Question

yellow  
grass   QUESTION: Hi Ron

I live in Chicago. I noticed a hole about 3" in diameter in my back yard. Over the past week, I noticed the grass above and around it started to turn yellow and is easily coming off (see original hole down and to the right of where I peeled it). I have not seen any snakes or rabbits or any other critters around. This screams Grubs, but with the coincidence that it's happening right around that hole, I wanted to get an expert opinion.

If it is grubs, is it too late to put Grub-Ex (or something similar) down? Can I patch the grass with some lawn repair? What steps do I take to make it normal again?

Thanks!
ED

ANSWER:  "....and is easily coming off...".   In extreme infestations, one can roll up the turf like a carpet! The turf shows signs of drought stress and separates at root level. This does indicate the possibility of grubs. Their presence is easily confirmed by digging down and examining the excavated soil. A post-hole shovel is best; but I carry a bulb planting tool and a soil sampling probe for this purpose.
On the other hand, it could be a fungus infestation. In such cases the turf usually shows signs of water-logging; the grass sloughs off (separates) at the "crown" which is above ground. There is a brown to black discoloration of sheaths and internodes and, in extreme cases there is an objectionable odor.
Regrettably, I cannot offer an opinion about any vertebrate pests.    

---------- FOLLOW-UP ----------

QUESTION: Thanks

In your first paragraph you say "The turf shows signs of drought stress" and in your second paragraph you say "In such cases the turf usually shows signs of water-logging". As you can see, the rest of my lawn is in great shape so it's neither overly watered or drought stricken. Must be grubs. Just by the photos, would you draw the same conclusion? And if it is grubs, would putting Grub-Ex down now kill them and prevent them from doing further damage?

Answer
From the images, I'd say that the discolored turf looks more drought stressed than over watered. What puzzles me is the "hole" and what caused it. That alone might account for the discolored turf. In that case, filling the hole and sodding the area is all that is required.
I cannot recommend the application of a chemical unless the presence of "target" is established; and a threshold of infestation is reached.