Effects of a plant resistance protein on parasitism of the common bean bruchid Acanthoscelides obtectus (Coleoptera: Bruchidae) by its natural enemy Dinarmus basalis (Hymenoptera: Pteromalidae)

Dinarmus basalis is an important larval parasitoid of the bean bruchid Acanthoscelides obtectus, a major pest of stored legumes throughout the tropical belt. The use of a combination of different natural resources for protecting stored beans from attack by A. obtectus by non-toxic means is considered a promising alternative to the use of traditional chemical insecticides. The seed storage protein arcelin causes sub-lethal effects on the development of A. obtectus that are favorable for biological control. The present study aimed to validate the mutual compatibility between the plant resistance factor arcelin and the biological control candidate D. basalis. Development and performance of D. basalis attacking A. obtectus on beans with different relative arcelin concentrations were investigated in bioassays. The parasitoid accepted hosts on all tested bean lines, irrespective of the relative concentration of arcelin. No indications were found for an effect of arcelin on parasitoid offspring fitness. The parasitoid’s capability to suppress bruchid development was investigated in a follow-up experiment mimicking the temporal complexity of bruchid infestations in the field. Bruchid suppression was significantly higher on arcelin containing bean lines than on arcelin-free cultivars. Our findings demonstrate the potential of the candidate biological control agent D. basalis to contribute to a marked reduction of bruchid emergence in a proposed two-component integrated pest management system.