It’s that time again – Japanese beetles have arrived. Beginning as grubs, then pupae and now emerging from our lawns as Japanese beetles, this invasive pest is characterized by its coppery metallic wing case, black legs and little white spots. It has been around since at least 1916 and it feeds on more than 300 kinds of plants. You will typically find the beetles on roses, grapes, hibiscus, lindens, cherries and birches. Japanese beetles tend to skeletonize leaves, leaving the mid-ribs. How do you combat this pest?
Perhaps the easiest and most sustainable method is to knock them into a bucket or tub of soapy water to drown. Japanese beetles tend to be a bit sluggish in the early morning hours. They also will drop straight down when knocked off your plants. A daily round of hitting them into a bucket can control small populations. Beetles emit a scent that attracts more beetles so by catching them early and often, you can reduce their numbers significantly.
Japanese beetle traps are available. They are a pheromone trap, so they will attract a large amount of beetles from a wide area. You may attract your beetles plus the ones feeding at your neighbors.
Adult beetles prefer to lay their eggs in lush, well-watered sunny lawns. With this year’s considerable rains, we all have lush lawns. Usually in July rainfall is scarcer, so consider allowing your lawn to go dormant. The larval stage of the beetle feeds on the roots of turf grass and is vulnerable to a number of chemical applications. To treat the larvae, apply a grub treatment to your lawn in late July to August, following package directions.
Pesticides may be used to kill adult beetles, however you need to make sure the product touches the insects. Neem oil or pyrethrins are organic broad spectrum options. There are also systemic insecticides that are applied via soil drench, but it is too late to apply them now. Systemics need to be in place six weeks in advance of the infestation. Check out the University of Illinois Extension Service’s excellent website and blog with treatment recommendations.
Posted on 7/9/2013 at 8:15:00 PM