Yield Losses in Field Beans Following Foliar Damage by Ootheca bennigseni (Coleoptera: Chrysomelidae)

Abstract

The effects of the foliar beetle, Ootheca bennigseni (Weise), infestation on seed yield of some cultivars of field beans ( Phaseolus vulgaris L.) were studied. In the absence of insecticide protection during pref lowering growth stage, cv. Selian Wonder and Masonga, suffered high yield losses and were considered susceptible to O. bennigseni. Cultivar T8 and Mexican 142 had comparatively lower damage ratings of 1.31 and 1.38, respectively, compared with 2.26 and 2.56 for ‘Selian Wonder’ and ‘Masonga’ on a 0 to 5 damage scale, and were considered resistant. Nonpreference and tolerance were the mechanisms of resistance in the resistant cultivars. Bean seed yield losses from 18 to 31% resulted from foliar damage by O. bennigseni. Although the yields in ‘T8’ and ‘Mexican 142’ were significantly higher than those in susceptible cultivars, there was an increase in the yield when these cultivars were sprayed with insecticides because of their resistance to O. bennigseni. These data suggest that for resistant cultivars, one or two sprays can appreciably reduce foliar damage by O. bennigseni and increase seed yields.