Biocontrol

Abstract

Biological control of weeds involves the use of natural enemies that suppress or reduce parasite populations. Biocontrol of parasitic weeds with insects has not yielded desired results. The seed-eating fly, Phytomyza orobanchia, and the seed gall weevil, Smicronyx spp., are unable to substantially reduce parasitic weed populations due to the tremendous reproductive capacities and the resilient seed banks of the parasites, but in combination with other control methods, these insects might help prevent further dissemination of the parasites. Bacteria and fungi, including arbuscular mycorrhizal fungi, from the rhizosphere of parasitic weeds have been implicated in seed mortality, germination inhibition, reduced parasite establishment, and reduced crop yield loss. Some also produce phytotoxic metabolites that could be precursors to biorational herbicide development. Several Fusarium isolates present the greatest opportunity for controlling parasitic weeds if efforts to increase virulence are realized. Isolates of Fusarium oxysporum f. sp. strigae are proceeding towards commercialization as bioherbicides for Striga hermonthica control.