Host suitability of two biotypes of Bemisia tabaci on some common weeds

Significant differences in some reproductive parameters of the B and Q biot ypes of Bemisia tabaci (Gennadius) with regard to four species of winter we eds were determined in a no-choice assay. The highest fecundity (eggs) and fertility (pupae and adults) were obtained with Malva parviflora L. as host , followed by Capsella bursa-pastoris L., Brassica kaber (DC) and Lactuca s erriola L. The percentage of adult emergence (from egg to adult) was signif icantly higher (P < 0.001) with M. parviflora, C. bursa-pastoris and B. kab er than with L. serriola. Except on L. serriola, the mean values of the rep roductive parameters for the Q-biotype were significantly (P < 0.05) greate r than those for the B-biotype. On the other hand, in choice experiments wi th summer weeds, both B- and Q-biotypes preferred Datura stramonium L. and Solanum nigrum L. to Amaranthus retroflexus L., Chenopodium album L. and Ec hinochloa crus-galli L. Significantly more males and females, and more pupa e and empty pupal cases per plant were found on D. stramonium than on S. ni grum. Adult abundance on A. retroflexus, C. album and E. crus-galli plants was very low. At a constant temperature of 26 +/- 1 degrees C, the Q-biotyp e developed significantly faster than the B-biotype on S. nigrum and D. str amonium. Both biotypes required, for this development, significantly more d ays on D. stramonium than on S. nigrum. These results suggest that it is im portant to suppress the growth of M. parviflora, C. bursa-pastoris, B. kabe r, D. stramonium and S. nigrum in order to avoid the risk of further expans ion of whitefly populations where these weeds and both B- an Q-biotypes are present.