Effects of host plant on whitefly biology and behavior.

Abstract

The whitefly Bemisia tabaci (Genn.) is an important vector of plant viruses in many parts of the world. Knowledge of whitefly biology and behavior is essential to understanding whitefly-virus epidemiology. Oviposition rates and offspring survival on a variety of healthy and virus-infected plants were compared (cotton with cotton leaf crumple virus, pumpkin with watermelon curly mottle virus (WCMoV), zucchini with WCMoV, cantaloupe with lettuce infectious yellows virus (LIYV), lettuce with LIYV, and tomato with chino del tomate virus). The proportion of offspring surviving to adulthood varied among the six healthy crop species. Ranking of percent immature survival was as follows: zucchini > cantaloupe > cotton > pumpkin > lettuce > tomato. There was no correlation between oviposition rate and the rate of immature survival of B. tabaci. It appears that virus infection of plant host can have a significant effect on oviposition and survival rates of whiteflies. Pumpkin plants infected with WCMoV showed the most severe disease symptoms of all virus-host combinations, and also showed a significant increase in the proportion of offspring surviving on the virus-infected host versus the non-infected host. LIYV-infection showed no direct impact on oviposition or survival rates in either lettuce or cantaloupe, while virus-infection in other combinations (with the exception of pumpkin) showed detrimental effects on offspring survival. Greenhouse studies comparing movement of whiteflies from LIYV-infected pumpkin to lettuce and cantaloupe plants indicated that whiteflies were initially attracted to lettuce plants (likely due to color), but subsequently accumulated in cantaloupe. Although total offspring production in this study was lower on lettuce plants, a portion of the whitefly population fed and oviposited on this host of relatively lower suitability, even when a host of higher suitability was accessible. Populations of whiteflies taken from different host sources behaved differently in dispersal studies. When whiteflies were taken from a cotton source, the proportion of whiteflies leaving a cotton plant in 24 hours was significantly lower than the proportion leaving a cantaloupe or lettuce plant. When taken from a pumpkin source, the proportion leaving a pumpkin plant was significantly lower than the proportion leaving a cotton or lettuce plant. This suggests that dispersal time is related to the host source of the whiteflies and not to host suitability. Differences in behavior due to host source may have a serious effect on virus epidemiology and should be considered when conducting any behavioral studies.