I recently thatched my lawn to oversees my lawn and have extensive damage from grubs. The grass just pulls up with dirt attached but no roots present. Many grubs are visible-around 20- in a 12” square. Am I safe to put down seed now and treat for grubs in the spring or do I need to treat for grubs before putting down my seed? Any help is greatly appreciated. Thanks! Sincerely
Harford County Maryland
Turf-type tall fescue is the recommended grass for sunny lawns in Maryland. It doesn't build up a thatch layer like bluegrass which was planted in the past. (Core aeration does a good job of opening up the soil for overseeding.)
It also doesn't tend to have grub problems, however 20 per square foot is a lot, and could warrant treatment. It is too late to treat for this season to get the best results.
We would wait until June or July to count again, and then treat at that time with Grub-Ex.
It is late/tricky to seed now as well. We'd suggest re-seeding in March/April.
Here is our page on Grubs: https://extension.umd.edu/hgic/topics/grubs-lawns