Field Monitoring

To monitor the prevalence and severity of stripe rust and to detect the
changes in virulence of the pathogen, trap plots of winter wheat and/or
spring wheat were planted annually from 1968 to 1987 in commercial
fields or at experiment stations. The plots consisted of single 1.5- to
4-m rows of past and current commercial cultivars, new improved lines
of wheat, and cultivars and lines that differentiate races of P.
striiformis in North America and Europe. Initially, all of the
monitoring sites were in the Pacific Northwest, but as the need became
evident, sites were added at other locations in the Western United
States where stripe rust occurred. In 1986 and 1987, additional
monitoring sites were established in Colorado and at several locations
in the South-Central United States. Each year, the trap plots were
planted at 15-25 sites. The winter wheat plots were planted in fall;
the spring wheat plots were planted in fall in central California and
in spring at other sites. Wheat cultivars and lines in national uniform
disease nurseries, international rust nurseries, regional and breeding
nurseries, and demonstration plots were also used to provide
supplemental data on rust. The plots were visited one to five times
during the growing season; on each visit, rust intensity (severity),
infection type (table 1, fig. 1), and stage of plant growth were
recorded for each cultivar or line in the plots. Plots at sites within
600 km (375 miles) of Pullman, WA, were most frequently examined. When
visits to more distant sites were not possible, some disease data were
recorded by cooperators. When traveling to and between the sites, we
made frequent stops to examine commercial fields and recorded data on
rust severity, infection type, and stage of growth for those fields.