Host-Parasitoid Interaction Between Lysiphlebus fabarum and Aphis fabae: Parasitism Rate and Developmental Biology

Abstract

The black bean aphid, Aphis fabae, is a destructive sap-sucking pest affecting leguminous and several horticultural crops, while its primary parasitoid Lysiphlebus fabarum plays a crucial role in natural population regulation. The present study investigates the host–parasitoid interaction between L. fabarum and A. fabae, focusing on parasitism rate and developmental biology under controlled laboratory conditions. Aphid colonies were exposed to mated female parasitoids at varying host densities, and parasitism levels, mummy formation, emergence rate, and developmental duration were recorded. Results indicated that parasitism rate increased with host density up to an optimal threshold, beyond which it stabilized due to parasitoid handling limitations. Developmental biology studies revealed that L. fabarum completed its life cycle within aphid hosts, with distinct stages including egg, larval instars, prepupal, and pupal development occurring inside the aphid body, leading to characteristic mummy formation. Developmental duration varied slightly with environmental conditions, with moderate temperature and high humidity favoring faster parasitoid development and higher emergence success. Host size and density significantly influenced parasitoid performance, with larger and more abundant aphid populations supporting higher parasitoid productivity. Mortality of A. fabae was strongly correlated with parasitoid exposure time, indicating efficient host suppression capability. The study highlights the strong regulatory potential of L. fabarum in suppressing A. fabae populations and underscores its importance in biological control programs. Overall, the findings demonstrate a well-defined host–parasitoid relationship characterized by density-dependent parasitism and efficient developmental adaptation of the parasitoid within its aphid host, supporting its integration into sustainable pest management strategies in agroecosystems.