The objective of this study was to evaluate the antagonistic activity of Trichoderma spp. against wild pathogen Fusarium oxysporum F.28.1A, which causes wilt disease on sesame. Twenty-six isolates of Trichoderma spp. isolated from soil samples were tested to control F. oxysporum F.28.1A. Prescreening showed that five isolates were T-02B1, T-18B2, T-20B1, T-28B1, and T-29A1, based on the lowest values of colony radius of F. oxysporum F.28.1A. The selected isolates were identified by their ITS region as T. yunnanense T-02B1, T. lentiforme T-18B2, T. asperellum T-20B1, T. hamatum T-28B1, and T. hamatum T-29A1, with similarities around 96–100%. The isolates selected were able to produce enzymes including chitinase, exo-β-1,3-glucanase, and endo-β-1,3-glucanase at levels of 0.34–0.44, 0.017–0.034, and 0.032–0.121 UI · ml ^–1, respectively, which were considered to be a mechanism to prevent the growth of F. oxysporum F.28.1A. The isolates tested were applied in soil pots to prevent damage from F. oxysporum F.28.1A as a following experiment. The greenhouse experiment was arranged in a completely randomized design with 10 treatments, including a negative control, application of only F. oxysporum F.28.1A, application of both F. oxysporum F.28.1A and fungicide chemicals, application of both F. oxysporum F.28.1A and Trichoderma spp. DHCT, application of T. yunnanense T-02B1, application of T. lentiforme T-18B2, application of T. asperellum T-20B1, application of T. hamatum T-28B1, application of T. hamatum T-29A1 and a mixture of the five selected isolates of Trichoderma spp. with their total population equal to that in individual strain application. The results showed that the five mixed isolates of Trichoderma had a synergistic effect on the reduction of the disease’s prevalence by 35% compared to the negative control treatment.

A survey was conducted in February of 2004 on the outbreak of stem rot and wilt disease of pepper at the Kitabawa/Danzakara and Ajiwa irrigation sites in Northern Nigeria. Laboratory investigations revealed that it was elicited by Phytophthora capsici Leon. The disease caused severe loss in yield and USD 1 700.00 to USD 3 200.00 loss in revenue/ha. The disease was probably further aggravated by the presence of Fusarium sp. as well as ecto- and endoparasitic nematodes. Reasons for outbreak were elucidated and solutions proffered.