The Community Alliance with Family Farmers (CAFF) hosted our second Biologically Integrated Orchard Systems (BIOS) field day at River Garden Farms on November 30th, 2021 titled “Cover Cropping, Sanitation and Mating Disruption in Walnuts.” People came from all over Northern California to learn about the work being done in walnut orchards, many returning after the first BIOS field day. Presentations happened surrounded by farm machinery, including a no-till seed drill, that River Garden uses to plant diverse cover crops every year.
Hanna Kahl, CAFF’s Ecological Pest Management Specialist, started by welcoming attendees and sharing the history of the BIOS project which began in the 1990s and restarted in 2020. The BIOS project encourages farmers to implement a whole systems approach to orchard management that enables farmers to reduce chemical pesticide inputs. Throughout the years the BIOS project has been a collaborative effort that has partnered with farms, pest control advisors and extension organizations, including UC Cooperative Extension and UC Sustainable Agriculture Research and Education Program. In 2020, River Garden Farms became a partner farm in CAFF’s current BIOS project and was the host of Tuesday’s field day.
Hanna summarized the first year of the two BIOS projects: 1) demonstrating the use of mating disruption to manage codling moth and navel orangeworm and 2) the use of cover cropping and release of predatory mites to manage spider mites. Mating disruption can take several years to provide reliable suppression of codling moth and navel orangeworm. However, despite only being the first year of mating disruption use, mating disruption reduced codling moths caught in traps, particularly at farms with high codling moth numbers, and reduced navel orangeworm at all farm sites. Sites with mating disruption also had fewer nuts infested with navel orangeworm. At one of three farms, the release of predatory mites led to establishment of predatory mites and reduction of spider mites. At this farm, cover crops increased spider mite predators near the end of August.
As part of this new iteration and generation of the BIOS program, Dominic Bruno, Assistant General Manager at River Garden Farms, presented on their operation. Attendees were able to learn more about cover cropping and BIOS trials happening at River Garden Farms. Dominic started cover cropping at River Garden Farm four years ago and has continued due to the benefits they have observed from cover cropping. They now cover crop every orchard, resulting in about 500 acres of open ground cover cropped. To find the perfect mix of cover crop seed they have tried a variety of different mixes in their orchards.
Following Dominic’s talk, Jhalendra Rijal, IPM advisor with UC Cooperative Extension, spoke on winter sanitation, focusing on the importance of managing navel orangeworm (NOW) populations. NOW larvae overwinter inside the nuts and this cycle helps establish a population for the next year. In order to combat navel orangeworm, the cycle must be interrupted whenever possible. One solution for this is winter sanitation to remove and shred mummy nuts from trees, which in turn kills the larvae to help prevent increased NOW population the following year.
Our final speakers, Xia Zhu-Barker and Diana Zapata from UC Davis, presented their study focusing on cover crop benefits to soil health. This project has three main goals: understand the impact of cover crops on yield based on three different treatments, understand the impact of cover crops on nitrogen management in the orchard, and identify the cost and return of cover cropping. The study was established at River Garden Farms, and Xia and Diana have worked closely with Dominc Bruno to test effects of three different cover crop treatments: legume, grass and clover, and a multiplex (a mix customized by the growers). They have been evaluating the three different cover crop treatments at River Garden for the past two years, 2019 and 2020. Their findings concluded that cover cropping can help reduce weed biomass, produce organic biomass, and add soil Nitrogen.
Throughout the day, attendees engaged with the presenters and asked many questions about their work and how it could be applied to their fields and orchards. Despite the fog and chilly temperatures, attendees took part in robust discussions with the presenters and each other, wrapping up another successful field day. The BIOS team will continue to host field days throughout the project. Stay tuned for the next field day in Spring 2022!