Incidence and Damage of Bruchid Infestation on Selected Common Bean Varieties under Farmers’ Storage Conditions in Burundi

Abstract

Common bean (Phaseolus vulgaris L.) is a vital legume crop globally, providing essential proteins and micronutrients, particularly in developing countries. In Burundi, beans are integral to food security and rural livelihoods, yet smallholder storage practices expose seeds to significant postharvest losses, primarily from the bruchid pests Acanthoscelides obtectus and Zabrotes subfasciatus. Despite the economic importance of beans, limited research has systematically evaluated varietal resistance patterns and storage dynamics under realistic smallholder conditions across different agro-ecological zones in Burundi. This study evaluated the effects of storage duration, environmental conditions, and varietal resistance on bruchid infestation across Burundi's three agroecological zones. Four common bean varieties (Kinure, Mukungugu, Musore, and Gasilida) were monitored monthly over four months (February-May 2025) across six sites in an experiment employing a completely randomised design, with 72 samples and three replications. Parameters measured included seed perforation, bruchid emergence and mortality, and seed weight under typical farmer storage conditions. Storage duration significantly influenced infestation dynamics (p < 0.001) for both bruchid species. Initial storage showed minimal damage (100% unperforated seeds), but deterioration accelerated from April onwards, with A. obtectus perforation reaching 3.75% and Z. subfasciatus perforation reaching 5.13% by May. Live bruchid populations peaked at 68.5% for A. obtectus in April and 94.21% for Z. subfasciatus in March. Significant varietal differences in emerged bruchids were observed (p < 0.001), with Kinure demonstrating superior resistance across all parameters. This variety maintained 99.42% unperforated seeds, the lowest perforation rate (0.58%), the highest seed weight (994.8 g), and the lowest live bruchid population (32.9%) for A. obtectus. Similar patterns occurred with Z. subfasciatus infestation. Conversely, Gasilida and Mukungugu showed greater susceptibility, with higher perforation rates and bruchid populations. Storage site effects were generally non-significant (p > 0.05), indicating that varietal characteristics were more influential than micro-environmental differences across altitudes ranging from 800 m to > 2000 m. The study identifies Kinure as a consistently resistant variety suitable for promoting storage pest management in regional seed systems. The findings validate genetic factors as primary determinants of seed storability and support variety-based approaches to reducing postharvest losses. The integration of resistant varieties with improved storage technologies offers promising pathways for enhancing food security in bean-dependent smallholder communities.