Biological control of weeds with pathogens: Current status and future trends

Considering the implementation of biological control as a modern weed control trend depends primarily on several strategies, most prominently is searching for alternatives to chemical control methods aimed to minimize hazards resulting from herbicide residue on both human and animal health, and on the ecosystem in general. In addition, one of the major strategies of the biological control concept is attempting to incorporate the biological weed control methods as a component of integrated weed management to achieve satisfactory control results and meanwhile, reduce herbicide application to the minimum extent possible. Many pathogens with mycoherbicide Potential have been discovered, but few have become commercial realities or viable alternatives. Biological, technological, and commercial constraints have hindered progress. Many of these constraints are being addressed, but there is a critical need to better understanding the biochemical and physiological aspects of pathogenesis of potential mycoherbicides. Weak links in the host plant's defense need to be exploited and the virulence of pathogens enhanced. In order to make a significant jump forward in formulation, applied research must be evaluated to include fundamental studies of physiological and biochemical changes in cellular organelles and membranes as affected by desiccation and by protections against desiccation. Shelf-life data are worth very little in practical terms for microbial products without data on bioassays and on tolerance to environmental extremes. Environmental tolerance studies and bioassays are essential for monitoring any changes in process. Toxic metabolites produced by fungal pathogens play an important role in host-pathogen interactions. These metabolites consist of a wide array of chemical structures. They can be important factors of pathogenicity or virulence, can have different behaviours with respect to the host varying from strictly host-specific to completely non-specific compounds, and can act with different mechanisms affecting several sites in the host.