Battle of the Beetles

Once again Japanese beetles are back and munching on our favorite plants. 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.

temp-post-image
Adult Japanese Beetle

Japanese beetles tend to skeletonize leaves, leaving the midribs. It’s important to remember that the beetle damage is just cosmetic on woody plants. By July, they have stored enough reserves to make it through to the next spring. Japanese beetle feeding damage will not kill the plant.

temp-post-image
Japanese Beetle damage

Combatting Japanese Beetles

By Hand

Whenever possible we prefer using a non-chemical approach at The Growing Place. The simplest and most sustainable method is to knock them into a bucket or tub of soapy water. Japanese beetles tend to be a bit sluggish in the early morning hours and will drop straight down when knocked off your plants. A daily round of hitting them into a bucket can control small populations. The beetles emit a scent that attracts more beetles so by catching them early and often, you can reduce their numbers significantly.

Using Traps

There are Japanese beetle traps available. They work using pheromones, so the traps will attract a lot of beetles from a wide area. You will most likely attract your beetles plus the ones feeding in your neighbors’ yards.

Preventative Measures
• Let your lawn go dormant—Adult beetles prefer to lay their eggs in lush, well-watered sunny lawns so letting your lawn go dormant makes it less attractive to the adult beetles. Your grass may be a little brown but you won’t have as many grubs waiting to emerge next year.

• Plant trees—Adult beetles lay few eggs under tree canopies.

• Provide habitat plants—encourage beneficial tiphiid wasps that kill adult beetles and grubs by planting forsythia, peonies and tulip trees.

Chemical Measures
**NOTE: Chemical approaches are broad spectrum. They are toxic to bees and all types of insects including beneficial insects. We mention these methods so you know what products are available but we encourage you to use chemicals only as a last resort.**

The grubs feed on the roots of turf grass and are vulnerable to a number of chemical applications. Apply grub control lawn treatment with active ingredient imidacloprid only once in mid-July to reduce next season infestation.

temp-post-image
Grub/Larval stage

According to Dr. Phil Nixon at the U of I Extention, "Adult Japanese beetles are difficult to control. Carbaryl (Sevin), bifenthrin (Talstar), cyfluthrin (Tempo), lambda-cyhalothrin (Scimitar), or permethrin (Astro) foliar sprays provides protection for about two weeks." You should also avoid using these on host plants like linden or roses that bloom during the Japanese beetle flight season to avoid impacts to pollinating insects. 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.

NOTES AND WARNINGS:

• Broad spectrum insecticides will kill all insects when applied, including beneficial insects and bees.

• We have noticed that birds are feeding on the beetles more than ever, so you may want to hold off applying strong insecticides, such as Sevin. Plus, some products are toxic to mammals and fish. Always read and follow the label directions thoroughly before applying.

• Do NOT apply foliage sprays when the temperatures are above 85 degrees as you may burn or scorch your plants.

For some good myth-busting on Japanese beetles, check out this article from the U of I Extension.

Source: 2017 JAPANESE BEETLE UPDATE BY DR. PHIL NIXON

Aurora Location

2000 Montgomery Road,

Aurora, IL 60504

Phone. 630-820-8088

Naperville Location

25w471 Plank Road,

Naperville, IL 60563

Phone. 630-355-4000

Fall Hours

Monday-Friday: 9:00am-6:00pm
Saturday: 9:00am-5:00pm
Sunday: 11:00am-5:00pm 

 

Growing for the future with
right plants in right places.