the common name for the spores of Bacillus papillae. Spores build up in the soil over 2-4 years as grubs ingest them and die. Doom is a milky spore product name.
The good news about Japanese beetles is that they can be effectively managed with minimal damage to your landscape.
If you have any questions regarding beetles or other gardening topics, you are welcome to contact the extension office at 770-749-2142 or email firstname.lastname@example.org.
For more information and details on upcoming events, check out the Polk County Extension office on Facebook by searching “UGA Extension Polk County.”