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Foliar biopesticides: Mechanisms, strengths, and limitations.
S. ZHANG (1). (1) Tropical Research and Education Center, University of Florida, Homestead, FL, U.S.A.

Biological control by biopesticides is an important component of integrated pest management and provides alternatives to the use of conventional chemicals. Prevention of pathogen infection or suppression of disease by biocontrol agents is contingent on their modes of action. It is well known that competition for nutrients and space by biocontrol agents is an important mechanism because certain pathogens are negatively infected by lack of nutrients in the infection court. Antibiosis and hyperparasitism are other mechanisms by which many pathogens are adversely affected. Resistance in host plants may be induced locally or systemically by live cells or dead cells of biocontrol agents, and induced resistance is usually effective against different pathogens. Reduction of the saprophytic ability and reducing spore dissemination by biocontrol agents are among other mechanisms. Lately, it is revealed that repressing pathogenicity factors of the pathogens is responsible for biocontrol. Practically, large-scale use of biocontrol particularly in the field is still limited because of inconsistency of performance. To improve the performance of biocontrol, integration of biocontrol with chemicals or application of mixed biocontrol agents each with different modes of action would be a promise. The overall goal of these suggested strategies is to reduce risk of uncontrolled disease epidemics and to increase confidence of growers in using biocontrol.

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