Grub control in Lucas County - Ask Extension
I live in Lucas County. What is the time window for applying Merit to control grubs in my area? I would think sometime in June. My lawn care service w...
Knowledgebase
Grub control in Lucas County #900512
Asked May 07, 2025, 4:55 PM EDT
I live in Lucas County. What is the time window for applying Merit to control grubs in my area? I would think sometime in June. My lawn care service wants to apply in now. I think it’s too early. Would it be reasonable to ask them to wait?
Lucas County Ohio
Expert Response
Grubs are a common problem in lawns, but many different species of insects can have lawn-damaging larvae. The Merit label (second link below) states that the active ingredient is imidacloprid. According to the fact sheet from MSU (first link), this is a preventive product that will not kill this year's grubs but when properly applied and managed (ie, timing and irrigation after application) should kill 75-100% of NEXT year's grubs. This sheet has an excellent overview of various products and reasonable expectations of them.
https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn
https://www.domyown.com/msds/Merit_05G_label.pdf
The optimum time to apply this product (Merit) is, as you suspected, after June 1 (actually June 1-July 15) according to the label. That said, there are a couple of other factors to consider. One is that for the product to work, it must be thoroughly irrigated or rained on within 24 hours. Your lawn care service may be trying to time the application with a higher chance of rainfall if you can't easily irrigate after application.
It is also possible that the service has so many lawns to treat that they don't think they can do all of them in the optimal window. Depending on exactly what species of grub is causing the problem, the egg laying period may be earlier or later than usual this year due to climate issues. The goal is to do the application prior to or during the egg laying period of the pest you are trying to manage.
Talk to your lawn service and see if they know what species of grub they are dealing with and if they have a good reason for treating your lawn early. Obviously, May treatment would definitely be before the egg laying period, so it would fit the criteria in that way. I suppose if the pest in question didn't lay eggs until 2 months later the efficacy of the product could be somewhat affected.
Please do be aware that this product is toxic to bees. Flowering weeds should be mowed off before application. Later blooms will still have some of the imicloprid present in their pollen and nectar, but less so. Your lawn service should be aware of this fact and manage accordingly.
Good luck with the grubs, and thank you for asking Extension!
https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn
https://www.domyown.com/msds/Merit_05G_label.pdf
The optimum time to apply this product (Merit) is, as you suspected, after June 1 (actually June 1-July 15) according to the label. That said, there are a couple of other factors to consider. One is that for the product to work, it must be thoroughly irrigated or rained on within 24 hours. Your lawn care service may be trying to time the application with a higher chance of rainfall if you can't easily irrigate after application.
It is also possible that the service has so many lawns to treat that they don't think they can do all of them in the optimal window. Depending on exactly what species of grub is causing the problem, the egg laying period may be earlier or later than usual this year due to climate issues. The goal is to do the application prior to or during the egg laying period of the pest you are trying to manage.
Talk to your lawn service and see if they know what species of grub they are dealing with and if they have a good reason for treating your lawn early. Obviously, May treatment would definitely be before the egg laying period, so it would fit the criteria in that way. I suppose if the pest in question didn't lay eggs until 2 months later the efficacy of the product could be somewhat affected.
Please do be aware that this product is toxic to bees. Flowering weeds should be mowed off before application. Later blooms will still have some of the imicloprid present in their pollen and nectar, but less so. Your lawn service should be aware of this fact and manage accordingly.
Good luck with the grubs, and thank you for asking Extension!
