BackgroundBacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases in tomato cultivation. This study aimed to evaluate the effect of Bacillus and Trichoderma isolates to manage the bacterial wilt disease.Main body of the abstractField experiments were conducted in a randomized complete block design at Mwea and Kabete sites in Kenya. The treatments included 3 Trichoderma; 2 Bacillus isolates; a mixture of T1, T2, and T4; chemical standard; and distilled water as control. Trichoderma and Bacillus isolates were grown on sterilized sorghum grain and cow manure carriers respectively. Antagonist’s inoculation was carried out by dipping tomato plants for 30 min in each treatment suspension. Each treatment was then applied at a rate of 150 ml/plant hole and this was repeated after 35 days. All the treatments significantly reduced bacterial wilt incidence and severity at P ≤ 0.05 than the control at both sites. Trichoderma isolate T1, followed by Bacillus isolate CB64, was the best in reducing the disease incidence by more than 61.66 and 53%, respectively at both sites. Treatment CB64 and T1 had the highest reduction of R. solanacearum population in the soil by 93.17 and 92.07%, respectively. However, control had a pathogen increase of 20.40%. CB64 and T1 performed significantly better compared to the standard, while the mixture of isolates T1, T2, and T4 performed the poorest in all parameters. The treatments also increased the yield of tomato.Short conclusionResults from this study showed that Trichoderma and Bacillus isolates are effective biological control agents for use in management of bacterial wilt.