Dealing with white grubs in lawn - Ask Extension
From your article (https://extension.umn.edu/yard-and-garden-insects/japanese-beetles), it looks like we have Japanese beetle grubs in our lawn. Rakin...
Knowledgebase
Dealing with white grubs in lawn #788796
Asked May 01, 2022, 5:55 PM EDT
From your article (https://extension.umn.edu/yard-and-garden-insects/japanese-beetles), it looks like we have Japanese beetle grubs in our lawn. Raking the dead patch turns up live grubs in the top 1" of soil. We'd like to seed the dead/bare patch; do you have guidance on treating? At this time (a cool May 1), is a product like GrubEx (Chlorantraniliprole) effective treating infested ground, or should we wait for warmer weather and use a curative treatment? Would GrubEx applied in Spring offer protection to parts of the lawn that are not obviously dead? We have grass seed and topsoil -- should we hold off until we've treated the area? Or can we apply a treatment after the soil is roughed and raked and seeded? Finally, is there a preferred method for handling the dead grass layer (with some grubs in it, surely); are there risks putting in compost pile or yard waste collection? Gosh -- that's a lot of questions. Thank you for your insights! -glenn
Hennepin County Minnesota
Expert Response
Treating the grubs in May won’t do much because the grubs have already done the damage to the spring lawn. Overseeding can be done now and treatment for grubs done in July.
From the article,
“Do not treat in spring because the large grubs are hard to kill, they feed for a relatively brief time and rarely cause damage in the spring. Treating in spring is no guarantee that the lawn will not be re-infested again in mid-summer.”
So GrubX won’t do much in the spring.
The dead grass can be left on the ground or raked up and composted. Or the dead grass can be placed in a bag and put in direct sun for a couple of days the heat will kill the grubs.
The article is fairly dense but comprehensive and worth reading over a couple of times.
From the article,
“Do not treat in spring because the large grubs are hard to kill, they feed for a relatively brief time and rarely cause damage in the spring. Treating in spring is no guarantee that the lawn will not be re-infested again in mid-summer.”
So GrubX won’t do much in the spring.
The dead grass can be left on the ground or raked up and composted. Or the dead grass can be placed in a bag and put in direct sun for a couple of days the heat will kill the grubs.
The article is fairly dense but comprehensive and worth reading over a couple of times.
You're right -- a lot of stuff in the article. I'm having a hard time determining how much of my sad lawn is "do over" and if there are parts not eaten that can be treated as preventative with the GrubEx (figuring there are at least some grubs in those areas).
Do you think it's worth putting GrubEx down in early summer in the next ring out from my most damaged areas? Or treat the whole lawn as if it's in a curative phase?
Again, thank you so much for your time in fielding my questions. -g
From: askextension=<personal data hidden> <askextension=<personal data hidden>> on behalf of Ask Extension <<personal data hidden>>
Sent: Sunday, May 1, 2022 6:42 PM
To: Glenn Krocheski-Meyer <<personal data hidden>>
Subject: Re: Dealing with white grubs in lawn (#0058727)
Sent: Sunday, May 1, 2022 6:42 PM
To: Glenn Krocheski-Meyer <<personal data hidden>>
Subject: Re: Dealing with white grubs in lawn (#0058727)
The entire lawn should be treated in early summer. Treating before there are large numbers of grubs is the most effective strategy. Grub populations also tend to be cyclical, a year with a lot of damage followed by a year with very little, more the year after that and then another year with lots.
