Efficacy of Bio-enriched Vermicompost as Organic Amendment in Suppressing Tomato Wilts Incited by Fusarium oxysporum f. sp. Lycopersici

Fusarium wilt of tomato is a soil-borne disease threatening tomato production in the Savannah ecological zone of Nigeria. Management of the disease using conventional strategies such as the use of resistant cultivars, crop rotation and synthetic fungicides has not always been effective. These necessitate the search for novel alternatives such as the use of vermicompost as organic amendment to control the disease. This work was designed to evaluate the efficacy of vermicompost-amended soil as eco-friendly way of managing Fusarium wilts in tomatoes. The field experiment was 2 x 5 factorial, laid out in a split-plot design with Roma-VF (a resistant variety) and UC 82B (a susceptible variety) allocated to the main plots. The sub-plots contained five treatments: Bio-enriched vermicomposted poultry manure (BIVPO), cowdung-based bio-enriched vermicompost (BIVCO) and Bio-enriched vermicomposted rice bran (BIVRI); CAMAZEB^® as a check and un-amended soil (control). All treatments were replicated three times. The results showed that the incidence and severity of Fusarium wilt were significantly lower on Roma VF than on UC 82B. Application of BIVPO significantly reduced the incidence and severity of Fusarium wilt comparable to the synthetic fungicide CAMAZEB^® at the early stage of the disease development and better than the fungicide at the latter stage. Fusarium wilt incidence and severity were higher in 2015 than in 2016 because of the low pathogen inoculum mitigated by the application of bio-enriched vermicomposts in the preceding year. Use of Roma-VF and BIVPO recorded lower disease incidence (38.7%) and severity (20.4%), and had higher disease reduction (30.8%) and lower stem vascular discolouration (2.5) than the other treatments. This is comparable to growing Roma-VF on BIVCO-amended soil which also recorded statistically similar results. The effectiveness of Roma-VF on BIVPO or BIVCO-amended soil is attributable to low phytotoxicity, abundant soil nutrients and the presence of bio-control agents which improved tomato growth and protection against Fusarium wilt. Roma VF could be recommended to be grown on soil amended with 25 tonnes ha^-1 of BIVPO or BIVCO as an eco-friendly integrated method for the management of tomato wilts caused by Fusarium oxysporum f. sp. lycopersici.