Good morning, please read below for a current update on row crop diseases from our disease specialist, Dr. Robert Kemerait:
Southern corn rust was found yesterday in Terrell, Houston, and Bleckley Counties – it looked like it had been there a little while. The picture below is of an infected stalk from Terrell County. The County Agent says that field is at “black layer” so there is no need to apply any more fungicide. The question will be not grain fill, but how well those stalks will hold up until harvest.
Keep an eye out for this disease as it is moving closer and closer to Macon County. If you think you may have southern corn rust or have questions about this disease, please give me a call.
The next picture below is of foliar and vascular symptoms of Fusarium wilt on cotton out of Turner County. Note the faded foliage and discolored vascular tissue. These are dead giveaways. The county agent in Turner County is also pulling nematode samples as Fusarium wilt here in GA goes hand in hand with nematodes.
The next picture below is of eye spot on corn in Screven County. This can look superficially like rust at quick glance. It is caused by the fungus Kabatiella zea. “Eye spot” is rarely a yield-limiting problem, but can look ugly. It is most common in the corn belt (we are in the corn show-lace) but is most problematic during cooler and wetter growing conditions. Fungicides can be effective, but are they profitable for this disease?
Asian soybean rust continues to be found, primarily in kudzu, but in some beans, across the Coastal Plain. Should bean growers apply a fungicide at full bloom in South Georgia? Yes, I would.
The two pictures below are Stemphylium leaf spot. Yellowing-reddening on this cotton is sure-sign of potassium deficiency getting started. Spots are Stemphylium leaf spot as a result. Fungicides won’t help. If you believe you may have this problem in your field, getting potassium out to the crop will help.
Cotton- Note the reddening and wilting in the picture below. This could be and often is Cotton leafroll dwarf virus. But may not always be. These early symptoms most common in DG 3615, but seen in others as well.
Peanuts- I haven’t seen to much leaf spot or white mold yet, but the conditions are perfect now. Kind of like a cigarette smoldering in the cushions on a couch when you go to bed at night. It could ignite any time. Do not try to play the “catch up game”. It’s very hard to win that game. Stay on a good program to prevent!
As always, if you have any questions about identifying a problem in your field or which fungicides to spray, please give me a call or contact your local County Agent.