I have 2 feet of dead grass circles in several areas of the yard; they appeared after a hot humid spell.
The Gardener’s Answer
Hi, Jerry: There are a few different possibilities of why there are dead circles in your lawn. First, if you or your neighbors have dogs that use this area as a bathroom this could be the reason. The high acidity of the urine combined with the hot humid weather can cause the grass to burn. This is especially true with female dogs and Kentucky Bluegrass. Diluting the urine as soon as possible will help prevent future problems. Another possibility is grubs,: if you can pull up the grass easily in the areas where it is damaged the culprits will be easily seen if this is the reason. It is perfectly normal to have a few grubs in our lawn but an excessive amount of grubs feeding on the roots of the grass can cause large dead patches. Beneficial nematodes can help reduce grub populations, or insecticides will also help. The third possibility could be a fungal turf disease. For more information on grub control and turf diseases problems, visit the following: www.ca.uky.edu/agc/pubs/id/id112/id112.htm
These are publications available to home gardeners from our Extension Service in collaboration with land grant universities. It is always important to diagnose the problem before treating for it.