Evaluation of seed treatments for organic vegetable production in the Pacific Northwest

CSANR Project 045

Status: Complete

Project Summary

This study addresses management of damping-off in organic vegetables in central Washington, using pea as an early season, model crop. The disease is being examined under low soil temperature and high soil moisture conditions of early spring in the Columbia Basin, when damping-off is most severe. PhD student, Ana Vida Alcala, spent 2009 and spring 2010 in Pullman, completing courses. In 2009, soil samples were collected from 37 organic fields in the Basin. Alcala obtained >300 Pythium isolates from the soils, which she identified to species using DNA sequencing. For each of 19 Pythium species, up to 9 isolates from across the Basin were evaluated in growth chamber trials for pathogenicity on pea in cool, moist, organic soil from a grower-cooperator’s field. Isolates of 11 of the 19 species were pathogenic on pea. In 2011, organic seed/drench treatments (microbial and non-microbial) were evaluated in four field trials: 15 treatments in each of 2 trials in grower-cooperator, organic pea crops in the Basin; and 20 treatments in inoculated pea and sweet corn trials at the WSU Mount Vernon NWREC. The more promising treatments were evaluated again in 2012 applied to both primed and non-primed seed in each of two field trials. In addition, the use of primed seed that was dried with biochar instead of dry air and then treated with Nordox (organic copper), showed potential for improving pea emergence, height, and yields in one of two grower-cooperator trials in the Columbia Basin. Results from the 2011 and 2012 field trials were presented at the Pacific Northwest Vegetable Assoc. Convention & Trade Show in November of 2011 and 2012. The 2011 trial results also were published in Plant Disease Management Reports (Vol. 6:ST011 and ST012), and the 2012 trial results were submitted in Dec. 2012 for publication in Vol. 7. Finally, Alcala is evaluating the potential use of electrolyte leakage measurement of pea seed lots as a predictor of the risk of damping-off at different levels of inoculum pressure of Pythium spp. in organic soil, which growers may be able to use in combination with soil assays for this pathogen to select appropriate seed lots for reduced risk of damping-off. The growth chamber trials completed in 2012 on this aspect of the project are very promising. Alcala anticipates completing her PhD by May 2013.

Annual Entries

2008

Principal Investigator: Lindsey du Toit
Additional Investigators: T. Paulitz
Lyndon Porter
Graduate Student: Ana Vida Alcala
Progress Report: http://csanr.wsu.edu/wp-content/uploads/2008/06/ProgReport-du-Toit-Seeds-2008.pdf
Grant Amount: $40,000

2009

Principal Investigator: Lindsey du Toit
Additional Investigators: T. Paulitz
Lyndon Porter
Graduate Student: Ana Vida Alcala
Progress Report: http://csanr.wsu.edu/wp-content/uploads/2008/06/DuToit-FY09-progress-Seed-Treat.pdf
Grant Amount: $40,000

2010

Principal Investigator: Lindsey du Toit
Additional Investigators: T. Paulitz
Lyndon Porter
Graduate Student: Ana Vida Alcala
Progress Report: http://www.tfrec.wsu.edu/pdfs/P2271.pdf
Grant Amount: $78,677

2011

Principal Investigator: Lindsey du Toit
Additional Investigators: T. Paulitz
Lyndon Porter
Graduate Student: Ana Vida Alcala
Progress Report: http://www.tfrec.wsu.edu/pdfs/P2274.pdf
Grant Amount: $35,306

Publications

Alcala, A.C., and du Toit, L.J. 2009. Management of damping-off in organic vegetable crops in the Pacific Northwest. Sustaining the Pacific Northwest 7(4):5-7. http://csanr.wsu.edu/publications/SPNW/SPNW-v7-n4.pdf.

;Alcala, A.C., Derie, M.L., Holmes, B., Gatch, E.W., Porter, L.D., Coffman, G., and du Toit, L.J. 2012. Evaluation of organic seed and drench treatments for controlling damping-off in pea and sweet corn in Mount Vernon, WA, 2011. Plant Disease Management Reports 6:ST011.

Alcala, A.C., Derie, M.L., Holmes, B., Gatch, E.W., Porter, L.D., Coffman, G., and du Toit, L.J. 2012. Evaluation of organic seed and drench treatments for controlling damping-off in organic pea crops in the semi-arid Columbia Basin of Oregon and Washington, 2011. Plant Disease Management Reports 6:ST012.

Alcala, A.C., du Toit, L.J., Derie, M.L., Holmes, B., Coffman, G., Gatch, E.W., and Porter, L.D. 201_. Evaluation of priming and Nordox seed treatment for controlling damping-off in organic pea crops in central Washington, 2012. Plant Disease Management Reports 7: submitted 10 Dec. 2012, in review.

Alcala, A.C., Porter, L.D., Derie, M.L., Holmes, B., Coffman, G., and du Toit, L.J. 201_. Evaluation of seed treatments and priming for controlling damping-off in organic pea crops in the semi-arid Columbia Basin and maritime Skagit Valley of Washington, 2012. Plant Disease Management Reports 7: submitted 10 Dec. 2012, in review.

Lindsey du Toit’s Vegetable Seed Pathology team website at: http://www.mountvernon.wsu.edu/VSP/VSP_team.htm#avi

WSU CAHNRS. http://news.cahnrs.wsu.edu/2012/03/07/fighting-damping-off-small-bites-cranberry-pioneers-upcoming-events/

Alcala, A. C., Paulitz, T. C., Porter, L. D., and du Toit, L. J. 2011. Profile of Pythium spp. in certified organic fields for vegetable production in central Washington. APS Annual Meeting, Honolulu, Hawaii, 6-10 August 2011. Phytopathology 101:S4.

Alcala, A.C., Derie, M.L., Holmes, B., Gatch, E.W., Porter, L.D., Coffman, G., and du Toit, L.J. 2012. Evaluation of organic seed and drench treatments for damping-off in organic pea crops in the semi-arid Columbia Basin, Oregon and Washington, 2011. Plant Disease Management Reports 6: submitted Dec. 2011.

Alcala, A.C., Derie, M.L., Holmes, B., Gatch, E.W., Porter, L.D., Coffman, G., and du Toit, L.J. 2012. Evaluation of organic seed and drench treatments for damping-off in pea and sweet corn in Mount Vernon, WA, 2011. Plant Disease Management Reports 6: submitted Dec. 2011.

Alcala presented a summary of this project at the WSU Mount Vernon NWREC Graduate Student Sustainability Symposium on 27 October 2011 at Mount Vernon, WA, attended by graduate students from WSU, Western Washington University, and the University of Washington.

Impacts and Outcomes

Research is still in progress as a PhD project for Ana Vida Alcala. Student started on this project in January 2009.;It is too soon to assess this, but grower interviews in 2009 identified key research needs for damping-off in organic vegetable crops in the PNW, and the fact that most growers of organic produce do not currently use seed treatments because of inconsistency in performance when they have evaluated such products. Some stakeholders indicated a willingness to pay as much as $100 to $150/acre for a seed treatment that consistently will help manage damping-off, by increasing stand/emergence by ~30%, because they currently overseed about this amount to compensate for losses to damping-off. Alcala’s work has demonstrated a diversity of Pythium species associated with certified organic fields in the semi-arid region of the Columbia Basin, but strains of some species appear not to be pathogenic on pea during cool, wet spring conditions. Three to four of the species Alcala isolated appear to have predominantly pathogenic strains on pea under these conditions, so management practices for damping-off in organic pea crops should be effective against all of these potentially pathogenic species. The field trials demnstrated that a majority of products currently registered for use in organic pea crops in WA State were not effective at reducing damping-off under the conditions of these trials, both in central WA and northwestern WA. Although, seed priming, HeadsUp, Acadian, Nordox, Prestop, and Naturall II (at least in the sweet corn trial) treatments showed some potential in some trials, the performance of these products was not consistent across three of the four trials in which significant damping-off was observed. This concurs with growers’ observations, and demonstrates the importance of evaluating these treatments again in 2012 to assess consistency in efficacy.