ESTERASE ELECTROPHORETIC VARIATION IN BEMISIA-TABACI (GENN) (HOM, ALEYRODIDAE) AMONG HOST PLANTS AND LOCALITIES IN ISRAEL

This report summarizes 3 years' research on electrophoretic variation in populations of the whitefly, Bemisia tabaci (Genn.) in Israel. This is part of a cooperative project involving Israeli and Colombian scientists. Only one polymorphic esterase locus was examined in detail in this study. Considerable and significant heterogeneity in Esterase allele frequencies was found among samples from different hosts and localities, but there was no pattern of differentiation at this locus according to host plant or to geography. Instead, there was a clear difference in frequency of the fast and slow alleles between samples from insecticide-treated commercial fields and samples from unsprayed control populations: the control populations were almost fixed for the fast allele while the field populations were predominantly slow. The fast and slow isozymes differed also with respect to substrate affinity. It is unclear whether this difference results from selection of certain EST genotypes by insecticide application or from an effect of the pesticide(s) on the EST isozymes in individual whiteflies.