Influence of Squash vein yellowing virus on the biology and behavior of its whitefly vector

Plant viruses can modify the performance and behavior of insect vectors. The aim of this study was to learn more about the host plant mediated modification of whitefly settling and oviposition behavior caused by the semi-persistently transmitted SqVYV, one of the most detrimental plant viruses infecting watermelon. The objectives of this study were to compare settling and oviposition preference of whiteflies on mock-inoculated and infected squash and watermelon, and on watermelon at 5-6 and 10-13 days post inoculation (dpi). For these experiments, whitefly settlement was recorded up to 72 h and eggs were counted after 72 h. In the first experiment, whiteflies initially showed no preference for mock-inoculated or infected watermelon, but after 8 h, whiteflies preferred mock-inoculated plants. They also laid more eggs on mock-inoculated watermelon. However, there were no distinct settlement and oviposition preferences on squash. In the second experiment, by 24 h, whiteflies preferred to settle on mock-inoculated instead of infected watermelon at 10-13 dpi. There was no preference, however, if the plants were 5-6 dpi. More eggs were laid on mock-inoculated than infected watermelon at 10-13 dpi but no difference was found at 5-6 dpi. The initial equal preference of whiteflies increases the chance of whiteflies becoming viruliferous, and the shifting of whitefly preference to mock-inoculated plants increases probability of virus spread. SqVYV symptoms are more severe in watermelon than in squash. This may explain the shift in settling preference in watermelon but not squash. Our results help explain the rapid spread of SqVYV in watermelon.