A MULTIVIRUS EPIDEMIC OF TOMATOES IN ALABAMA

During 1992, a multivirus epidemic reduced tomato production by as muc h as 25% in the major tomato-growing region of Alabama. Estimated yiel d losses of 100% resulted from the epidemic in over 250 ha in two coun ties of North Alabama. Cucumber mosaic cucumovirus (CMV), alone or in combination with potato potyvirus Y (PVY) and/or tobacco etch potyviru s (TEV), was responsible for the crop failure. CMV was detected alone or in combination with PVY and/or TEV in over 70% of the samples teste d and was present in 90% of the fields surveyed. In 1993, 21 tomato fi elds were monitored weekly from transplanting through harvest for CMV, PVY, TEV,tobacco mosaic tobamovirus, and tomato spotted wilt tospovir us. All 5 viruses were detected, with CMV occurring most frequently. I ncidence of CMV at the 61% level or higher was found in 16 of the 21 f ields surveyed. Tomatoes transplanted in April and May were least effe cted and had relatively low virus incidence until late in their develo pment. Tomatoes transplanted in June and Jury were infected at an earl ier age, had the highest virus incidence, were the most severely affec ted, and suffered the greatest loss in yield. In 1994, Aphis gossypii, the cotton aphid, was the most common virus vector found during an ap hid monitoring/virus spread study. Populations of A. gossypii peaked i n late June, immediately preceding a period of rapid CMV incidence and spread.