|Liu, T.-X. - TAES A&M UNIV.,WESLACO,TX|
Submitted to: Entomological Science (Japan)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2007
Publication Date: August 1, 2008
Citation: Greenberg, S.M., Jones, W.A., Liu, T. 2008. Bemisia tabaci (Homoptera: Aleyrodidae) instar effects on rate of parasitism by Eretmocerus mundus and Encarsia pergandiella (Hymenoptera: Aphelinidae). Entomological Science. 11:97-103. Interpretive Summary: The sweetpotato whitefly, Bemisia tabaci (Gennadius), Biotype B, ranks among the most noxious insects attacking agronomic and ornamental crops around the world. The sweetpotato whitefly cause damage directly through its feeding and by excretion of honeydew, and indirectly by plant virus transmission. The development of integrated pest management programs, including the use of natural enemies, should be the main strategy of crop protection against whiteflies. Encarsia pergandiella Howard (indigenous) and Eretmocerus mundus Mercet (exotic) are two of the most promising parasitoid species in the south central United States. The long term goal of the presented research is directed at improving our knowledge of the interrelations between these two species, and the predictive impact on biological control of pests like sweetpotato whitefly. Our studies defined host instar preference for both parasitoid species. These findings provide additional important information toward explaining elements of interspecific interaction, and combined with ongoing research, should lead toward more efficient use of parasitoids to manage whiteflies. The information is also useful in improving parasitoid rearing efficiency.
Technical Abstract: Studies were conducted to compare preference among Bemisia tabaci Gennadius, Biotype B instars for parasitization by Encarsia pergandiella Howard and Eretmocerus mundus Mercet when provided one instar only, two different instars, and four different instars simultaneously. In the single instar-choice treatment, E. mundus was more successful in parasitizing the younger host instars, while E. pergandiella parasitized a greater proportion of the older instars. Similar results were observed when parasitoids were provided a choice of two instars in six different pair combinations. When all four instars were provided simultaneously, the highest percent parasitization by E. pergandiella was in third instars (17.2%); and the lowest in first instars (2.8%). The number of first, second, and third, instars parasitized by E. mundus was not significantly different between each other (range 10.3-16.4%), but all were signifcantly higher than parasitism in fourth instar nymphs (2.1%). This information furthers our understanding of the mechanism involved in parasitoid competition.