June 16, 2004
Stripe Rust Update and Fungicide Application
Xianming Chen
Wheat stripe rust is now almost everywhere in Washington,
western and northeastern Oregon, and northern Idaho with various severity
levels. I was checking commercial
fields in Whitman and Spokane county of Washington along Highway 195 and
Benewah and Latah counties of Idaho along Highway 95, and found stripe rust in
all regions. Dr. Jim Peterson and
Richard Smiley of Oregon State University reported wheat stripe rust in the
Pendleton area and western Oregon.
In Lind, WA, susceptible winter wheat varieties in our
experimental field had up to 30% rust severity by June 10. Varieties Hatton, Buchana, CDC Falcon, Columbia
1, and Quantum had 20% rust; and Basin, Wanser, WPB 470, Symphony, and Walladay
had 10-15% rust. Susceptible spring
wheat had up to 10% rust.
On June 10, Kim Kidwell, Gary Shelton and I checked spring
wheat plots in Moses Lake, WA.
Susceptible varieties had up to 90% of rust severity. Varieties that were susceptible or
moderately susceptible (with 40-90% of infection severity and abundant rust
pustules) included Fielder, Edwall, Penawawa, Zak, Wawawai, Calorwa, Treasure,
Whitebird, Eden, Macon, and Scarlet.
Application of fungicides is necessary for fields grown with above winter
and spring wheat cultivars.
Resistances in winter wheat varieties like Eltan, Madsen,
Rod, Stepthens, Hill 81, Bruehl, Rely, Coda, Chukar, Finch, Lambert, Finley,
and many others are effective and adequate.
Fungicide application is not needed for fields grown with these
varieties. Similarly, spring wheat
varieties Wakanz, Nick, IDO377s, Lolo, IDO597, Blanca Grande, Hollis, Tara
2002, Jefferson, and Jerome are still resistant and fungicide spray is not
needed. Variety Hank was resistant in
the Moses Lake nurseries. Hank fields
should be watched closely for changes of stripe rust reaction.
Varieties Alpowa and Express have moderate level of
high-temperature, adult-plant resistance, which is generally adequate under
normal weather and rust conditions.
This type of resistance does not change with races of the rust, but
under the influence of temperature, plant growth stage, and rust inoculum
pressure. For example, Alpowa had 50%
of severity but mainly dead leaf tissues with limited number of rust pustules
in the Moses Lake field plots by last week.
When checked on June 16, Alpowa fields had 2-10% of severity with
resistant to susceptible reactions in Whitman, Spokane, Benewah and Latah
counties. Based on our research, Alpowa
can have yield losses up to 20%, much lower than 60% for susceptible
varieties. This year, Alpowa fields may
potentially suffer yield losses of between 5 to 15%. Whether to spray Alpowa and Express fields or not depends upon
yield potential in your area.
Based on the weather forecast for next 10 days, temperatures
will continue being favorable for stripe rust.
Current moisture condition in the Palouse region is still adequate and
temperatures are just perfect for stripe rust infection and development. Under current conditions, it takes two to
three weeks from infection to rust appearance.
Wheat crops in eastern Washington, northern Idaho, and northeastern
Oregon have been under stripe rust infection roughly since mid May. Therefore, stripe rust of wheat will
continue increasing even without more precipitations for the next three
weeks. It is good that many fields of
susceptible wheat have been sprayed with fungicides. If your fields of susceptible varieties mentioned above or other
varieties susceptible have not been sprayed, please consider to spray. Now is the right time for fungicide
application. The currently registered
fungicides (Tilt, Quadris, Headine, Stratego, and Quilt) are systematic and
their effectiveness generally lasts about one month. One application should be generally adequate for the eastern
Pacific Northwest. Please keep in mind
that all registered fungicides cannot be used after Feeks stage 10.5 (late
heading stage) or within 45 days before harvesting.
Barley stripe rust was found in our experimental field in
Lind, WA last week, and also found in a field of a 6-row barley north of
Steptoe along HW 195 at the 59 milestone on June 15. Although the rust level is low, it will develop quickly in the
susceptible field and other fields of susceptible barley varieties like
Steptoe, Morex, and Harrington.
Therefore, fields of such barley fields should be watched closely and
fungicide application should be considered if stripe rust develops to 5-10% of
severity. Stripe rust has not been
found in barley fields appearing like Baronesse that has moderate level of
high-temperature, adult-plant resistance.
If you have any questions, please contact me (509-335-8086, xianming@mail.wsu.edu) or David Wood
(509-335-4789, dawood@mail.wsu.edu).
