Current Research in Farming Systems and Agroecological Science


    Anaerobic Soil Disinfestation (ASD) to Control Verticillium and Weed Seed Germination

  • ASD was developed in the Netherlands and Japan independently and through the work of UCSC researchers and their partners is being optimized for California strawberries. The first successful ASD trial in the US was conducted at the CASFS farm to control Verticillium wilt in organic strawberries in 2003. In the 2014-15 season, over 1,000 acres of strawberries and cane berries in California, of which 80% are organic fields and 20% conventional (buffer zone), are being produced using ASD.

    ASD starves pathogens and weeds of oxygen. Researchers introduce a carbon source such as chopped cover crops, wheat bran, or molasses to the strawberry bed, then irrigate and tarp the beds to create temporary anaerobic conditions. This technique, known as anaerobic soil disinfestation (ASD), has been tested for a number of seasons at the CASFS/UCSC Farm and has been shown to control the soil pathogen Verticillium dahliae, a major diseases of strawberries.

    Several studies funded by grants from the US Department of Agriculture and the California Strawberry Commission have expanded this initial work to examine the efficacy of various carbon sources, irrigation techniques, tarp types, and tarping periods to create sufficient anaerobic conditions to control weed seed germination and V. dahliae. Research is underway at the UCSC Farm and at cooperator farms in the Central Coast region focusing on understanding the mechanisms of how ASD works, and how to optimize its use and effectiveness in terms of timing, soil temperature, and carbon source used for specific target pathogens. A 2017 grant of $2.5 million from the USDA will expand this effort to locations in Florida, North Carolina, and Tennessee to help fine tune the ASD technique in different climate zones and crops.

    Read about the 2017 USDA Grant to expand ASD research

    Learn more about ASD research on the Shennan Lab Group's website.

    Watch a video about the CalCORE project to improve organic vegetable and strawberry rotation systems in the Monterey Bay region. 

    CASFS/UCSC participants: Joji Muramato, Carol Shennan, Darryl Wong, Graeme Baird, Marguerite Zavatta. Cooperators: Mark Bolda, Karen Klonsky, Steve Koike, UC Cooperative Extension, Farm Fuel, Inc. Funding: U.S. Department of Agriculture.

    Selected related publications – 
    • Butler, D.M., E.N. Rosskoph, N. Kokalis-Burelle, J. MuramotoC. Shennan, S. Koike, M. Bolda and O. Daugovish. 2009. Impact of Anaerobic Soil Disinfestation on introduced inoculum of Phytophthora capsici and Verticillium dahliaePhytopathology 99:S18
    • Coombs, Amy. 2013. Growing berries without bromideSanta Cruz Good Times.
    • Fennimore, S., et al. 2013. TIF film, substrates and nonfumigant soil disinfestation maintain fruit yields. California Agriculture 67:3, 139–146.
    • Lasnier, G. 2011 UCSC wins $2.6 million grant for orgnanic farming research. UCSC News.
    J. Muramoto, J., C. Shennan, G. Baird, M. Zavatta, S. T. Koike, O. Daugovish, M. P. Bolda, S. K. Dara, K. Klonsky, and M. Mazzola. 2014. Optimizing anaerobic soil disinfestation for California strawberries. Acta Horticulturae 1044:215-220.
    • Shennan, C., J. Muramoto, M. Mazzola, D. Butler, E. Rosskoph, N. Kokalis-Burelle, K. Momma, Y. Kobara, J. Lamers. 2014. Anaerobic soil disinfestation for soil borne disease control in strawberry and vegetable systems: Current knowledge and future directions. Acta Horticulturae 1044:165-175.
    • Shennan, C., Muramoto, J., Koike, S., Bolda, M., Daugovish, O., Mochizuki, M., Rosskopf, E., Kokalis-Burelle, N., and Butler, D. 2010 Optimizing anaerobic soil disinfestation for strawberry production in California. Proceedings of the Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, Orlando, FL. p 23.1 - 23.4
    • Shennan, C., J. Muramoto, M. Bolda, S. T. Koike, O. Daugovish, E. Rosskopf, N. Kokalis-Burelle, and K. Klonsky. 2007. Optimizing anaerobic soil disinfestation: an alternative to soil fumigation. Page 40-1 to 40-4 in Proceedings, Annual International Research Conference on Methyl Bromide Alternatives and Emission Reduction, San Diego, CA.
    • Shennan C., J. Muramoto J., G. Baird, et al. 2011. Anaerobic soil disinfestation: California. In: Proceedings, Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, Oct. 31–Nov. 2, 2011. San Diego, CA. Abstr. 44.


  • Cabbage Maggot Management in Cole Crops

  • California Brassica growers lack cabbage maggot monitoring techniques and economic threshold guidelines, both critical components of integrated pest management.  Consequently, growers often employ sub-optimal organophosphate applications that lack precision and can promote insecticide overuse. A series of IPM tools, including effective monitoring technologies, economic damage thresholds and alternative chemical strategies will also be developed to help growers implement IPM for control of cabbage maggot in broccoli and Brussels sprouts production.

    CASFS/UCSC participants: Deborah Letourneau, Carol Shennan, Janet Bryer, Diego Nieto Cooperators: Lakeside Organic Gardens; Funding: California Department of Pesticide Regulation


  • CDFA 2014 Specialty Crop Block Grant Program—Specialty Crop Farmer Training and Toolkit for a Sustainable Future

  • This project builds on over 40 years of organic specialty crop production and training of beginning farmers at the 30 acre farm and three acre market garden of the Center for Agroecology & Sustainable Food Systems (CASFS) at the University of California, Santa Cruz (UCSC). It also builds on a CASFS-led regional collaboration for beginning farmer training and the CASFS online curriculum for agriculture educators. This new project will produce a specialty crop Toolkit featuring eight to ten Grower Guides in English and Spanish on specific crops grown using organic and sustainable production practices. These crops will be demonstrated at the CASFS farm, with distinct blocks of mixed vegetables and cut flowers providing data for publications covering varietal choices, production practices, and economic analysis. Specialty crop classes, field days, and mentoring sessions using these materials and demonstration blocks will be delivered to over 250 new and beginning small-scale farmers during the project. 

    See the Grower Guides series developed as part of this specialty crops grant.

    CASFS/UCSC participants: Christof Bernau, Martha Brown, Kirstin Comerchero, Sky DeMuro, Orin Martin, Eliza Milio, Jan Perez, Darryl Wong Funding: California Department of Food and Agriculture Specialty Crops Block Grant Program


  • Collection, Release and Establishment of Peristenus digoneutis, a European Lygus Bug Parasitoid, on the California Central Coast

  • Lygus bugs (Lygus hesperus) are a key pest of strawberries on the California central coast. Two European parasitoids, Peristenus relictus and Peristenus digoneutis, were released in Santa Cruz and Monterey Counties as part of a California Strawberry Commission-funded project to reduce lygus bug populations. P. relictus has since become established in California and has contributed to lygus bug reductions in strawberries. P. digoneutis did not become established; this was likely attributable to a poor climatic match between where it was collected and released.

    This project aims to improve lygus bug control through the collection, release and establishment of a new P. digoneutis population that is best-suited to the strawberry-growing regions of central California. Based on this parasitoid’s performance in Europe and the northeastern United States, we anticipate that its establishment will benefit California strawberry growers by further diminishing lygus bug populations.    

    CASFS/UCSC participants: Janet Bryer, Diego Nieto, Carol Shennan. Cooperators: Kim Hoelmer, USDA; Charles Pickett, CDFA; Michael Seagraves, Driscoll's Berries; Tom Dorsey, New Jersey Dept. of Agriculture. Funding: 


  • Effects of Fertility on Aphid Density in Broccoli and Cauliflower Crops

  • This project examines the effect of three treatments (zero, medium, and high) of organic nitrogen fertilizer on aphid density in broccoli and cauliflower crops. Cabbage aphid and DBM numbers and harvest rates (floret size, % contamination) will be compared between treatments 1a, 2a and 4a (Table 1) representing a range of N input levels. 

    On half of the treatment replicates Entrust, a spinosad-based organically-compliant insecticide, will be applied to eliminate syrphid larvae (Smith et al. 2008), in order to clarify the effect of fertility on aphid densities.  This method of syrphid exclusion will also allow us to distinguish the efficacy of syrphid predation relative to aphid abundance and harvest rates.  

    CASFS/UCSC participants: Carol Shennan, Sean Swezey Funding: USDA OREI 


  • Implementing Anaerobic Soil Disinfestation for Soilborne Disease Control in Strawberries and Apple Nurseries

  • Anaerobic soil disinfestation (ASD) controls soilborne disease by acid fermentation process through anaerobic decomposition of incorporated carbon sources (see above). Rice bran is the most typical carbon source for ASD in California. However the cost of rice bran is increasing and the use of cover crop as a carbon source may be able to reduce the cost and the carbon footprint of the practice.

    This 3-year grant supports an ongoing pilot study iat the CASFS/UCSC Farm comparing Sudan grass or wheat as cover crop, each cover crop plus reduced rate of rice bran, rice bran only, and un-treated check. Soil N dynamics and strawberry yield are being monitored.

    CASFS/UCSC participants: Carol Shennan, Joji Muramoto

    Funding Source: US Department of Agriculture Methyl Bromide Transition Program


  • Insect Biodiversity in Santa Cruz Area Urban Gardens: Baseline Date and an Opportunity for Undergraduate Research

  • Urbanization threatens biodiversity, but urban gardens may provide an oasis for biodiversity while also  providing social and economic benefits. Anecdotal and empirical evidence suggests that urban gardens provide habitat and improve air quality and protect nearby residents from flooding. Gardens can increase multiculturalism, cross-cultural exchange, and provide spaces for meetings and recreational activities.  Gardens have been linked to increased health of residents and garden produce can sometimes be sold, contributing to local economies. Insects are diverse and abundant organisms.

    In agroecosystems, including urban gardens, insects provide important services, such as pollination and pest control. However, few studies have examined the drivers of insect biodiversity in urban gardens, and the implications of this diversity for pollination and pest control services.

    This project examines insect biodiversity in 19 urban gardens in the Central Coast region, including the handworked gardens at the UCSC Farm and UCSC’s Alan Chadwick Garden. Garden study sites capture a range of landscape diversity (e.g. forest, farmland, pasture, or urban sprawl), a range of economic status, and a large degree of cultural diversity. Insect sampling focuses on 5 groups including one group of pollinators (bees), and four groups of organisms that provide pest control services (ants, spiders, wasps, and ground beetles). UCSC undergraduates are assisting with sampling insects and plants, and students with interest in Geographic Information Systems (GIS) are examining the landscapes surrounding each study site.

    Project goals include collecting preliminary data on insect biodiversity in gardens in communities that differ in surrounding landscape, economic status, and ethnic backgrounds; laying the groundwork for a research program investigating biodiversity and ecosystem services in urban habitats; and providing a research umbrella under which UCSC undergraduates can complete senior exit internships and theses.

    CASFS/UCSC participants: Stacy Philpott, UCSC Research Specialist Peter Bichier, UCSC undergraduate students Simone Albuquerque, Stephanie Coronado, Michelle Otoshi, Robyn Quistberg, and Casey Wing. Cooperators: City of San Jose Community Gardens, City of Santa Cruz City Gardens, Salinas Chinatown Garden, ME Earth, Our Green Thumb at Monterey Institute of International Studies, Seaside Giving Garden, Mi Jardin Verde, Homeless Garden Project, Live Oak Grange, Aptos Community Garden, Salinas Community Garden, The Forge at Santa Clara University. Funding: UCSC New Faculty Research Grant.


  • Integrating Biological Control with Trap Crop Management in California Organic Strawberries

  • This project integrates an imported biological control agent into managed alfalfa trap crops in order to improve control of a key pest, the lygus bug (Lygus hesperus) in organic strawberries. By incorporating the selective endoparasitoid Peristenus relictus, which is a nymphal parasitoid of the lygus bug, into a managed alfalfa trap crop system, a more balanced systems-management approach to control of a key pest is being achieved.

    This study examines the effectiveness of P. relictus at parasitizing L. hesperus. Parasitism distribution patterns are being examined, with an emphasis on alfalfa’s effects on parasitism in associated strawberries. Also of interest is describing the ability of this parasitoid to persist within a managed trap-cropping system, where alfalfa is routinely treated with a tractor-mounted vaccum. These efforts will help establish a management approach to lygus bug control in organic strawberries that integrates both physical suppression (trap crop vacuuming) and biological control.  

    CASFS/UCSC participants: Janet Bryer, Diego Nieto, Sean Swezey Cooperators: Charles Picket, CDFA Biological Control Program; Pacific Gold Farm Funding: USDA Organic Agriculture Research and Extension Initiative (OREI)

    Related publications and presentations -
    • Brown, M. 2006. Center researchers find pest control help for Central Coast organic strawberries. The Cultivar 24 (1): 5–6.
    • Pickett, C. H., S. L. Swezey, D. J. Nieto, J. A. Bryer, M. Erlandson, H. Goulet, and M. D. Schwartz. 2009. Colonization and establishment of Peristenus relictus (Hymenoptera: Braconidae) for control of Lygus spp. (Hemiptera: Miridae) in strawberries on the Central California Coast. Biological Control 49: 27-37.
    • Pickett, C. H., Nieto, D. J., Bryer, J. A., Swezey, S. L., Stadtherr, M., Wisheropp, D., Erlandson, M. & M. Pitcairn. 2013. Post-release dispersal of the introduced lygus bug parasitoid Peristenus relictus in California. Biocontrol Science and Technology 23: 861-871.
    • Nieto, D. 2013. Trap cropping in organic strawberries to manage lygus bugs in California. eOrganic Webinar.


  • Lygus hesperus Control in Strawberries

  • The lygus bug, Lygus hesperus, is a key pest of strawberries on California’s Central Coast. Center researchers have spent a number of years developing an effective “trap crop” system for this pest. Rows of alfalfa are inter-planted in strawberry fields to attract lygus bugs away from the strawberry crop. A tractor-mounted vacuum is then used weekly to remove this pest from alfalfa. Lygus bug-induced strawberry damage is monitored to document yield improvements associated with trap cropping.


    One important component of pest management relates to movement into and within this system. By utilizing protein-marking techniques, preferential springtime lygus bug adult immigration into alfalfa trap crops (relative to adjacent strawberry rows) can be verified. Alfalfa’s mid-summer retention of lygus bugs, also verified through these marking techniques, is useful in describing pest behavior in the context of plant host preference.   

    CASFS/UCSC participants: Sean Swezey, Janet Bryer, Diego Nieto, Carol Shennan. Cooperators: James Hagler and Scott Machtley, USDA-ARS, Pacific Gold Farms Funding: USDA Organic Agriculture Research and Extension Initiative (OREI)

    Related publications and presentations –
    • Brown, M. 2002. USDA grant funds Lygus study. The Cultivar 20 (1): 11.
    • Brown, M. 2007. Strawberry pest control research garners federal funding. The Cultivar 25 (1,2): 17. 
    • Brown, M. 2009. New tracking method helps researchers design pest control strategies. The Cultivar 27 (1): 1-2, 22. Brown, M. 2009. New "crops at risk" grant funds lygus control efforts. The Cultivar 27 (1): 14.
    • Nieto, D. 2013. Trap cropping in organic strawberries to manage lygus bugs in California. eOrganic Webinar.
    • Swezey, S. L., D. Nieto, and J. Bryer. 2007. Control of western tarnished plant bug, Lygus hesperus, Knight (Hemiptera: Miridae) in California organic strawberries using alfalfa trap crops and tractor-mounted vacuums. Environmental Entomology 36(6): 1457–1465. 
    • Swezey, S. L., Nieto, D. J., Hagler, J. R., Pickett, C. H., Bryer, J. A. and S. A. Machtley. 2013. Dispersion, distribution and movement of Lygus spp.(Hemiptera: Miridae) in trap-cropped organic strawberries. Environmental Entomology 42: 770-778.


  • Natural Enemies in the Garden

  • In urban agroecosystems, ecological functions such as pest predation by insect natural enemies result in ecosystem services that increase crop life and production. This study examines drivers of pest predation services in urban gardens and correlate services with garden features. Observational and manipulative research on the relationship between aphid pests and ladybeetle predators are used to ask: 1) what local or landscape characteristics of gardens correlate with abundance and taxonomic and functional diversity of predators in urban gardens? 2) What features of gardens or predator communities enhance predation services? 3) What local pest management strategies do practitioners employ in each respective urban garden?

    This research aims to contribute to understanding impacts of community biodiversity and composition on ecosystem services, and of potential ecological mechanisms and social practices enhancing services in urban agroecosystems.

    CASFS/UCSC Participants: Monika Egerer, Stacy Philpott  Funding : Heller Agroecology Graduate Student Research Grant

See Also