Resistance to the Mexican Bean Beetle in Several Bean Genera and Species

Nine Phaseolus species, the cowpea (Vigna sinensis (Torner) Savi), the broad bean (Vicia faba L.), the soybean (Glycine max (L.) Merrill), and the Bonavist bean (Dolichos lablab L.) varied in resistance to the Mexican bean beetle (Epilachna varivestis Muls.). Phaseolus aureus Roxb., P. mungo L., P. calcaratus Roxb., P. radiatus L., P. atropurpureus DC., P. lathyroides L., P. polystachyus L., Glycine max, Vicia faba, Dolichos lablab, and Vigna sinensis lines exhibited varying degrees of resistance to beetle-feeding damage under field conditions. All Phaseolus vulgaris L. lines, one Phaseolus acutifolius A. Gray line, and the progenies of interspecific Phaseolus crosses were susceptible. Phaseolus lunatus lines ranged from intermediate in resistance to susceptible. Two methods, larval counts and a visual rating of leaf feeding damage, were compared in evaluating the various lines for resistance to the bean beetle. The visual rating method was found to be as satisfactory as larval counts. Mean maturity dates were associated with resistance in Phaseolus spp., the fewer days to maturity the lower the leaf. feeding resistance exhibited.