Management of Sweet Potato Leaf Curl Virus in Sweetpotatoes Using Insecticides1,2

ABSTRACT Sweet potato leaf curl virus (SPLCV), which is transmitted by the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), species complex, can severely affect yields of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae). This virus is endemic in sweetpotato fields at the U.S. Vegetable Laboratory (USVL), Charleston, S.C. In 2010 and 2011, experiments were conducted to determine if repeated insecticide applications were useful for protecting ‘Beauregard’ sweetpotato from SPLCV infection. In 2010, plots were untreated or treated twice weekly with imidacloprid. A row of SPLCV-infected sweetpotato genotype ‘W-258’ was planted between ‘Beauregard’ plots to serve as a source of whiteflies and SPLCV. A similar test was performed in 2011, except that the plots were sprayed only once a week, and a rotation of four insecticides (in the order of imidacloprid, pyriproxyfen, acetamiprid, and pymetrozine) was used. Yellow sticky traps were placed horizontally in the center of each plot at canopy height to monitor whitefly abundance. Leaf samples were taken every other week to test for SPLCV infection using real-time polymerase chain reaction (PCR) techniques. Over the two-year period, there were significantly fewer whiteflies on sticky cards in the sprayed treatment for only two of the 36 weekly samples, indicating that insecticides were largely ineffective in reducing whitefly populations moving into these plots. By the end of the growing season each year, all of the unsprayed plots were infected with SPLCV as determined by real-time PCR. However only about one-half of the sprayed plots were infected with SPLCV. This indicates that insecticides could be useful in protecting sweetpotatoes from SPLCV. The insecticide sprays would likely be more effective under normal production practices where sources of the virus are not in such close proximity to the uninfected crop.