Fusarium wilt and Southern Blight Diseases of Tomatoes: Trichoderma spp. as Antagonists of the Causative Organisms

Fusarium wilt ( Fusarium oxysporum f. sp . lycopersici ) and southern blight ( Sclerotium rolfsii ) are two of the soil borne diseases limiting tomato cultivation globally and are difficult to manage. This study evaluated biocontrol agents, Trichoderma harzianum and T. viride for antagonistic efficacy against these pathogens in vitro . The dual culture technique was adopted using two approaches; namely, pre-inoculation of Trichoderma spp. into culture medium at 24 and 48 hours ahead of the pathogen and simultaneous inoculation of Trichoderma spp. and pathogen. The Trichoderma spp. were evaluated singly against each pathogen. The sole culture of each pathogen was the control. Each treatment was replicated thrice and laid out in a completely randomized design. Inoculated Petri plates were incubated at 27 o C ± 2 o C. Data collected were subjected to statistical analysis and mean separation using Minitab software. Results showed that the inhibition of the mycelial growth of both pathogens by the biocontrol agents were days dependent. Furthermore, prophylactic evaluations gave significantly higher inhibition of the mycelial growth of the pathogens as against therapeutic evaluation. Additionally, F. oxysporum was more susceptible to antagonism by both biocontrol agents as higher percentages of mycelial growth inhibition were recorded for it in all treatments. Finally, T. harzianum was a better antagonist of the two pathogens, recording 84.62% and 69.01% inhibition of mycelial growth of F. oxysporum and S. rolfsii, respectively at 9 days after inoculation. Trichoderma spp . maybe exploited as biocontrol agents for the management of these pathogens.