The consortium operates under the umbrella of ALBA, a worker-supportive operation. This arrangement meets UC insurance, ordering, delivery, and invoicing requirements. When it comes to dealing with a pest infestation—especially of a native pest that can cause significant economic damage—entomologist Sean L. Swezey had some basic advice for his audience at the 2006 Ecological Farming Conference: “Don’t try to spray it into submission. Identify and enhance key natural enemies and get them chomping on it.” Swezey speaks from experience, but in the case of lygus bugs , finding specific natural enemies turned out to be a more complex undertaking than he had imagined. Although a number of lygus predators, such as big-eyed bugs and damsel bugs, occur naturally in the state, Swezey was interested in encouraging a particular type of natural enemy—a selective endoparasitoid that could help control lygus infestations in organic strawberry plantings. Insect endoparasitoids lay their eggs inside their insect host, usually when the pest is in the immature stage. When the parasitoid egg hatches, the developing parasitoid larva kills its host. Because they usually parasitize a narrow range of hosts, endoparasitoids are ideal tools for biocontrol programs. Swezey, an extension specialist with the Center for Agroecology and Sustainable Food Systems ,nft vertical farming has spent years working on alternative cultural control techniques to limit lygus bug damage in organically managed strawberry crops. Finding an effective endoparasitoid to help control lygus populations would be an important biological addition to growers’ management options.
Yet when Swezey and visiting Italian researcher Gianumberto Accinelli from the University of Bologna began searching for a native endoparasitoid of lygus on California’s central coast, they came up empty. “Accinelli reared out literally thousands of lygus and didn’t find a single endoparasite,” recalls Swezey. “An insect like lygus that’s so widespread but has no endoparasitoids affecting the nymphal stage? It was perplexing to say the least.”some unexpected help in his search. “I ran into Charlie Pickett, a biocontrol specialist with the California Department of Food and Agriculture’s Biological Control Program. We started talking about some old scientific literature that described the genus Peristenus [a parasitic wasp] working as a biocontrol agent against the European tarnished plant bug,” recalls Swezey. Pickett had been rearing a parasitoid species of the Peristenus genus that he hoped would help control lygus bug infestations in California’s cotton crop. His research had led him to studies done in southern Europe, where a species very similar to Lygus hesperus infests alfalfa. This pest, the European tarnished plant bug, hosts two naturally occurring endoparasites—the hymenoptera wasps Peristenus stygicus and P. digoneutis. The latter had been successfully imported to the eastern United States where it controlled the tarnished plant bug, a pest of alfalfa. Peristenus wasps attack their prey by parasitizing the nymphal stage of the lygus bug. “The female wasp grasps the lygus nymph, then oviposits [deposits the egg] into a membranous area between two segments of the nymph’s body,” explains Swezey. The developing wasp consumes the nymphal host from the inside out, killing it before emerging as an adult wasp. “A female Peristenus can lay up to 60 or 70 eggs—usually one in each host—in its lifetime,” says Swezey. Working with Dominique Coutinot from the US Department of Agriculture’s European Biological Control Laboratory in Montferrier, France, and Ulli Kuhlman of CABI Bioscience in Switzerland, Pickett imported Peristenus stygicus and P. digoneutis for release in California’s Central Valley.
He was also looking for a cooler region to try and establish the endoparasitoid. “Central Coast strawberry plantings were an ideal study site,” says Swezey.With the help of UC Cooperative Extension farm advisor Mark Bolda, Pickett released the parasitic wasps in 2002 into native vegetation bordering a conventional strawberry operation in Monterey County. “The results were very exciting,” says Pickett, who was surprised to find that the wasps had parasitized 50% of the lygus nymphs collected near the release site—particularly since these were conventional strawberry fields subject to pesticide sprays. “At this point the wasps have most likely become established, and we’ll continue to monitor their spread in the region.” Ronnie Colfer of San Juan Bautista’s Mission Organics identified a second site at Harkins Slough for additional releases.In 2004, Swezey and Center research assistants Janet Bryer and Diego Nieto released both Peristenus stygicus and P. digoneutis into alfalfa plantings established at the Eagle Tree organic strawberry ranch of Pacific Gold in Prunedale . The research group had already conducted several years of field trials at the site, working with Pacific Gold’s Larry Eddings and Joe Valdez to incorporate the alfalfa as “trap crops” in the strawberry fields. These crops attract and “trap” pests such as Lygus hesperus in a concentrated area; ranch personnel then run tractor-mounted vacuums, or “bug vacs” over the strips of alfalfa to remove the lygus bugs. During the 2004 season, the researchers found that approximately 20% of the lygus nymphs they collected from the trap crop had been parasitized by P. stygicus. “We thought that was a big success,” says Swezey. “It told us that you can take the wasp, originally from southern Spain, put them out in this environment, and they successfully parasitize the pest.” The researchers were also surprised to find that 50% of the lygus they collected from a “control” strip of alfalfa 300 meters from the wasp release site had also been parasitized by the wasps. “We probably moved the parasitoid to that strip accidentally, or it may have been moved by the ranch workers or the vacuum machine,” says Swezey.
Nevertheless, the fact that the wasps became established in alfalfa so readily was good news for the research group. After the 2004 season the parasitoids successfully overwintered in the alfalfa plots and were present in the spring of 2005. “That told us that P. stygicus was established in the environment,” says Swezey. Data collected during the 2005 season show a clear “delayed density dependence” of the wasps and lygus population: when the number of lygus in the trap crop and strawberries went up, the parasitism rate by P. stygicus rose soon afterward , and the lygus numbers then dropped. By the end of 2005, parasitism of lygus nymphs in trap crops exceeded 60%. During the 2006 season, the research group will not do any additional wasp releases, but will collect lygus nymphs for analysis to see whether the wasp species continue to spread at the site. The combination of trap crop vacuuming and parasitoid releases has led to a year-to-year decline in average lygus nymph abundance at the Eagle Tree research site since 2003 . Swezey acknowledges that at this point he can’t tease out the effect of the parasites from that of the vacuuming effort in driving down lygus numbers. “In 2006 we’ll map the mean number of parasites against this trend of declining lygus numbers and try to see how much of the effect can be explained by parasitism.” Ultimately, Swezey hopes to convince strawberry growers to limit the use of bug vacs on their crops to critical mid season periods, and to increase the implementation of alternative controls such as trap crops combined with bio-control efforts. “I think vacuuming the whole field of crops to control lygus is counterproductive,” says Swezey. “It’s a lot of effort and I think it’s quite destructive of the beneficial insect community that could greatly help limit lygus damage in organic strawberries if it were conserved.”Interest in sustainable agriculture isn’t limited to the farm fields or grocery aisles—it’s also taking root in the classroom. Prompted in many cases by student demand, colleges and universities around the country are developing programs in organic farming, sustainable agriculture, and agroecology. Recognizing this growing interest, members of the Center for Agroecology and Sustainable Food Systems and the UC Davis College of Agricultural and Environmental Sciences and Student Farm teamed this past winter to develop the first national conference on post-secondary sustainable agriculture education. The conference drew over 140 students, faculty, staff and administrators from more than 50 national and international colleges and universities to the Asilomar Conference Center in Pacific Grove, California. Also attending were representatives from 15 state and national sustainable agriculture organizations. Conference attendees set their own agenda based on shared interests, brainstorming in more than 20 workshops on topics that ranged from how best to work across disciplines in developing curricula,vertical tower for strawberries how to develop and maintain institutional support for sustainable agriculture education and research programs, and how to incorporate student farms into education programs, to how to develop careers paths for students with interests in sustainable agriculture. According to Albie Miles, the Center’s curriculum developer and one of the conference organizers, “Many participants commented that the conference was very timely and that they had long recognized the need for a national meeting that would encourage inter-institutional exchange and collaboration between sustainable agriculture educators, researches, administrators and students.” Part of the conference’s outcome is an effort to assess the need for a national-level organization that will continue to address and promote sustainable agriculture as a field of study in higher education.
In this article we discuss the background of this effort, describe some highlights from the January conference, and offer ways to get involved in the ongoing work to develop and improve sustainable agriculture programs for post-secondary students. More information on the conference, including summaries of all the workshops, is available on the Center’s home page: www.ucsc.edu/casfs; click on the Education link and go to the Facilitating Sustainable Agriculture Conference link.Dating to the founding of the Student Garden Project in 1967 and the Agroecology Program in 1981, UC Santa Cruz has a long history of both experiential, apprenticestyle training in organic farming and gardening techniques, and more traditional academic courses in agroecology and sustainable agriculture. Building on this experience, members of UCSC’s Center for Agroecology and Sustainable Food Systems have worked with other educators from throughout California since 2002 as part of the College Farms Sustainable Agriculture Educators Working Group, with support from the Kellogg-funded California Food and Fiber Futures project. “The focus of that work was on colleges and universities that have college farms,” says Miles. “As post-secondary educators, we wanted to discuss the needs that our programs shared and to develop experiential education curricula that would incorporate hands-on work and learning on college farms into academic programs.” The California group worked on a number of projects together, convened several meetings each year, and held workshops for the last three years at the annual Ecological Farming Conference. Realizing the need for an effort that served the broader sustainable agriculture education community, the California educators proposed the idea of convening a national, multi-day sustainable agriculture education conference. “In 2005 we conducted a survey of selected individuals and US institutions involved in sustainable agriculture education to assess interest in a national conference as well as to solicit input on the conference’s content,” says Miles. “The great majority of respondents from our initial survey strongly supported the idea of a national conference.” Miles, along with Mark Van Horn, director of the UC Davis Student Farm, and Damian Parr, graduate student in agricultural education at UC Davis, formed the conference steering committee. Both educators and students provided feedback on what issues were of greatest interest and concern . Colleagues at the Center provided the impetus for the use of Open Space Technology for structuring the event such that the content of the conference was determined by the needs and interests of the participants. Both graduate and undergraduate students played a significant role in the conference. As one of the primary conference organizers, Parr stressed the importance of developing the conference as a progressive “educational event” with a participatory, inclusive curriculum. Central to this principle was assuring students’ authorship in developing the conference program and outcomes. Parr, a member of the Center’s 1991 Apprentice class and a UCSC Environmental Studies/Agroecology graduate in 2000, notes that, “We facilitated a social learning process wherein administrative, faculty, and student cultures increased awareness of their respective needs and interests. Ultimately, the goal was to democratize knowledge and practice responsibility for what and how we learn about sustainable agriculture.” With the ongoing efforts to develop a more sustainable campus food system at UCSC , members of the Center’s social issues research group are interested in assessing student, staff, and faculty attitudes, concerns and support for a variety of food system issues.