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Corn, Small Grain, & Watermelon Updates

Dr. Bob:

Corn

Stunting pattern in a corn field, Colquitt Co GA, 2022. – Jeremy Kichler

“The symptoms of stunting and the pattern in the [corn] field above could be associated with several different things. In my world, this absolutely could be the result of a problem with plant parasitic nematodes. In Dr. Glen Harris’s world of soils and soil fertility, it could be something else. Most importantly, this image helps us to better identity what it might be, what it might not be, and where best to go into the field and hunt for answers.

Southern corn rust, south FL 2022.

In the picture [above] you see field corn that is ‘covered up’ with southern corn rust in south Florida, the disease of greatest concern to corn growers in Georgia. Unchecked, southern corn rust can take 80-90 bu/A.  At current prices, that is a pile of money lost.

Southern rust WILL impact Georgia’s corn production in 2022. The question is not ‘IF’. The question is ‘WHEN’. ‘When’ depends on how quickly rust spores, living rust spores, move from south Florida and the Caribbean to Georgia.  They require upper wind currents to move long distances, but UV light easily kills them.” 

Rome Ethredge:

Oats

Rust disease on oats, south GA 2022. – Rome Ethredge

“We are seeing some rust disease in oats now and it can be serious. Here are Dr. Alfredo Martinez’s comments, ‘Crown/leaf rust, caused by the fungal pathogen Puccinia coronata f. sp. avenae, is one of the most problematic and damaging diseases of oats in Georgia. Yield losses associated with crown/leaf rust range from slight/moderate to full crop failure.’ We really don’t want the rust to get on the flag leaf. There are many fungicides labeled for oats. [We] will include Oat Disease controls in the upcoming 2023 Ga Pest control Handbook.

Wheat

Wheat flag leaf drying, south GA 2022.

I’ve had several comments…concerning wheat for grain where the leaves and even flag leaves are drying or dyeing. Several things or likely a combination can be causing this, the most common being dry, windy weather. This seems to be occurring most in sandy areas of the field that would be most susceptible to drying out. I’ve also seen it in too wet areas of the field where the roots aren’t doing well.  

Other possibilities are: running out of nitrogen, and sidedressing was early on and if it’s a sandy field that has had a lot of rainfall since then. Fusarium foot rot is possible especially if the field has often been planted to wheat.

Also could be Barley Yellow Dwarf disease but usually there’s some reddish color with that.”

Watermelon

Fusarium wilt (right) in watermelon, Crisp Co GA 2022. – Josh Grant

Been looking at a lot of watermelons the past two weeks and have seen maturities between just transplanted to vines/runners up to 6′ long. Regardless of plant size, still on the lookout for Fusarium wilt symptomology. Some fumigated with chloropicrin while bedding, some have set grafted plants, and many used Proline up front.

The two main chemical control options post transplant once wilt pops up are Proline (5.7 fl oz/ A rate) and Miravis Prime (11.4 fl oz/A rate). Up to three applications of proline at that rate are labeled per season (1 soil and 2 foliar) at 5- to 10-day intervals. Miravis Prime can be applied twice at that rate (foliar or direct nozzle or chemigation) per season with 14- to 21-day interval. For more details, see labels below.

Miravis Prime, Cucurbit Vegetables Label
Proline 480 SC, Cucurbit Vegetables Label