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Timing of GrubGone application #870097

Asked May 25, 2024, 7:39 PM EDT

Hello.  I am looking for updated information about when to apply GrubGone to my lawn to help control my Japanese beetle infestation.  I had new sod laid in my yard a few years ago which had a lot of Japanese beetle larvae, and them made the mistake of planting grape vines.  Either the vines go or I have to have some way to manage the beetles beyond picking them off.  There are literally thousands.  I just spend $87 for ten pounds of GrubGone.  I need to know what is the current recommendation for when to apply it.  Your turf recommendations say May (which makes sense because there are lots of grubs in my lawn).  However, the Japanese Beetle fact sheet from 2018 says mid-summer.  Do you have more recent information?  

Denver County Colorado

Expert Response

Using GrubGone for other insects does start in May. But the recommendations specifically for Japanese Beetles are mid-summer: July and August.  This is when female beetles are laying their eggs, which hatch immediately and the small grubs start eating grass roots.  If you kill the grubs at this stage, they won't emerge the next year.  

To kill beetles this year as they emerge as adults, you need to use chemical controls or pick the adults off your grapes by hand. 

If you want the latest on Japanese beetle information, Whitney Crenshaw, retired professor at CSU, is still doing research on Japanese beetles.  Here is more than probably want to know:


https://webdoc.agsci.colostate.edu/bspm/ProGreenExpo2018/JBEA.pdf
Colorado Master Gardener, Denver County Replied May 28, 2024, 4:00 PM EDT
That answers my question!  Thank you.

On Tue, May 28, 2024, 14:01 Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied May 29, 2024, 10:43 AM EDT

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