Survival ofVerticillium albo-atrumin Alfalfa Tissue Buried in Manure or Fed to Sheep

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Abstract
A study was carried out to determine the survival of Verticillium albo-atrum in diseased alfalfa tissue when buried in manure or fed to sheep. Alfalfa stems naturally infected with V. albo-atrum were buried in indoor cow manure peaks and in an outdoor manure pile. Stems were recovered at intervals over 6 wk and examined for viable V. albo-atrum in the tissue. The rate of survival of V. albo-atrum in the stems buried 10, 30, or 60 cm deep for 1 wk was 0-26%, but was 54-90% in the stems buried near the surface of the manure pile. In the outdoor experiment, V. albo-atrum was viable in 93% of the stems near the surface of the manure pile after 6 wk. When alfalfa hay infected with V. albo-atrum was fed to sheep, the pathogen was present in feces collected within 2 days. The maximum number of Verticillium propagules in sheep feces collected each day was 19 and 29 per dung ball for the experiments in 1982 and 1983, respectively. V. albo-atrum did not persist in the digestive tract and was absent in feces collected two or more days after the animals were returned to a diet free of the pathogen.