Locally Produced Microbial Inoculants and Plant Bioactive Extracts Reduced Soybean Pest Damage and Improved Biomass Productivity

Abstract

Pest infestation can severely affect soybean productivity, and synthetic pesticides are frequently used to control crop damage, which may cause deleterious effects on the environment and humans, while their misuse can lead to pest resistance. This study evaluated the potential of locally produced bio-inoculants of microbial and plant origins to control bean leaf beetle and pod borer pests, and the impact on soybean growth and biomass production as a sustainable alternative to synthetic pesticides in Buea – Cameroon. Experiments were conducted in August 2021 and repeated on the same plots in April 2022 to compare performance across seasons, while a new site was used in April 2023 to confirm the effectiveness of treatments in similar seasonal conditions. Experiments were established as Randomized Complete Block Design, with thirteen treatments and four replications. Treatments include control–no input, chemical (NPK fertilizer+Lamida gold insecticide), plant growth-promoting bacteria (PGPB1)+endophytic fungi (EF), PGPB2+EF, PGPB1+Piper extract (P), PGPB2+P, Rhizobium (R)+P, R+EF, Mucuna extract (M)+P, M+EF, PGPB1+M+EF+P, PGPB2+M+EF+P, and M+R+EF+P. Results show similar performance of bio-inoculants from microbial or plant origin and synthetic chemicals in reducing beetle infestation, severity and damage by 15–75%, leading to significantly (P<0.05) higher soybean growth and biomass at 15–100% when compared to the untreated control for all experiments. Bean leaf beetle infestation correlated negatively with plant height, number of leaves, leaf area index and soybean biomass (P<0.05). These findings highlight the potential of locally formulated bio-inoculants as a sustainable alternative to synthetic pesticides, which opens up avenues for further research on their mechanism of action that can be explored for biological pest control to enhance soybean performance