Seed Treatments for Control of the Tall Fescue Endophyte Acremonium coenophialum. M. J. Williams, Department of Botany, Plant Pathology, and Microbiology, Alabama Agricultural Experiment Station, Auburn University, AL 36849. P. A. Backman, E. M. Clark, and J. F. White, Department of Botany, Plant Pathology, and Microbiology, Alabama Agricultural Experiment Station, Auburn University, AL 36849. Plant Dis. 68:49-52. Accepted for publication 25 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-49.

The fungal endophyte Acremonium coenophialum has been implicated in fescue toxicosis, an animal disorder common on the 14 × 10⁶ ha of tall fescue (Festuca arundinacea) grown in the United States. Nonchemical and chemical seed treatments were evaluated for their ability to eradicate the endophyte from infected fescue seed, the only known means of endophyte transmission. On-farm storage for about 12 mo or a hot-water treatment (presoak 6 hr at 5 C plus 20 min at 60 C) eradicated the endophyte in the seed tested. The sterol inhibitor triadimenol and its analog triadimefon were the most effective fungicides at the rates tested. Either chemical at 4.8 g a.i./kg seed reduced the viable endophyte level from 70 to 0% in the greenhouse with seed treated with a commercial seed treater 3 mo postharvest. Effects of the fungicides on seed germination varied with formulation and rate but in most cases were not significant (P = 0.05) by final germination count. In field plantings of seed treated with a commercial seed treater using triadimenol or triadimefon at 4.8 g a.i./kg seed, control ranged from 50 to almost 100%; variations in control were possibly due to soil differences among planting locations.

Keyword(s): Epichloë typhina.