The effect of a UV-deficient environment on the attraction and dispersal behavior of whiteflies, Bemisia argentifolii (Bellows & Perring), and on the transmission efficiency of the whitefly-borne tomato yellow leaf curl geminivirus, was tested under field conditions and through controlled experiments. We found that the rate of tomato yellow leaf curl virus-disease spread to tomato plants grown under walk-in tunnels covered with regular greenhouse plastic sheets increases sharply with time, whereas the virus infection-rate under UV-absorbing sheets proceeds at a very slow pace. Average number of whiteflies trapped under regular plastic sheet tunnels was significantly higher than numbers trapped in UV-absorbing plastic sheet tunnels. Similarly, the average number of whiteflies trapped on yellow-sticky traps placed on the outside walls of tunnels covered with regular plastic was higher than the number trapped on the outside walls of tunnels covered with UV-absorbing plastic sheets. No differences were found in the whitefly’s ability to transmit tomato yellow leaf curl virus under the two types of plastic covers. Whitefly dispersal pattern under the two types of plastic covers was examined using a release-recapture experiment. In each type of walk-in tunnel we established a grid of yellow-sticky traps forming two concentric circles: an inner and an external. Under UV-absorbing tunnels, significantly higher numbers of whiteflies were captured on the internal circle of traps than the external circle. The fraction of whiteflies that were captured on the external circle was much higher under regular covers, when compared with UV-absorbing covers, suggesting that filtration of UV light hindered the ability of whiteflies to disperse inside these plastic tunnels. Our results indicate that the mechanisms by which UV-deficiency protects covered crops from insect infestation and spread of viruses are that the lack of UV interferes with insect flight orientation; and that the lack of UV radiation alters the normal behavior of the invading insects, resulting in reduced dispersal activity.
tomato yellow leaf curl virus