Submitted to: Biopesticides International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2006
Publication Date: 3/15/2006
Citation: Kremer, R.J. 2006. The role of bioherbicides in weed management. Biopesticides International. 1(4):127-141.
Interpretive Summary: Farmers consider weeds that infest and compete with crops as the most serious pest problems they encounter annually despite the availability of potent herbicides and genetically-modified, herbicide-resistant crop varieties for modern weed management. Factors that contribute to constant weed problems include the development of herbicide-resistant weed types; newly invasive weeds that are not controlled by current herbicides; and loss of herbicide effectiveness by inactivation by soil components (i.e., clays, organic materials) or rapid degradation by microorganisms. Bioherbicides, which are natural products formulated with living microbial pathogens that selectively infect certain weeds, may potentially reduce the severity of weed problems that interfere in crop production. The objectives of this report were to identify the role of bioherbicides for integration into weed management programs and to improve the understanding of the factors that affect their implementation in crop production systems. The most successful bioherbicides are those developed for very specific weeds in small-scale or specialized cropping systems (i.e., bioherbicide that attacks the parasitic weed, dodder, in cranberry). Also, traditional bioherbicides target single weed species and require special formulations to assure viability and pathogenicity of the microbial agent. Limitations such as these must be overcome for application of bioherbicides to a broader range of crops. Use of multiple pathogens to increase the spectrum of weeds attacked by bioherbicides and combination of bioherbicides with conventional herbicides may improve management of weeds difficult to control with herbicides. As more bioherbicides are developed for effectively controlling parasitic, herbicide-resistant, and exotic invasive weeds, their potential value as part of integrated weed management in both conventional and sustainable agricultural systems will be realized. The information presented in this paper provides a practical summary on bioherbicide development and potential applications useful to biocontrol and weed scientists, industrial scientists, extension personnel, and crop farmers. The information will be helpful to those involved in developing strategies not only for new bioherbicides but also for total weed management programs in which bioherbicides might be an effective component.
Technical Abstract: The bioherbicide approach to weed management involves the release of high numbers of selected microorganisms for attacking specific weeds and controlling the weed infestation within the same year of application. Ideally, bioherbicides are most effective for weed management in annual cropping systems that are unsuitable for a classical biological control strategy, which involves the use of natural enemies that require more than one year to develop effective, weed suppressive populations. Currently, only a few bioherbicides are successful in field-scale control of weeds; the effectiveness of other bioherbicides has been limited by restricted host-range, elaborate formulation requirements, and lack of persistence in the field. Bioherbicides may be most effective for management of weeds that are considered herbicide-resistant, parasitic, or invasive. Based on the current status of bioherbicide use, strategies for widening host ranges, improving formulations for practical use, and improving techniques for enhancement of weed-suppressive activity in conventional and sustainable agricultural systems are needed if this biological control strategy is to significantly contribute to non-chemical weed management.