Submitted to: CABI(Council of Applied Biology International, Oxford, United Kingdom
Publication Type: Book / Chapter
Publication Acceptance Date: January 25, 2007
Publication Date: August 6, 2007
Citation: Weaver, M.A., Lyn, M.E., Boyette, C.D., Hoagland, R.E. 2007. Bioherbicides for Weed Control. CAB International. (Upadhyaya and Blackshaw). Chapter 7 pp. 93-110. Technical Abstract: Following the first commercially successfully biological control of weeds with fungal pathogens a model for a good bioherbicide was developed. It was assumed that a good agent was one that could be grown cheaply and quickly; was aggressive and patentable; could be easily applied; had single-weed specificity; and that if satisfactory control was not realized, then the pathogen could be applied inundatively. Some of these principles are still valid, but other portions of the dogma have been effectively challenged. While a highly specific pathogen has a desirable and intrinsic safety, economic realities may prevent such a pathogen from commercialization. This premium on the safety of specific agents may be unwarranted. Numerous successful synthetic herbicides with very broad activities have been safely used. It may be possible to use broad spectrum pathogens with acceptable non-target effects. Broad spectrum bioherbicides such as Myrothecium verrucaria, and Sclerotinia sclerotiorum, might be made 'safe' through deployment strategies or development of ecologically impaired strains, respectively. Other pathogens with low virulence, but with desirable specificity or epidemiology might be made more virulent through genetic modification. Synergy between pathogens and synthetic herbicides may enable the pathogens to be used safely and economically. The philosophy of very high inoculum rates has been largely rejected due to economic limitations and an understanding that better formulation and application technology is more efficient. Through pragmatic understanding of the constraints of economics and safety, intelligent use of formulation and deployment methods and with genetic engineering, the pathogen discoveries of the past might be harnessed as the bioherbicides of the future.