LABORATORY AND FIELD-EVALUATION OF EXOTIC PARASITOIDS OF BEMISIA-TABACI (GENNADIUS) (BIOTYPE-B) (HOMOPTERA, ALEYRODIDAE) IN THE LOWER RIO-GRANDE VALLEY OF TEXAS

We evaluated a total of 38 exotic and 2 native parasitoid populations of the sweetpotato whitefly Bemisia tabaci (Gennadius) (Biotype ''B'') (Homoptera: Aleyrodidae) (= silverleaf whitefly, Bemisia argentifolii Bellows and Perring), using laboratory and held experiments. Numbers of B. tabaci parasitized were counted in sleeve cages on cantaloupe me lons (Cucumis melo L. cv ''Perlita''), cotton (Gossypium hirsutum L. c v ''Delta Pine 51''), and broccoli (Brassica oleracea L. cv ''Patriot' '). Highest attack rates were found for Encarsia nr. pergandiella (Hym enoptera: Aphelinidae) (Brazil) and Eretmocerus mundus Mercet (Spain) on melons; Eretmocerus sp. (Pakistan) on cotton; and Eretmocerus mundu s (Spain) on broccoli. In the laboratory, these three exotic parasitoi ds attacked significantly greater numbers of hosts than the native spe cies of Encarsia pergandiella Howard and Eretmocerus tejanus Rose and Zolnerowich. Selected exotic parasitoids were evaluated in the field u sing sleeve cages on melons, cotton, and kale (Brassica oleracea L. cv ''Siberian kale''). Eretmocerus spp. from Spain and India performed w ell, in all crop types. Encarsia nr. pergandiella (Brazil) performed w ell on melons, but not on kale or cotton. Selected exotic parasitoids were released at various sites throughout Hidalgo County in the Lower Rio Grande Valley of Texas. Of 29 populations released in the held, el even were later recovered. Two Eretmocerus species (Spain and Pakistan ) were commonly recovered throughout the evaluation period. This infor mation will be used to prioritize the parasitoid cultures for mass rea ring and release in biocontrol-based IPM programs against B. tabaci.