Friday, May 21, 2010

Stripe Rust Infections Reaching Treatment Levels

Stripe rust has been developing rapidly in Walla Walla and nearby parts of Umatilla County. Since the first observation by Xianming Chen in plots in Walla Walla on April 29, stripe rust has been reported to be widely spread. Plants of a field of ‘Declo’, a susceptible hard red winter wheat cultivar, were quite uniformly infected. Up to 20% incidence was reported in some fields grown with ‘Tubbs 06’ or a mixture of ‘Rod’ and ‘Tubbs 06’.
Dr. Mike Flowers reports significant infection in OSU trials in Hermiston, Pendleton, and Lexington.
Dr. Stephen Guy reported significant infection in one replication of ‘Lambert’ in the variety trial near Walla Walla. Some fields have been sprayed with fungicides in this region. Rust is developing in the Central Ferry area (Columbia County, southeastern WA). Based on Dr. Kim Campbell, ‘Xerpha’ (a soft white winter wheat with a moderate level of high-temperature adult-plant resistance) had infection type 5 and 10-20% severity. Rust has been reported in commercial fields in this area.
Stripe rust management in the PNW:
The current stripe rust situation is similar to what we forecasted in January, little bit more severe than last year, but should be less than 2005. The low temperature and high moisture conditions in the past several weeks and predicted for the next two weeks have been and will be favorable for stripe rust. Under such conditions, fields grown with susceptible cultivars (such as Declo, Buchanan, Finley, Finway, Palatin, and Eddy) should be sprayed. Depending upon locations, cultivars with low to moderate levels of high-temperature adult-plant resistance (such as Farnum, Xerpha, and Baurmeister) may need to consider spraying. Cultivars with high levels of resistance (such as Eltan, Madsen, Stephens, and many others) may not need to spray. Now is the critical time for growers in the Walla Walla, central WA, and nearby regions to check their fields and spray if necessary. Growers in the Palouse region (Whitman County of Washington and Latah county of Idaho) and further north should start to check wheat fields, and consider spraying if rust develops to 5-10% of severity. People also need to consider the fact that several cultivars (such as Tubbs, Tubbs 06, Brundage 96, and many others) are not uniformly resistant, susceptible plants can be found in these crops. Fields grown with such cultivars may need or not need spraying depending upon locations, and a 20% severity threshold may be used to make decision.

This report is based on information provided by Xianming Chen, WSU and Mike Flowers, OSU.

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