When is the best time to treat for grubs?


The warmer weather earlier in the Spring the last few years has shifted the treatment for grubs in landscapes to earlier and earlier. Do you know when the best time or date in the Spring is now for this year? 


Jonathan Foster, Home Horticulture Outreach Professional

Let me refer you to our UMaine Cooperative Extension fact page on White Grubs, put together by our Integrated Pest Management team. As you’ll see the recommended treatment is chlorantraniliprole and the treatment window is about 3 weeks before the expected emergence of the grubs to begin feeding (if you can already see grubs, it’s too late to treat for that generation, giving the treatment lead time to incorporate into the soil is crucial), which they place in mid-April for Maine.

However, I reached out to our Extension entomologist, Charlie Armstrong, for further guidance in case the warming springs do affect the treatment recommendations. His reply:

“I would say you can’t be too early with chlorantraniliprole because it has a really long half life in the soil (up to 1130 days, in fact)!  So the only limiting factor with it would be whether or not the ground is still frozen or covered with snow.  So long as the ground can absorb it, and you can get it watered-in afterwards, then you can afford to be early with it.  And far better to be early than late, actually.  It will still be effective all season long, so nobody should be worried about using it too early.”

So if your soil is warm enough to be actually absorb the treatment, it’s ok to do it and you won’t lose anything by being earlier than the 3 week window before they starting eating the roots of your lawn.

Happy gardening.