Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 4/1/2008
Publication Date: 8/5/2008
Citation: Porter, L., Coffman, V.A. 2008. Assessment of organic seed treatments to manage seed and root rot on peas, 2007. Plant Disease Management Reports (online). Report 2:V153. DOI:10.1094/PDMR02. The American Phytopathological Society, St. Paul, MN. Interpretive Summary: Seed and root rotting pathogens such as Pythium species are considered to be major soilborne diseases affecting pea seed and roots in the Pacific Northwest. Seeding rates used by organic pea growers are often twice the amount of that used for commercial production due to poor control of seed rotting pathogens in the soil. Many organic pea growers do not use seed treatments on their pea seed and feel that currently available seed treatments are not providing sufficient protection from seed rot. There are several products that have been certified by the Organic Materials Review Institute (OMRI) for organic food production that have not been tested as potential seed treatments, or they have been previously tested, but further information on their efficacy is needed. These products could potentially reduce the risk of poor stand development due to seed and root rotting pathogens and improve organic pea yields. The present research tested twenty-two potential organic seed treatments in a commercial organic field and identified that Nordox and Biomin Copper significantly increased plant emergence and dry root weight, respectively, compared to the non-treated control. In addition, the biological seed treatment, Kodiak, significantly reduced the root rot severity compared to the non-treated control. Although eleven of the seed treatments had yields that were numerically greater than the non-treated control, none of the seed treatments significantly (P < 0.05) improved yields above that of the non-treated control. The Nordox product provides a great potential organic seed treatment to improve plant emergence. Additional nutritional and biocidal studies need to be conducted to identify the reason for the improved emergence. Currently, Nordox can only be used in organic pea production if there is a documented copper deficiency in the crop soil.
Technical Abstract: Five biological and seventeen non-biological seed treatment, were evaluated in a commercial organic field (silt loam soil) in Moses Lake, WA to manage seed and root rot of processed peas. The soil from the field site had a mean of 456 colonies of Pythium per gram of soil. Emergence of seed treated with Nordox was significantly greater than (P < 0.05) that of the non-treated control (NTC), and emergence of seed treated with Rhizopro and Fulmag + zinc sulfate significantly decreased emergence compared to the NTC. There were no seed treatments that significantly increased plant height greater than the NTC. Root disease severity was significantly less for seed treated with Biomin Calcium and Kodiak than for seed of the NTC. Root disease severity was significantly greater for the NTC than for the Biolink surfactant, soluable corn syrup, molasses, Actinovate and Fulmag. There were no seed treatments that significantly increased the foliar dry weight above that of the NTC, but Rhizopro, Nordox, Fulmag, and shrimp significantly decreased the foliar dry weight compared to the NTC. The dry root weight of seed treated with Biomin Copper was the only seed treatment that significantly increased dry root weight above that of the NTC. Seed treated with Humax + zinc sulfate was the only product that significantly decreased dry root weight compared to the NTC. None of the treatments significantly increased yield above that of the NTC, however, Fulmag + zinc sulfate significantly decreased yield compared to the NTC. None of the treatments significantly increased tenderometer readings compared to the NTC, and Rhizopro was the only treatment that significantly decreased tenderometer readings compared to the NTC. Among the seed treatments tested, Nordox appears to be the most effective organic seed treatment that would improve emergence of seed in organic pea production. It is not known if this product is improving emergence due to better plant nutrition or if it is a biocide to seed and root rotting bacteria or fungi. Nordox can only be used in organic production if there is a documented copper deficiency in the soil.