Efficacy of Bacillus subtilis and Trichoderma asperellum against Pythium
aphanidermatum in tomatoes
Seedling damping-off disease caused by Pythium aphanidermatum is the most important seedling disease
in tomato production in Kenya. The disease causes seedling losses of up to 30%. Greenhouse trials were
conducted to evaluate the application of Bacillus subtilis and Trichoderma asperellum, as seed coating for
management of damping-off in tomato from April 2011 to August 2014. Tomato seeds (var. Rio Grande)
were coated with either B. subtilis or T. asperellum at a concentration of 106 CFU/ml. The interaction
between the two biocontrol agents and NPK fertilizer was assessed. To simulate the effect of high disease
pressure, the coated seeds were planted in P. aphanidermatum inoculated media. The post-emergence
seedling damping-off on seeds coated with B. subtilis and T. asperellum was 20.19% and 24.07% respectively
while the control (non-coated) had 65.89% seedling mortality. A combination of NPK fertilizer
and biocontrols in seedling management resulted to a significantly higher dry mass compared to the
use of either biocontrol agent or fertilizer alone (P 6 0.001). This study indicates that coating of tomato
seeds with B. subtilis and T. asperellum may be useful in the management of damping-off disease.
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