Question
I live in Georgia and in our front yard, we have circles of dead grass. My stepdad calls them 'dollar signs' although I have never heard that terminology before. A neighbor of ours thinks it is caused by grub worms. How can I tell if it's grub worms causing the problem or something else?  

Answer
Hi Tiffany;
Your neighbr thinks it is grubs. I am more inclined to think it is brown ptch fungus.
did up a shovelfull, thurn it over and see how many grubs you see. If you see more than 8, that may be the problem.
Garb a handful of it and see how hard it is to pull up. If it pulls up easily, REAL easy, and not many or no roots come up with it, and especially is it seems a little damp and slick on the ground where you pull it up, probably brown patch, but some kind of fungus, for sure.
Treat it with baking soda disolved in water.
Disolve some baking soda in water, probably about 1/4th cup per gallon, in your garden sprayer, and spray the area well, or drench the area of the spots.
For grubs, well, I no longer have grubs, since I have been on a totally organic program.
For every harmful insect you have in your yard, there are hundreds of beneficial ones, that the insectisides also kill.
If you are not on an organic program, but hve not put any chemicals on your lawn for a few months, (2 to 4 would be enough even) it is a good time for you to go organic.
Beneficial insects and lawn critters ( toads, lizards, grass snakes, etc) will keep all the harmful insects eaten and out of your yard, better than all the insecticides put together, and they work cheap.
All they need for pay, is a healthy enviornment, chemical free, for them to live in.
Treat with the baking soda if that is brown patch, or even doesn't seem like brown patch, if there are not a ton ( 8 or more) grubs in that shovelful of dirt, treat with the baking soda. It won't hurt it, and if it is some other kind of fungus, it will fix it.
Then apply sugar ( plain table sugar) 1 pound per250 sq.ft, and water it in well. ( I would apply the sugar and water well, then after the water soaks in well, spray or drench with the baking soda where the circles are..
The sugar will nourish the beneficial microbes that enrich your lawn.
When there is no danger from chemicals, critters will start moving in and feeding off the harmful insects.
Now if Aliens are making crop circles in your yard, I can't help you. LOl
Wish they would land in MY yard. I would love to meet aliens. LOl
Charlotte