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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #303024
Title: A mineral seed coating for control of seedling diseases of alfalfa suitable for organic production systems

Author
item Samac, Deborah - Debby
item SCHRABER, SAMUEL - University Of Minnesota
item BARCLAY, STUART - Summit Seed, Inc

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2014
Publication Date: 5/29/2015
Citation: Samac, D.A., Schraber, S., Barclay, S. 2015. A mineral seed coating for control of seedling diseases of alfalfa suitable for organic production systems. Plant Disease. 99(5):614-620.

Interpretive Summary: Establishing alfalfa fields can be challenging because alfalfa seeds and seedlings are vulnerable to pathogens in the soil that kill plants or cause damage that decreases plant productivity and winter survival. The majority of alfalfa seed is treated commercially with the fungicide Apron XL to provide protection against disease. However, Apron XL does not have activity against the causal agent of Aphanomyces root rot, which is a highly destructive disease, and Apron XL-treated seed cannot be used in organic production systems. Effective seed treatments that meet the organic standards are needed to expand production of organic alfalfa for support of organic dairy and animal production systems. A novel mineral seed treatment using aluminosilicate (natural zeolite) was tested as an alternative alfalfa seed treatment. Zeolite is allowed under the National Organic Plan (NOP) Rule 205.203(d)(2). In growth chamber assays, the mineral seed treatment gave significantly greater control of three major seedling diseases of alfalfa, including Aphanomyces root rot, than the Apron XL seed treatment. The mineral seed treatment resulted in a similar or greater percentage of protected plants than the Apron XL treatment in assays with field soils with a range of disease pressure. The mineral treatment had no effect on symbiotic bacteria needed for nitrogen fixation. These experiments indicate that the zeolite mineral seed treatment is a promising means of controlling seedling diseases in conventional and organic alfalfa production systems.

Technical Abstract: Most alfalfa seed is treated with the systemic fungicide mefenoxam (Apron XL) for control of soilborne seedling diseases. However, Apron XL does not have activity against Aphanomyces euteiches, the causal agent of Aphanomyces root rot (ARR), which is an important component of the alfalfa root rot complex. Moreover, Apron XL-treated seed cannot be used in organic production systems. A novel mineral seed treatment using aluminosilicate (natural zeolite) was tested as an alternative alfalfa seed treatment. Zeolite is allowed under the National Organic Plan (NOP) Rule 205.203(d)(2). In growth chamber assays, the mineral seed treatment gave significantly greater control of Phytophthora root rot and ARR than the Apron XL seed treatment. The mineral treatment also provided greater protection than Apron XL against Pythium ultimum and P. paroecandrum in in vitro assays for seed rot and damping off. The mineral seed treatment resulted in a similar or greater percentage of protected plants than the Apron XL treatment in assays with naturally infested field soils with a range of disease pressure. The mineral treatment had no effect on in vitro growth of Sinorhizobium meliloti and nodulation of roots from mineral-treated seed and control seeds was similar. These experiments indicate that the zeolite mineral seed treatment is a promising means of controlling seedling diseases in alfalfa production systems.