Treat Grubs this late in fall? (Maryland)

I’ve read conflicting things about whether you should apply Grub control products in Fall. It’s likely insecticide companies trying to sell more insecticide. I’m sure the spring is a better time to prevent grubs. But, that’s not my situation.

It’s Mid-October you’ve invested a lot in a fall overseeding/watering… the cost of failure is high. You just found a Grub… Do you treat it or wait till spring?

Questions:

1. How long will grubs continue to eat my roots?
2. Are the chemicals in Grub Ex going to have a long term negative effect on my soil?
3. Besides the wasted $15 to cover my lawn, any reason to not
   do it.

ADDITIONAL BACKGROUND:

I’m near Baltimore, MD. Tall Fescue.

Did an overseeding… have spent a small fortune on water the past month (have had no rain)… was carefully hand raking an area of my lawn where no grass seed was growing to give it one last try for the year and found a Grub. Honestly, I feel like i’ve used a lot of water… and the idea of putting more seed down in the spring potentially and having to repeat daily waterings again makes me sad.

So, I’d rather burn $15 now then use a lot of water in the spring to fill these spots.