Corynespora ‘Target Leaf Spot' in Alabama Cotton: Fungicide Effect and Variety Response

The pathogen Corynespora cassiicola causes target-like necrotic lesions on cotton, Gossypium hirsutum, leaves – it is commonly known as target leaf spot and can also cause complete defoliation of the plant. A study was conducted during the 2013 growing season to determine the effect of fungicide treatment and variety in target leaf spot management. An irrigated field study was initiated in May of 2013. Field study inputs were supported by a grant from the Alabama Cotton Commission. Treatments were arranged in 2x7 factorial experimental design with main plots being the fungicide treatments (with or without) and the sub-plot treatments being the variety (7 varieties). Treatments were replicated 4 times. The appearance and severity of the leaf spot was rated on the Florida 1-10 scale every 2 weeks beginning after first bloom. Cotton variety maturity was tracked, for the fungicide treated plots, weekly after first bloom by counting nodes above white flower. Final results will reflect fungicide effectiveness, variety susceptibility or resistance, and maturity effect on the occurrence of this leaf disease.