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Ecology and Epidemiology

The Effect of Climate Variability on Stripe Rust of Wheat in the Pacific Northwest. Stella Melugin Coakley, Adjunct Assistant Professor, Department of Biological Sciences, University of Denver, Denver, CO 80208; Phytopathology 68:207-212. Accepted for publication 20 June 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-207.

Wheat stripe rust (Puccinia striiformis West) epiphytotics are confined predominantly in the USA to the Pacific Northwest and intermountain states because of the climate. Because stripe rust epiphytotics have been frequent only since 1960, the possibility that climate variability could explain in part the pattern of epiphytotics was investigated. Detailed meteorological data for 1961-1975 were obtained for Pendleton, Oregon; temperature, precipitation, relative humidity, and combinations of these variables were studied for various time segments of data. An increased number of days in January and February with favorable temperatures for rust development could be used to separate years of severe epiphytotics from mild stripe rust years. In 1961-1975, the average temperature in January and February was 2 C higher than for those same months in 1935-1960. In contrast, the average April temperature was over 1.2 C cooler. Warmer-than-normal winter and cooler April temperatures favor the development of stripe rust epiphytotics. Cool spring temperatures delay temperature-sensitive adult-plant resistance in wheat cultivars such as Gaines and Nugaines.

Additional keywords: epidemiology, nonspecific resistance.