Improved herbicide efficacy for organically grown vegetables

Natural weed control alternatives that are currently approved for organic crop production are mostly nonselective essential oils used as postemergence, burn-down products. Their low efficacy requires multiple applications of high volumes to achieve good weed control. Natural herbicides approved for organic use lack systemic activity and have a nonspecific mode of action. There is, therefore, a need for new natural weed control products. This research evaluated improved biological and lower-risk herbicides that are appropriate for use by organic growers to provide enhanced weed management in organic crop production. These included manuka oil and Opportune. Natural triketones present in manuka oil have the same molecular target as some commercial synthetic herbicides. Opportune is a new organic bioherbicide based on thaxtomin, a phytotoxin derived from Streptomyces scabies. The objective of this research was to make available organically acceptable products from novel biological sources to control weeds in organic crop production by developing data on efficacy and crop safety for these products. The synergy associated with tank-mix applications of manuka oil with currently approved essential oils and acetic acid was demonstrated. Weed control with manuka oil, tank-mixed with Green Match EX, Weed Zap, or Weed Pharm was excellent, generally ranging from 90 to 95 % control. This synergy resulted in a 20 to 25 % improvement in overall weed control, compared to each product used alone. This is the key finding from this study and is of great importance to organic growers. This synergy has the potential to significantly improve weed management and will help growers to find solutions to the long standing issue of managing weeds in organic crop production. This research demonstrated novel uses for bioactive natural products to provide organic growers and the public with environmentally and economically sustainable alternatives to synthetic chemical herbicides. This represents an important step in fulfilling society’s desire for reduced dependence on synthetic chemical inputs. It will also serve as an important component for integrated weed management systems for organic agriculture. An integrated approach is the foundation of successful weed management. Improved weed management for organic crop production will help growers respond to the growing demand for organically produced food.