from Bob Kemerait UGA Plant Disease Specialist
Recent wet weather, high humidity, and excellent growth of the cotton crop are really bringing this fungal disease on now. Here are some important points to share with your growers:
1. Look for initial spots deep in the interior of the canopy. Note the numerous target-like lesions.
2. 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.
3. 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.
4) in Georgia growers should consider spraying fungicides to manage target spot from the 1st week of bloom until the 6th week.
5) Growers who have had losses to target spot in the past may want to spray preventatively. Most growers will spray after disease is identified early in the epidemic.
6) losses to target spot of cotton in Georgia are often between 150-250 lb lint/acre
7) 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.
