Evaluation of bean cultivars for resistance to beanflies in single plantings at different seasons

Abstract

Seven selected cultivare of common beans Phaseolus vulgaris L. were evaluated for resistance at two sites under different weather and beanfly population pressures in the field. The indices of resistance were the number of leaf punctures, eggs, larvae and puparia and per cent dead plants. Beanfly species, Ophiomyia spencerella (Greathead) and Ophiomyia phaseoli (Tryon) infested the bean plants in the field. There were seasonal differences in the response of the cultivare to beanfly infestation attributed to differences in the level of attack of the bean crop, being highest in the non-cropping season of 1985 and lowest in the long rains of 1985. Despite the variation in results, Gip 1004 and Gip x-92 showed some resistance on the basis of their least plant mortalities and low larvae/puparia surviving on them. When the beanfly population was high enough to cause death of the bean plants, percentage plant mortality was correlated to the numbers of larvae and puparia of beanflies and it may be the best parameter for resistance.