Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2000
Publication Date: N/A
Technical Abstract: Development and rapid acceptance of biological control systems are challenged by factors limiting the spectrum of activity, efficacy, and reliability. Effectiveness of biological control may be best demonstrated as a component in an overall biological weed management system. Cover crops and mulches may be used for integrating biological control agents by promoting establishment in soils for attack of weed seeds. Several cover crops alone and combined with selected deleterious rhizobacteria (DRB) were evaluated. In each of three years of the study, cereal grain cover crops reduced weed biomass 90% compared to weedy checks. Brassica cover crops and sweet clover reduced weed biomass to a greater extent when combined with soil-applied DRB. DRB marked with antibiotic resistance were detected on roots of cover crops and established high soil populations for colonization of periodically-germinating weed seedlings and subsequent weed dgrowth suppression. Rhizosphere colonization by DRB varied among cover crops indicating specificity, useful in selecting cover crop-DRB combinations. Results implicated allelopathic activity of specific plant species combined with phytotoxic effects of DRB caused greater weed seedling growth suppression compared to either approach alone. In 1998 soybean planted into several cover crop residues without herbicides gave seed yields higher than the weedy check and equivalent to soybean grown with conventional weed control. Weed suppression was further enhanced when DRB were included. Integration of nonchemical weed management methods has potential in reducing herbicide use and enhancing efficacy of biological weed management.