Microbial Biopesticides: Yeast

A variety of yeasts have been investigated for their usefulness in controlling plant diseases. Non-pathogenic Cryptococcus and Candida species naturally occur on plant tissues and in water. Isolates from a variety of crops have been investigated for their biocontrol capacities.

For example, Candida oleophila Strain O, first isolated from golden delicious apples, has been developed into an effective biopesticide for the control of post-harvest fruit rots. It is applied to apples and pears after harvest — but before storage — to control particular fungal pathogens. The yeast serves as an antagonist to fungal pathogens such as gray mold (Botrytis cinerea) and blue mold (Penicillium expansum), which cause post-harvest decay.

Candida oleophila Strain O works primarily through competition for nutrients and pre-colonization of plant wound sites. However, there is evidence that it produces enzymes that can degrade fungal cell walls and stimulate plant host defense pathways in freshly harvested fruit, both of which may also make a restricted contribution to the strain’s antagonistic activity.