Dr. Fred Bourland

Professor|University of Arkansas

2024 Abstract - FRUSTRATIONS EXPERIENCED WITH VERTICILLIUM WILT IN COTTON: Verticillium wilt is fungal-induced disease of cotton, which can limit production by progressively plugging the vascular system (“plumbing”) of the plant. Symptoms of the disease include wilted leaves, vascular discoloration and pre-mature boll opening. The disease is most commonly found on silt loam soils, but some exotic germplasm lines have expressed symptoms on the Sharkey clay soil at Keiser. This finding suggests that the pathogen may be widely spread on different soil types, that most varieties express some resistance, and that the disease may sometimes be associated with yield plateaus. Counter to common production practices in our area, incidence of the disease can be lessened by increasing plant rates (plant densities), reducing nitrogen, limiting irrigation, and lowering boll load! The Arkansas Cotton Variety Test at Judd Hill (near Trumann) provides an opportunity to evaluate varieties under relatively heavy Verticillium wilt pressure, and annually produces variation in leaf symptoms among varieties. Attempts to visually rate disease symptoms as a measure of disease resistance has been frustrating and often confounded by variation in crop maturity. Variation in ratings of leaf symptoms may be associated with variation in resistance, maturity and/or boll load. Relative yield over multiple years is used as an indicator of tolerance to the disease, but this measure has limited use in a selection program.