Biocontrol of plant diseases: the approach for tomorrow

Abstract

More than 50% of crop loss in the United States is due to diseases caused by microbes inhabiting the soil. Biocontrol represents an attractive alternative for the future because of the many concerns about pesticide use. Recent advances from our laboratory on soil-borne disease control are: (a) development of biocontrol formulation systems for delivery, (b) genetic manipulation of biocontrol agents to increase their efficacy, and (c) the use of biocontrol in integrated pest management. For dust formulations, dry biomass of Trichoderma and Gliocladium, produced by deep-tank fermentation of readily available, inexpensive agricultural wastes, was milled and mixed with inert carriers for application to soils. Dry or wet biomass was also immobilized into granular pellets, which may contain a food base to allow the biocontrol fungi to grow. These innovative formulations, easily adapted to commercialization, include alginate, carrageenan, and chitosan pellets. A new approach to activate biocontrol fungi in a vermiculite/bran preparation was also developed. In another novel approach, biotypes of Trichoderma and Gliocladium were developed which possessed enhanced biocontrol ability or were tolerant to chemicals used in agriculture. The genetic manipulation was achieved with chemical and ultraviolet mutagenesis, or transformation. Studies are also in progress to understand the mechanism of action of certain effective biocontrol fungi.