Low Levels of Resistance to the Mexican Bean Weevil in Dry Beans1

Abstract

Low levels of resistance were detected among more than 4,000 accessions of dry beans, Phaseolus vulgaris L., exposed to Zabrotes subfasciatus (Boheman). Although significant differences were found among the accessions for all of the parameters of resistance measured, most consistent separation among cultivars was obtained by using developmental time and weight of adult progeny. Expression of resistance was maintained when the number of bean seeds per adult was varied; however, the standard method used (seven pairs of adults infesting 50 seeds) was the best infestation level to detect varietal differences in resistance. Successive rearing for five generations on resistant or susceptible classified entries did not change resistance expression or reduce reproduction of Z. subfasciatus on resistant lines. Resistance levels were too low to be of economic value.