Integrated Clubroot Control Strategies for PNW Brassica Producers

Integrated Clubroot Control Strategies for PNW Brassica Producers

Summary

By the fall of 2016, we will have completed the research phase of the project, and we will focus our future efforts on outreach and education. Research results helped us fine-tune our disease mitigation strategies, as well as identify varieties resistant to the pathogenic race present in western Oregon. Using the European Clubroot Differential set, only race 16/2/30 was identified in this region. Based on this research, we just released (August 2016), the Oregon State University Extension publication Integrated Clubroot Management for Brassicas: Nonchemical control strategies (EM9148) (19 pages; https://catalog.extension.oregonstate.edu/em9148) as well as a clubroot resistant variety guide (http://horticulture.oregonstate.edu/content/vegetable-variety-selection-resources). We will continue our outreach and educational efforts by creating further resources, and marketing them to farmers and industry personnel.

Objectives/Performance Targets

The goal of this project is to provide farmers with the information and resources necessary to implement an effective and economical integrated clubroot management program. The farmer-scientist team will conduct collaborative research and Extension activities:

Objective 1: Conduct on-farm research investigating cultivar resistance to clubroot, and the effectiveness of cultural practices for clubroot suppression. 

Performance Target:  Based on the findings of variety screening, cultural control, and farm rotation studies, we will develop integrated recommendations for clubroot disease management.  

Objective 2: Provide Extension outreach to growers to assist them in developing an integrated approach for clubroot disease control. 

Performance Target:  During the final year of the project, we will assess changes in farmer understanding, intentions, and practices. Farmers will be asked to identify specific practices they have adopted or intend to adopt as the result of this project. For each strategy, farmers will describe 1) whether or not they adopted it or if they intend to adopt it, 2) if it appears to be effective (if they adopted it), and 3) if it is cost effective. Farmers will also be asked how much damage and lost income they experienced due to clubroot before the project, and how much damage and lost income they anticipate after adopting project findings.

Accomplishments/Milestones

By the fall of 2016, our farmer-scientist team will have completed the research component of this project. Work that has been completed to date includes:

• Conducting seven on-farm field research trials with both organic and conventional fresh market and processing brassica growers. Based on grower input, we identified clubroot resistant varieties that may be suitable replacements for susceptible varieties (i.e., have the horticultural characteristics desired by the grower, wholesaler, processor, and the consumer). These trial results helped us fine-tune our disease mitigation strategies, which will aid future growers in implementing a successful control program.
• Identifying the pathogenic race of clubroot present in Oregon’s Willamette Valley using the European Clubroot Differential (ECD) set. Based on the ECD set, only race 16/2/30 was identified, indicating a relatively uniform disease population.
• Screening 24 commercially available varieties from nine crops that have been purported to have disease resistance. This screening was conducted in growers field’s with a history of clubroot, and also in greenhouse studies where a soil/potting mix was inoculated with the disease. Of these 24 varieties, 75% had some level of resistance to the pathogenic race (ECD designation 16/2/30) present in western Oregon.
• Screening Oregon State University’s clubroot resistant germplasm collection to identify varieties that could be used by breeders to create new clubroot resistant varieties. We evaluated three broccoli and three cabbage breeding lines for resistance, of which two broccoli and one cabbage showed resistance.

Impacts and Contributions/Outcomes

When first embarking on this project, a survey was sent to farmers growing brassicas to assess their experience dealing with clubroot. From this survey, gaps in knowledge and available information were identified that would be needed to implement a successful integrated clubroot management program. Based on these survey results, our farmer-scientist team conducted collaborative research which has helped to fill these knowledge and resource gaps. Below is a list of outreach materials produced and activities that have been conducted, as well as changes in farmer practices that have been observed:

• In August 2016, the Oregon State University Extension publication Integrated Clubroot Management for Brassicas: Nonchemical control strategies (EM9148) (19 pages) was published (https://catalog.extension.oregonstate.edu/em9148). Although many other state Extension programs have clubroot management guides, this publication is unique for its in-depth, integrated management approach, as well as detailed step-by-step instructions to implement a successful clubroot liming program (which is different and more challenging than liming for crop production).
• A clubroot resistant variety guide was created that gives the level of resistance as well as notes on horticultural characteristics. This guide is available here: http://horticulture.oregonstate.edu/content/vegetable-variety-selection-resources
• Some of the farmer collaborators have begun to adopt the practices that were researched on their farms to control the disease. These include longer rotations out of brassicas, growing resistant cultivars, and implementing an aggressive liming program.
• Our seed company partners (Osborne Seed, Bejo Seed, Syngenta, and Sakata) are now able to add clubroot resistance information in their product descriptions with confidence. This has included removing claims of clubroot resistance for varieties that showed no resistance to the pathogenic race present in western Oregon.
• In the winter of 2016, an outreach booth was set-up at two conferences (North Willamette Horticultural annual meeting and the Oregon Small Farms Conference) where information was provided on the results of the variety trials. Over 120 seed packets containing resistant varieties for organic and conventional farmers to trial were distributed. This outreach effort resulted in many one-on-one conversations about disease scouting and identification, prevention, containment, and mitigation strategies.

We will continue with our outreach efforts which will include creating an eOrganic webinar and marketing of the educational materials we have produced. We will also send out a survey to participating farmers to assess changes in farmer understanding, intentions, and practices.

Collaborators: