Dr. Bob K:

“The Big 3 foliar diseases of cotton: target spot, areolate mildew, and bacterial blight, have been found.  While ‘the sky is not falling’, the best management of areolate mildew and target spot is with judicious and timely fungicide applications. I believe yield of cotton can be affected by target spot until the 6th week of bloom, until with in 4 weeks of defoliation for areolate mildew.  When defoliation from either disease reaches 25%, or so, I think chances of slowing them with a fungicide is small.  What’s at risk? Up to a half bale of lint.

Target Spot

Target Spot in Cotton – Jeremy Kichler, Colquitt Co, GA, 2021
Target Spot in Cotton – Josh Grant, Crisp Co, GA 2021

Growers most likely to see benefit from applying fungicide for target spot have a crop with 1) high yield potential, 2) excellent growth, 3) disease appears at or soon after first bloom, and 4) grower makes fungicide application by 3rd week of bloom.


Growers least likely to see a benefit from a fungicide application are those who a) have poor growth and a crop suffering from nutrient deficient, b) apply fungicide where target spot never develops, c) apply fungicide after target spot has cause 25% or more defoliation.


Best fungicides for managing target spot are Priaxor and Miravis Top. Both are very tight in supply. Headline is also very good and also tight. Quadris is fair to good, but may be the only option.

Bacterial Blight

Bacterial Blight in Cotton – Josh Grant, Crisp Co, GA, 2021
Bacterial Blight in Cotton – Cale Cloud, Grady Co, GA, 2021
Bacterial Blight in Cotton – Josh Grant, Crisp Co, GA, 2021

Note the blocky, geometric shapes of these spots that are delimited by the leaf veins.  Note also the symptom (“lightning bolt” appearance) when the disease goes systemic. The only control is to plant resistant varieties. Bacterial blight of cotton will lead to pre-mature defoliation, and, more importantly, a distinctive boll rot. Here’s to hoping the blight won’t get too severe in these and other fields.  The weather is absolutely perfect for spread and these is nothing we can spray to stop it.”

Areolate Mildew

Areolate Mildew in Cotton – Jeremy Kichler, Colquitt Co, GA, 2021
Areolate Mildew in Cotton – Jeremy Kichler, Colquitt Co, GA, 2021
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