Sweetpotato Tip Rot Disorder Is Enhanced by Pre-Harvest Application of Ethephon and Reduced by Curing

Tip rot is a new sweetpotato disease/disorder in Mississippi with unknown etiology. Since pathogen isolations have been inconsistent, a relationship of this disorder with stress has been suggested. This disorder is manifested as a small sunken and irregular area of ¼” to 1” in diameter at or close to the proximal end of the storage root and appears after several weeks in storage. In many cases necrosis continues internally. To simulate stress, ethephon was applied to Beauregard (B14) prior to harvest in six locations with and without tip rot history. Treated and non-treated as well as cured and non-cured storage roots were stored for 4-8 weeks and evaluated for tip rot incidence. Pre-harvest applications of ethephon increased the phenolic content in the cortex and stele by 57% and 86%, respectively. Tip rot was observed mostly in ethephon treated storage roots and increased with ethephon rate (r=0.78) up to 5.2%. In contrast, curing reduced tip rot incidence to 0.6%. These results suggest that the higher phenolic content as a result of ethephon application enhances the appearance of the tip rot disorder, but curing minimizes this response.