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A mineral seed coating for control of seedling diseases of alfalfa suitable for organic production systems
- Deborah A. Samac, Samuel Schraber, Stuart Barclay
- Plant disease 2015 v.99 no.5 pp. 614-620
- Pythium paroecandrum, seedlings, Aphanomyces euteiches, alfalfa, microbial growth, nodulation, roots, damping off, seed dressings, organic production, crop production, seeds, Phytophthora, coatings, disease control, soil, zeolites, in vitro studies, Pythium ultimum, Medicago sativa, Ensifer meliloti, root rot, growth chambers
- 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.