2013 Annual Report
1a.Objectives (from AD-416):
To evaluate herbicide and fumigant combinations for broad spectrum pest control in open-field production of perennial (tree, vine, and ornamental) nursery stock in the absence of methyl bromide and transfer knowledge to stakeholders via a cooperative extension program.
1b.Approach (from AD-416):
Field research and demonstration plots will be established in commercial nurseries in the Central Valley of California. Data on control of weeds, nematodes, and soil pathogens of economic or regulatory importance to the tree, vine, and ornamental nursery industry will be evaluated by ARS and UC personnel. Technology transfer efforts to facilitate adoption of methyl bromide alternative pest control strategies will be conducted in cooperation with research and extension faculty and support personnel at the University of California, Davis.
This project addresses the in-house project (NP 211) Objective 5: Develop various application methods, soil amendments, and physical barriers to reduce the emissions and enhance efficacy of the chemical alternatives to methyl bromide. This project was established to demonstrate alternatives to methyl bromide (MB) in key crop systems and regions dependent on MB. This project has a primary focus on open-field production of deciduous tree, grapevine, and garden rose stock in California. This industry contributes over $200 million to the economy of the state and supplies over 60% of the total fruit, nut, and rose plants sold in the USA. In comparison with other fumigation-dependent industries, perennial nursery stock producers may face a more difficult transition to alternatives due to regulatory constraints and adoption of MB alternatives in California nurseries has been slow. For the first few years under this project, more than 10 field trials have been conducted to determine effectiveness of alternative fumigants and herbicides on soil pest control. Although several fumigant treatments were identified for effective control of nematodes and pathogens in some cropping situations, the only MB alternative currently approved for meeting California’s nursery certification requirements is 1,3-dichloropropene (1,3-D) [e.g., Telone II and Telone C35]. However, these products are only approved for use in nurseries with coarse-textured soils because the maximum rate allowed in California (332 lb/A) is not sufficient to provide adequate pest control in fine-textured soils. Thus, the various field trials were to address the issues limiting adoption of methyl bromide alternatives in California’s perennial crop nursery industry. Towards the end of this project, research and outreach efforts have been focusing on reporting research results and extending information to growers, scientists, and regulatory agencies. Information from this project and related MB alternatives research was disseminated through scientific and extension channels. Scientific reports included a vineyard and grape nursery fumigation paper published in Pest Management Science (Cabrera et al. 2012), a cut flower nursery paper published in Hort Technology (Rainbolt et al. 2012), a nursery herbicide paper submitted to Hort Technology (Abit and Hanson, in press) as well as contributions to four summary articles submitted to the journal California Agriculture (Gao et al.; Browne et al., Cabrera et al., and Hanson et al.; all accepted for publication). Finally, the information generated in this nursery project was used during the development of a template for a multi-state, multi-investigator outreach website tying back to the goals of the Pacific Area-Wide Program for Integrated Methyl Bromide Alternatives. The perennial nursery portion of the website can be accessed at http://ucanr.edu/sites/PAWMBA/Nursery_Projects/Perennial/.
To summarize, a number of technical and regulatory challenges limit the adoption of methyl bromide alternatives by the perennial crop nursery industry. The nursery certification program and other regulations also limit the alternatives available to the perennial nursery industry. Of the fumigants registered in the state, only 1,3-dichloropropene (alone or in combination with chloropicrin or an MITC generator) are approved treatments in nurseries with medium- to coarse-textured soils. Unfortunately, no viable alternatives exist for California nurseries with fine-textured soil; absent new alternatives or changing regulations, some of these operations may be unable to produce certified nursery stock in the complete absence of methyl bromide. Compared to some other fumigation-dependant industries, perennial fruit and nut nursery producers face a more difficult transition to methyl bromide alternatives. Despite several years of research, extremely low tolerances for nematodes, long growing cycles, as well as technical and regulatory hurdles continue to be significant challenges to widespread adoption of methyl bromide alternatives in the perennial crop nursery industry. While significant challenges remain for this industry, we encourage a full evaluation of the risks and benefits of nursery fumigation on the productivity of perennial cropping systems around the world.