Field evaluation of selected formulations of Trichoderma species as seed treatment to control damping-off of cowpea caused by <i>Macrophomina phaseolina</i>

Abstract

The experiment was carried out between 1997 and 1998 at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria to test the efficacy of biological seed treatment of cowpea against Macrophomina phaseolina infection in the field. Trichoderma sp., T. koningii Oudem (IMI 361600) and T. harzianum Rifai (IMI 361601) were selected from soil dilutions and tested in vitro for their antagonistic behaviour against cowpea pathogen M. phaseolina before use in the field. The in vitro tests in dixenic cultures, showed all three Trichoderma species growing fast and stopping the growth of the pathogen by the third day of pairing. Two varieties IT86D-2120, and Ife Brown were tested and two formulations of each Trichoderma species (mycelial suspension and suspension + starch) were also tested. The analysis of variance showed that there were significant differences between stands from the two trials and varieties. Treatment effect was also significant. The variety IT86D-2120 had significantly better stands in both trials. The highest plant stand of 53.8% at 7 days after planting (DAP), from the first trial, was from IT86D-2120 seeds treated with T. koningii + starch, which decreased to 49.3% by 21 DAP due to post emergence damping off. In the second trial, IT86D-2120 seeds treated in T. harzianum suspension had percentage stand of 55% at 7 DAP, which reduced to 45.8% at 21 DAP.

Keywords: Trichoderma harzianum, T. koningii; biological control, field trial, Macrophomina phaseolina