Biological Control of Fusarium spp. in Cotton, Wheat and Muskmelon by Trichoderma harzianum

Abstract A new isolate of Trichoderma harzianum (T‐35) was isolated from the rhizosphere of cotton plants from a field infested with Fusarium. Under glasshouse conditions, the antagonist was applied to soil growing in a bran/peat mixture (1:1, v/v) or as a conidial suspension or used as a seed coating. When T. harzianum was tested against Fusarium oxysporum f. sp. vasinfectum, F. oxysporum f. sp. melonis or F. roseum‘Culmorum”, a significant disease reduction, was obtained in cotton, melon and wheat, respectively. Biological control of Fusarium wilt of cotton was achieved when tested at two inoculum levels of the pathogen (2 × 107 and 2 × 108 microconidia/kg soil), decreasing the Fusarium spp. soil population. The long term effect of T. harzianum on Fusarium wilt of cotton was studied using successive plantings. The antagonist persisted in soil throughout three consecutive plantings, reducing the Fusarium, wilt incidence in each growth cycle. At the first planting the largest amount of preparation was found superior, whereas at the third planting, no significant difference could be observed between the four rates of Trichoderma preparation. T. harzianum (T‐35) controlled Fusarium wilt in cotton and muskmelon when applied in both naturally or artificially infested alluvial vertisol and sandy‐loam soils, respectively. Soil or seed treatments with the antagonist provided a similar disease control of F. roseum‘Culmorum’ and of F. oxysporum f. sp. melonis.