STUDIES ON SCLEROTIUM RQLFSII SACC. ON CROP PLANTS IN NORTHERN NIGERIA WITH SPECIAL EMPHASIS ON TOMATO

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STUDIES ON SCLEROTIUM RQLFSII SACC. ON CROP PLANTS IN NORTHERN NIGERIA WITH SPECIAL EMPHASIS ON TOMATO

Abstract:

Field survey conducted over a period of five years (1976 – 1981) in parts of northern Nigeria during this study, indicate that crops such as tomato (Lycopersicon esculentum), cabbage (Brassica oleraceae) and pumpkin (Cugurbita moschata) were attacked in the field by Sclerotium rolfsii, while others such as onion (Allium cepa) bulbs and potato (Solanum tuberosum) tubers were attacked in storage. Results of field surveys suggest that tomato plant was frequently attacked by the pathogen in the field. Artificial inoculation in the greenhouse showed that all 35 tomato cultivars evaluated were susceptible to infection by S. rolfsii. Of the 40 different plant species screened for susceptibility to infection by the pathogen, only ‘bahama’ grass (Cynodon dactylon) appeared to be resistant to infection by S. rolfsii. Results of field surveys and artificial inoculations in the greenhouse appear to have shown for the first time in Nigeria that cabbage (B. oleraceae), spinach (Amaranthus sp.), sorghum (Sorghum vulgare) and millet (Penniseturn typhoides) are attacked by the basal stem rot disease. Results of in vitro screening of 26 fungicides against S. rolfsii revealed that 13 of these fungicides, notable the oxanthiin compound – Vitavax-, Du-Ter 50, PCNB, Verdasan, Fernasan D and Cerosan practically prevented any mycelial growth at active ingredient concentrations as low as 5 to 50 p.p.m. In vivo greenhouse tests showed that of the fungicides which strongly inhibited the mycelial growth of S. rolfsii on PDA, seven (Aatopam-N, captan, Dithane M-45, Aldrex T, PCNB, Calixin M and captafol) appeared to be non-phytotoxic to young tomato plants at the concentrations inhibiting mycelial growth. An evaluation of the various factors which influence the development of the basal stem rot disease in the greenhouse revealed that pre—inoculation mechanical injury on tomato plants as well as low relative humidity significantly enhanced disease severity. Trichoderma viride completely prevented the appearance of the disease when it was inoculated on tomato plants on the same day as, or three days before inoculation with S. rolf sii, but was ineffective when inoculated three days after inoculation with the pathogen. PCNB was also found to be efficacious in reducing the basal stem rot disease when applied to soil 10 days before inoculation in the greenhouse. In field trials conducted in Samaru to evaluate the efficacy of of some fungicides, antagonistic micro-organisms and animal manures in reducing the basal stem rot disease on tomato, PCNB and T. viride were found to be highly effective in reducing the disease.

STUDIES ON SCLEROTIUM RQLFSII SACC. ON CROP PLANTS IN NORTHERN NIGERIA WITH SPECIAL EMPHASIS ON TOMATO

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