A review of the non-target effects of fungi used to biologically control plant diseases

Abstract

Biological control agents for plant diseases are currently being examined as alternatives to synthetic pesticides due to their perceived increased level of safety and minimal environmental impacts. Fungal biological control agents have several mechanisms of action that allow them to control pathogens, including mycoparasitism, production of antibiotics or enzymes, competition for nutrients and the induction of plant host defences. While effective in the control of plant diseases, these mechanisms may pose risks to non-target species including mycorrhizal and saprophytic fungi, soil bacteria, plants, insects, aquatic and terrestrial animals, and humans. Non-target effects including mycoparasitism of mycorrhizae, reduction in plant root colonisation by mycorrhizal fungi, disorders in commercial mushrooms and nodulation by Rhizobium spp., and changes in plant growth have been associated with fungal biological control agents, such as Trichoderma spp. Also, the genera Trichoderma and Gliocladium have been linked to respiratory disorders and shellfish toxicity in humans, respectively. Biological control agents, such as Pythium oligandrum, Talaromyces flavus, Coniothyrium minitans and Ampelomyces quisqualis have modes of action which may pose risks to non-target fungi, bacteria, plants and animals. There is need for future research into ecological impacts associated with the release of any biological agent and methods of determining possible non-target effects. Adequate monitoring and the use of molecular techniques to identify and follow the movement of biological control agents are needed to examine and mitigate negative biological impacts.