Most new southern varieties are Rust resistant.
Now we have that out of the way – what is in your field?
Compare the wheat you planted against the UGA 2014 wheat chart. This resource will help you in determining what could be in your wheat.
Rust. Please check using a white cloth to see if you can rub off any spores. The colors to look for are red/brown, yellow, orange, or any combination. (See LSU chart below.) Wait two days after a rain to do this as rain will wash off the spores. Rust is very aggressive when the temperatures are right and must be controlled quickly. Do not allow many days to pass before you check your fields. Call me if you find Rust on a AGS variety.
Powdery Mildew and BYD (Barley Yellow Dwarf). Look for white to gray powdery fungal growth on leaves and leaf sheaths. Tip yellowing, purple leaves, and/or twisting of leaves are symptoms of BYD, which is a virus, and fungicides will not control it. You must put something out to control aphids before you get the virus. See LSU info on BYD below.
Cold/Frost Damage. You could just have cold/frost damaged wheat. The conditions have been right cold-frost damage, and some early planted field have it. Yellowing, streaking, tip burn, and purple tips are caused by frost/cold damage.
Manganese Deficiency. Manganese is another problem in fields with HIGH Ph. The photo is of a confirmed manganese deficient field.
I generally find the flag leaf to be the one of the things I want to protect, along with the wheat head. Leaf Blotch, Fusarium, and Glume Blotch must be controlled to have good wheat yields. Fungicides do not trans-locate well and need to be on the surface they are to protect. Please wait as long as possible or if you must spray early then plan to spray twice.
Tissue test your flag leaf. Do not get the largest tiller in each plant, as it will get the first choice of N and give you a skewed reading. I prefer to ample from one of the smaller tillers because that is where your yield will be increased. These smaller /later tillers will dry-up if you do not have proper fertilization.
*Information obtained from 2015 Georgia Pest Control Handbook (http//www.caes.uga.edu/publications) , Intensive Wheat Management in Georgia, and LSU. As always, follow label and dispose of empties properly.