BIOLOGICAL-CONTROL OF PYTHIUM DAMPING-OFF OF COTTON WITH SEED-COATING PREPARATIONS OF GLIOCLADIUM-VIRENS

Air-dried and ground seed-coating preparations of Gliocladium virens were variable in their efficacy for biocontrol of cotton seedling disease induced by Pythium ultimum. Disease suppression was dependent on the proper strain-substrate combination and on the amount of material used. Treatment in excess of that required to coat the seed resulted in phytotoxicity. The loss of disease suppression with time in open storage in the lab was associated with a diminution in the amount of antifungal gliovirin in the preparation and a lengthening of time for propagule germination of the biocontrol agent. Combination treatments with reduced levels of metalaxyl fungicide and the biocontrol preparation resulted in a synergistic effect that gave disease suppression equal to that of full-strength fungicide treatment. Seed coat preparations of G. virens may be used to control Pythium damping-off of cotton seedlings, and in combination with fungicide, the amount of fungicide necessary to effect control can be reduced.