Verticillium Wilt On-Farm Applied Management Options 2014

Verticillium Wilt is caused by Verticillium dahliae, which colonizes the vascular cylinder of the plant and causes defoliation, stunting, and yield loss. Eighteen cotton varieties were planted and evaluated for resistance to Verticillium dahliae. The trial was planted on the Tate farm in North Alabama. Plots were six rows each, and approximately 500 feet long. The field was irrigated, when needed, with a drip tape irrigation system. Disease ratings were taken September 20. Ten feet sections of the third row in each plot were observed for total number of plants and stems were cut longitudinally to assess disease incidence. Disease severity ratings of foliar symptoms were evaluated on a scale from 1-5 with 1 having no foliar wilting, 3 having interveinal chlorosis and necrosis of the leaves and 5 having completely defoliated plants. Four replications of each variety were counted. Petioles were taken from infected plants of each variety and re-isolated to confirm the presence of Verticillium dahliae.  In regards to disease severity, the top varieties displaying the least amount of foliar symptoms and the most resistant varieties were ST 4946 GLB2 and FM 1944 GLB2. None of these varieties received averaged scores exceeding 2. In terms of disease incidence, ST 4946 GLB2 had the lowest number of plants with darkened vascular systems. PHY 339 WRF, ST 4747 GLB2 and ST 5032 GLB2 all displayed vascular staining and average percent of disease incidence ranged from 50.25-53%. These percentages were statistically similar and performed better than the resistant check FM 1944 GLB2.