Abstract:
BACKGROUND: In Africa, food legumes such as cowpeas and beans constitute important sources of proteins for millions of rural and urban populations. However, attacks by multiple pest species can reduce yields by up to 80%. Smallholder farmers protect their crops against pests using conventional insecticides, thereby contributing to insecticide
resistance and jeopardizing food safety. To date, no alternative sustainable practices are available to reduce insecticide
use in the management of legume pests. This study aimed to provide a sustainable alternative to insecticide use
based on semiochemicals to manage multiple legume pest species and enhance food productivity.
RESULTS: Using coupled gas chromatography-mass spectrometry (GC–MS) and coupled GC-electroantennographic
detection (EAD) analyses, we identified 2-methylbutyl 2-methylbutanoate as the male-produced aggregation pheromone of the legume pest, Clavigralla elongata, a coreid bug species specific to East Africa. In multi-site field trials
conducted in West Africa and East Africa, 2-methylbutyl 2-methylbutanoate and its analogue, isopentyl butanoate,
previously identified from the pan-tropical coreid bug, C. tomentosicollis, both lured multiple legume insect pest species including from the Clavigralla genus, the legume pod-borer Maruca vitrata, fower thrips Megalurothrips sjostedti,
and whitefly Bemisia tabaci into traps. Additionally, both pheromones lured the Clavigralla natural enemy parasitoid
Gryon fulviventris into traps. The whitefly was only captured in pheromone-baited traps in East Africa. Deployment
of an optimized pheromone trapping system significantly reduced legume pests and increased natural enemy density by up to sixfold compared to farmer practice (insecticide-treatment) and control. Legume yields for pheromone
and insecticide treatments were comparable,~320–590% higher than untreated controls.
CONCLUSION: These findings establish coreid bug pheromones as effective novel multifunctional semiochemical-based tools for sustainable legume pest management and production without insecticide use.
