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United States Department of Agriculture

Agricultural Research Service

Research Project: SYSTEMS AND TECHNOLOGIES FOR SUSTAINABLE SITE-SPECIFIC SOIL AND CROP MANAGEMENT

Location: Cropping Systems and Water Quality Research

Title: Editorial: Current Status of Bioherbicides

Author
item Kremer, Robert

Submitted to: Tunisia Journal of Plant Protection
Publication Type: Popular Publication
Publication Acceptance Date: March 1, 2008
Publication Date: March 1, 2008
Citation: Kremer, R.J. 2008. Editorial: current status of bioherbicides. Tunisia Journal of Plant Protection. 2(2)ii-iii.

Technical Abstract: Bioherbicides are formulated biological control products for application of massive numbers (inundation) of selected pathogens to attain weed control within one growing season. Bioherbicides were considered potential alternatives to conventional weed control with synthetic herbicides because of better environmental compatibility and lower risks to human and animal health. Thousands of microbial cultures have been screened as potential bioherbicide agents in numerous laboratory, greenhouse, and field studies. However, only a few bioherbicides were fully developed for in-field weed management; many biological control agents remain cataloged but not fully exploited. Thus, deployment of successful and effective biological control products for reducing herbicide use has been extremely limited despite significant inputs of scientific effort, time, and funding into biological control programs. The very nature of bioherbicides as living products that attack specific weeds at a critical growth stage is a major limitation to adoption for use in most cropping systems. The use of a bioherbicide to control one species in a mixture of weeds in the field is questionable if producers have access to broad-spectrum herbicides to control multiple weed species. Unique formulations were developed to assure an optimum environment for bioherbicide pathogens to withstand adverse conditions when applied in the field and promote subsequent infection and disease. The primary purpose of improved formulations was to provide adequate moisture on the weed surface for preventing desiccation of the pathogen during infection and disease initiation. Adequate infection is assured through suspension of massive numbers of pathogen cells formulations. Formulated in this manner, about 10 bioherbicides have been commercialized world-wide for control of specific weeds in specialty crops or defined ecosystems. Improvement is still needed for adaptation of bioherbicides to control multiple weeds in cropping systems. Combinations of ‘core strains’ of pathogens that suppress growth of three or more dominant weed species within a site has been successful on a limited scale. Nutritional manipulation of culture ingredients or nutrients resulted in enhanced virulence of selected biological control pathogens on certain weeds. Genetic enhancement of virulence to overproduce toxins, enzymes, or other metabolites was successfully demonstrated to expand the spectrum of weeds suppressed by the bioherbicide. However, increased public concern about genetically-modified products used in agriculture may limit acceptance of similarly modified bioherbicides. Most bioherbicides only suppress weed growth but do not necessarily completely kill weeds. Whether farmers and landowners will accept visible scattered weeds in fields that would otherwise be weed-free with herbicides is questionable. Bioherbicides may be integrated into conventional cropping systems for control of herbicide-resistant weeds. At least 10 glyphosate-resistant weed biotypes have been reported, ideal targets for future bioherbicides deployed to attack weeds escaping control in transgenic cropping systems. Bioherbicides may be most effective in sustainable agricultural systems receiving organic inputs via various amendments, crop rotation and crop residue management, or cover cropping. Bioherbicides can supplement or enhance natural weed control inherent in sustainable systems through: integration with cover crops; combination with allelopathic crops; and integration with various organic amendments to facilitate or supplement weed control. Considerable opportunity exists for practical application of bioherbicides in agricultural and natural ecosystems. Improvement through virulence enhancement and expanding the spectrum of weed control is critical for adoption in cropping systems. Increasing costs of petroleum-based inputs and gradual integration of sustainable production practices into crop management will drive adoption of effective bioherbicides as components of weed management systems.

Last Modified: 4/20/2014
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