Every year during the month of June, we see the emergence of Japanese beetles and the damage that they inflict on our gardens and landscape.
During the past week, I have witnessed damage on peach trees, Canna lilies, crape myrtles, and a little in my garden. They can be found by looking for the actual beetles which are generally less that one half inch long, and have a metallic green body with copper-brown wing covers.
The other scouting method is witnessing their damage, that is generally characterized by eating the plant materials between the veins and leaving the skeleton of the leaf behind. In large numbers, these beetles can cause a great deal of damage to your plants.
The best control of these pests come when you have a combined approach that targets both the adult beetles and the larva. Adult beetles usually 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. If you catch them early and don’t have too many, hand picking is an effective control.
Simply pick or shake off the beetles and drop them in a buckle of soapy water. This is easiest to do in the early morning when the beetles are less active. For larger infestations, spray with Sevin.
Be sure to read and follow all label directions. During heavy activity, you will need to spray every 3-5 days. Because Sevin is deadly to bees, please spray when bees are less active, generally during the hottest part of the day from noon to around 5 pm. When using Sevin on vegetables for insect control, there is a wait period of 3-5 days before they are safe to harvest and eat. 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 ordinarily be there.
While we easily see the adult beetles and the damage they do, the larval form can cause extensive damage as well. This 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.
Heavy infestations can destroy large areas of turf to the extent that the grass can be rolled up like a carpet. You can dig a sample (3 inches deep) to determine their presence.
Control measures are warranted if you have more than 10 grubs per square foot. 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 diazinon, trichlorfon, imidacloprid (Bayer Advanced), cyfluthrin (Bayer Advanced Lawn and Garden), 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 popillae.
Spores build up in the soil over 2-4 years as grubs ingest them and die. Japidemic and Doom are milky spore products. When using any insecticide or other product, it is essential that you read and follow the product instructions on correct usage.
We are always here to help at the Banks County Extension office. Ways to contact us are to call us at 706-677-6230, by email at email@example.com, or to come by the office at 413 Evans street, Homer.