Current Research in Farming Systems and Agroecology Science
Anaerobic Soil Disinfestation to Control Verticillium
Finding a non-fumigant alternative to the soil fumigant methyl bromide has been identified as a top priority by the California Strawberry Commission, and by growers who are facing the phase out of this ozone-depleting pesticide. However, most current state and federal research is focused on alternative fumigants rather than non-fumigant techniques to control soil diseases, weed seeds, and harmful nematodes.
Preliminary research conducted at the UCSC Farm has shown promising results with an alternative approach that 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 the past several seasons at the Farm and has been shown to control the soil pathogen Verticillium dahliae, a major diseases of strawberries.
A study funded by a grant from the US Department of Agriculture has 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.
Muramoto reports promising results from the 2008 work in Florida in suppressing weeds with the ASD technique, as well as in California in reducing V. dahliae in soils with high clay content. Further studies will include determining the optimum irrigation rate for a given soil type in California in order to use ASD effectively.
CASFS participants: Jim Leap, Joji Muramato, Carol Shennan. Cooperators: Mark Bolda, Karen Klonsky, Steve Koike, UC Cooperative Extension. Funding: U.S. Department of Agriculture. Related publications – Brown, M. 2007. Study on methyl bromide alternatives expands with USDA funding. The Cultivar 25 (1,2): 18.
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. Brown, M. 2009. Field trials of methyl bromide alternative show promise. The Cultivar 27 (1): 14.
Blueberry Variety Trial at the UCSC Farm
A variety trial examining the performance of 15 varieties of blueberries grown under organic conditions is underway at the CASFS Farm on the UCSC campus. Planted in January 2004, the ongoing trial is designed to provide organic growers with information on appropriate varieties for Central Coast growing conditions.
CASFS participants: Jim Leap, Liz Milazzo Cooperators: Aziz Baaumeur and Mark Bolda, UC Cooperative Extension Related publication – Brown, M. 2007. Blueberry variety trial at UCSC Farm bears promising fruit. The Cultivar 25 (1,2): 5–6.
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 Lygus and evaluates potential host plants. as well as examining parasitism distribution patterns. These efforts will help establish a unique systems-management approach to lygus bug control in organic strawberries that offers physical suppression (trap crop vacuuming), integrated parasitism, and resources for sustained biological control.
CASFS participants: Janet Bryer, Diego Nieto, Sean Swezey Cooperators: Charles Picket, CDFA Biological Control Program; Pacific Gold Farm Funding: Organic Farming Research Foundation Related publication - 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.
Lygus hesperus Control in Strawberries
The lygus bug, Lygus hesperus, is a major pest of strawberries on California’s Central Coast. Center researchers have spent several years developing an effective “trap crop” system and parasitoid introductions for this pest. Early-season plantings of radish and late-season plantings of alfalfa are planted at the borders of the fields, creating a continuous bloom throughout the cropping season, and attracting lygus away from the strawberry crop. Researchers currently monitor the effects of a weekly vacuuming program to see whether it controls lygus populations both in the trap crops and the strawberry crops. They also monitor for lygus damage in strawberries adjacent to the trap crops as well as those farther from the field edge.
A 2009 grant from the U.S. Department of Agriculture's "Crops at Risk" program will fund the efforts of Center researchers Sean Swezey, Diego Nieto, and Janet Bryer to better understand the springtime movement of lygus bugs, using an innovative marking technique for studying the movement of pests and predators within and beyond crop fields.
The project focuses on the techniques of managing alfalfa trap crops to intercept lygus as they migrate from areas surrounding strawberry fields in the spring. According to the researchers, alfalfa trap cropping’s greatest potential as a lygus management tool may be during this period, when the issue of plant host preference is most relevant.
CASFS participants: Janet Bryer, Diego Nieto, Sean Swezey Cooperator: Pacific Gold Farms Funding: USDA Western Sustainable Agriculture Research and Education program, USDA Pest Management Alternatives Program, USDA Crops at Risk Program.Related publications – 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. 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. 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.
