PIMA AND UPLAND COTTON SUSCEPTIBILITY TO BEMISIA-ARGENTIFOLII UNDER DESERT CONDITIONS

Selected cultivars and breeding lines of Pima cotton, Gossypium barbad ense L., and Upland cotton, Gossypium hirsutum L., were evaluated for susceptibility to Bemisia argentifolii Bellows and Perring under the d esert growing conditions in Imperial Valley, C.A, in 1990 and 1991. Re sults in three of four experiments showed that Pima cottons had higher whitefly populations than Upland cottons studied. Within each cotton species, whitefly populations on the different cultivars and breeding lines were not significantly different. Pima cotton, in general, yield ed less than Upland cotton. Lower lint yields in 1991 than in 1990, fo r the same cottons grown in each year, were associated with higher whi tefly populations. None of the cottons tested showed resistance to B. Argentifolii of economic significance Results emphasize the need to id entify resistance mechanisms and initiate breeding programs to incorpo rate resistance into acceptable agronomic cottons.