Stripe Rust Update, Dr. Chen

Stripe rust started earlier in the Milton Freewater, Walla Walla and Dayton (Columbia County)area than in other areas of the region this spring. Dr. Chen, WSU, was able to take preliminary notes in the variety trial near Dayton on June 7 and 8th.  Here are his observations and recommendations:

• Stripe rust reactions of the most of tested varieties were as expected with some exceptions.   
• Rod, SWW variety, had more susceptible plants than in the past, indicating a considerable proportion (estimated as 20%) of plants became susceptible.   
• Tubbs 06, SWW variety, became more susceptible than in the past a couple of years after the re-selection from ‘Tubbs’. 
• Lambert had very high severity (40-80%),even with a moderately resistant reaction.   
• The changes towards more susceptibility of these two varieties are not only due to the low temperature and high moisture conditions this year, but also possibly due to changes of races and their frequencies.

Based on Dr Chen notes in this variety trial and previous data, the unique weather conditions, and HTAP resistance has started kicking in, he is grouping the major varieties into the following three groups and rating the need to spray fungicide applications:

Varieties should NOT be sprayed:  Eltan, Madsen, Eltan/Madsen, Chukar, Finch, Skiles, ORCF-102, ORCF-103, Coda, Madsen/Rod, Legion, Bitteroot, Bruehl, Stephens, Brundage 96, Eltan/Tubbs06, KCF9002, RJames, Goetze, Goetze/Skiles, Cara, and George.

Varieties should be sprayed: AP Legacy, Salute, KCF9003, CDC Ptarmigan, Paladin, Eddy, Finley, Finway, and Buchanan.

Varieties can be either sprayed or not sprayed:  Tubbs 06, Simon, Xerpha, Rod/Tubbs 06, Rod, Lambert, Masami, WB-528, AP700CL, Farnum, and Bauermeister.  The difficulty to make a decision of spray or not spray for varieties in this group is due to the inadequate levels of HTAPWalla Walla, Columbia, and Garfield counties and southwestern Whitman County as rust severity has reached to significant levels and expected to increase more in another week or so.  In most of the other areas, rust levels are still quite low and we expect that HTAP resistance starts to work in most of these varieties as the weather is going to warm up next week.  The second consideration is the yield potential.  The higher yield potential, the easier to justify the cost of fungicide application.  A general guideline is that fields of 100 bushel per acre should move toward spraying as yield losses of such varieties may range between 5 to 15%. 

In addition to Tilt, Quilt, Quadris, Stratego, and Headline, Folicur can be used. 

Spring wheat has a much wide variation in growth stages, from tillering to flag leaf stage across the Pacific Northwest, particularly in Washington State.  Rust is in spring wheat fields, but in very low incidence and severity (less than 2%) in general.  If susceptible varieties (such as Scarlet, Hank, Nick, Eden, Westbred 926, Tara 2002, Jefferson) are grown, you may consider an early spray before rust reaches 10% severity or incidence as you may be able to use ground application in early stage.  If resistant varieties (such as Louise, Wakanz) are grown, fungicides may not be used you should not use fungicides.  Alpowa is in between and we hope its HTAP resistance starts working as the weather becomes warm.

Dr. Chen found a very low level of stripe rust on barley in a couple of fields in Whitman County, not warrant immediate spray.  People should check their fields for stripe rust and its increase.  If moderately resistant varieties (such as Baronesse and Bob), spray may not be necessary.  If other varieties (mostly susceptible) are grown, spray may be needed in a week or two when rust reaches about 10% severity or incidence.

Stem rust:  The rust samples we collected from barberry bushes in the Latah County Idaho and Whitman County, Washington last month have been identified as stem rust.  We couldn’t found any stem rust in the wheat fields nearby the barberry bushes in the Latah County today.  Rust reached last stages of aecial on the bushes.