If it is I live in Florida, and I am up in Gainesville and the temperatures now are staying around the low 90s to high 80s every day. That is still normal growing conditions for Bermuda.

So if it is not dieases related it could be bug related. We recently had an out break of Fall Army worms on our practice green. Those can cause a good amount of damage and cause the Bermuda to look like it has gone dormant.

A simple way to check this would be to do a soap flush of your lawn. Simply get a 1 gallon jug, or what ever you can find close to that, and add one to two tablespoons of Dawn or some hand dishwasher detergent, and mix that up. Spread that over your lawn on about a 1x1 or 2x2 area. Allow that to soak in for about 20-30 seconds, and then look very closely for very small worms, or any other bugs. Army worms look brown, and are very small. About 1 cm long. Have to look very close. If you see them I would apply some broad spectrum insecticide, and maybe a selective insecticide for Army worms.

Reason being is clear. Gasoline will burn your grass, and herbicides could damage your turf. I have seen it to often on golf courses were a worker will spray roundup on weeds in the rough and then walk out onto the fairway and you can see his foot prints all over it.

Other than that it would be hard for me to understand exactly why this is happening at the tire marks. Your also using a walk mower, and those wont leave heavy wheel tracks so compaction shouldn't be an issue.

How ever, Bermuda is known to thatch even common Bermuda. So I would consider possibly airifcation next spring. That might help.

As for the stalks, I am assuming you are talking about the Stolons? Or stems located closer to ground level. Yes in Bermuda those tend to take on a woody like appearance especially if it is allowed to get tall. That should not be a problem as long as your not seeing spots of brown on the stolons, stems, or leaves. That could be disease.

As for mowing height there will be a lot of recommendations for Bermuda. There are a bunch of cultivars available now. The trick is to determine what type you had.

If you seeded your lawn it is most likely Common Bermuda, or Princes. Prince however is marketed as a ultra dwarf, and should be mowed at green heights (I am assuming you didnt use this type ). So if it is common I would still mow it at 2" and not let it get higher than 3".

If you know it is a different cultivar then let me know. My first guess would be Tifway 419 as that is the most common sodded Bermuda. That can be mowed down to 1/2 and sometimes lower. I would still only mow that at 2" the highest and 1" the lowest for home lawns.

Hope that helps, and look forward to hearing back from you.