Late Summer/Early Fall Japanese Beetle Management

 

Internet Photo from Jim Baker, North Carolina State University, Bugwood.org

Killing adult Japanese beetles all summer is time consuming and monotonous.

Thank goodness the adults are dying off as we head into the fall months.

What about their egg laying offspring? Where did they go and what are they doing all fall, winter and next spring?

Easy answer. If adult beetles were in your garden chewing your plants this past summer, then females have laid eggs in your turf grass or turf grass next door, up and down the street and pretty much everywhere grass is growing. 

Then their eggs grow quickly from the egg stage to larvae or white grubs, their longest stage in their one-year lifecycle. 

Although larvae are out of sight under the grass, they are spending the next nine to ten months living, growing and dining on turf and plant roots. They slow down eating when it's super cold, but rarely do they die from cold temperatures, snow and drought conditions. They are very tough little buggers.

Larvae will live in the turf soil all winter and emerge as adults next June or July. 

It's wise to use a grub killing product on the lawn now before the soil turns cold when larvae will move deeper down into the soil.  

The chart showing all the chemicals and organic products that work on Japanese beetle grubs can be found HERE. 

Please use care when applying lawn chemicals and all products since they can do harm to pollinators and other beneficial insects. Read ALL the fine print on the bag to learn more about application dos and don'ts.

My personal favorite completely organic (not harmful to other insects) grub control product is called grubHALT!™ and can be purchased locally in independent Colorado garden centers and online.

The protein that kills larvae in grubHALT!™ needs to be 50 degrees or warmer to be active for the larvae to eat and be effective. It is okay to apply after aerating the lawn. Just be sure to water the product in right away. Wait several days after applying grubHALT!™ to fertilize the lawn for the final time of the season.

Fall applications to kill the larvae are recommended because as winter progresses and soils get colder, the larvae move deeper into the soil under the lawn. So hit them now when they are closer to the surface. 

Next summer adult Japanese beetles will likely return to your plants, they fly in despite that fact that you treated your lawn this fall, it's just the way it is. You'll still be glad you killed this season's brood.

Japanese beetle Resources: 

Japanese beetle Management in Colorado

Hope for Japanese Beetle Control in Colorado 

JB Plant Feeding Lists - from no to heavy feeding  

Report JB Feeding in your Landscape

Japanese Beetle Fact Sheet from Dr. Whitney Cranshaw