Knowledgebase

Japanese beetles #862498

Asked March 25, 2024, 6:40 PM EDT

Hi! I don't have anything left in my yard that Japanese beetles like, but they are breeding under my lawn. Do you know is a way to treat this problem in the spring?

Denver County Colorado

Expert Response

Hello,

Yes, you can apply an insecticide that provides season-long grub control. The active ingredient is called acelepryn and it's sold as Scotts GrubEx (it's the only product that contains that active ingredient). It's extremely safe, pollinator-friendly, and if applied at the right time of year, controls all white grubs through the fall.

Apply it in early June (not before) and water it in with at least 1" of water (or time with precipitation). The product takes awhile to move to the roots of the turf where the grubs feed. 

Apply with a push-type fertilizer spreader set to the correct setting - you will be surprised of how little product it looks like you're applying, but more is not better.

Although you've de-beetled your yard, your neighbors probably have plants that are desirable to the beetles, so you might still get some grubs that find your lawn. Another option is to try to keep the lawn on the drier side during their flight and mating season (July-August) since the eggs need moisture to survive. 
Alison O'Connor, PhD Replied March 25, 2024, 7:29 PM EDT
Thank you, Alison!  I did try to research this, but couldn't find a very good solution.  This is perfect.  And I think those darn beetles are expanding their palate, or maybe I'm imagining it.

Also, my husband and I spent an afternoon at the Spur and had a tour.  It was so interesting and well done.

I really appreciate your prompt response!

Lisa

On Mon, Mar 25, 2024, 5:29 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied March 25, 2024, 8:48 PM EDT
Thank you, Lisa! I'm so glad you enjoyed the Spur Campus - there is so much to see and do. Good luck with the beetle battle this summer.

--Alison
Alison O'Connor, PhD Replied March 26, 2024, 12:18 PM EDT

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