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Development of organic pea seed treatments with efficacy against Pythium seed rot

Lyndon Porter: USDA-ARS

<div>In 2016, organic peas were grown on 1,347 ha in the state of Washington and on 3,726 ha nationally. A major limitation to organic pea production is seed rot and seedling damping off caused by <em>Pythium</em> spp., particularly <em>Pythium ultimum</em>. Twenty-six organic pea seed treatments were evaluated in two field trials in 2017 to assess the efficacy of these products in improving multiple growth parameters including seedling emergence and yield. Nordox 75 WG (a.i. 83.9% cuprous oxide), and GEX170008 (a.i. not disclosed), a commercial organic seed treatment developed by Germains Seed Technology, significantly (<em>P</em> ≤ 0.05) increased emergence compared to water-treated seed by 23.3 and 57.9% in field 1, respectively, and 27.4 and 37.9% in field 2, respectively. Nordox and GEX170008 increased yields compared to the water control by 40.6 and 77.9% in field 1, respectively, and 23.0 and 5.1% in field 2, respectively. The <em>Pythium</em> disease pressure was not as severe in field 2 as in field 1. Despite these increases in yield, only the 77.9% increase in field 1 was significantly (<em>P</em> ≤ 0.05) greater than the water-treated control. GEX170008 is one of the first non-biological organic seed treatment to provide significant protection against Pythium seed rot resulting in more uniform emergence and improved yields in pea. Currently Nordox 75 WG and GEX170008 are not registered for organic use on peas as seed treatments.</div>