POPULATION-LEVELS AND PARASITISM OF BEMISIA-TABACI (GENNADIUS) (HOMOPTERA, ALEYRODIDAE) ON PEANUT CULTIVARS

Sweetpotato whitefly, Bemisia tabaci (Gennadius), has recently become a pest of peanut in the southern United States. Limited observations i n grower fields had identified differences in infestation among cultiv ars. We wished to determine whether selected cultivars grown commercia lly in this region resisted whitefly infestation and whether parasitis m by aphelinid parasitoids differed among cultivars. Five cultivars we re evaluated in summer 1992 and six in summer 1993. In 1992, 'Florunne r' supported the greatest populations of red-eye nymphs and 'Southern Runner' supported the lowest populations. Encarsia nigricephala Dozier was the most common parasitoid (53.0% of all parasitoids reared), fol lowed by Encarsia transvena (Timberlake) (25.6%), and Encarsia pergand iella Howard (18.3%). Parasitism was uniformly high and species compos ition on the five cultivars did not differ. In 1993, 'Southern Runner' supported the greatest populations of all immature whitefly stages ex cept red-eye nymphs. 'Marc I' supported the lowest levels of whitefly infestation. E. nigricephala was extremely abundant in 1993 (85.3% of all parasitoids reared), followed by E. pergandiella (9.8%), and E. tr ansvena (4.7%). Eretmocerus nr. californicus was found in low numbers in both years. Again, in 1993, parasitism was high on all cultivars (u p to 100% by the end of September), and no differences were noted in t he parasitoid composition among the six cultivars. Whitefly infestatio n was light in these noninsecticide-treated peanut plots, most likely because of natural control by native aphelinid parasitoids, and other beneficial insects.