What a difference a year makes. Last year there was a considerable scrambling to apply fungicides for stripe rust control due to high levels of inoculum, ideal conditions for disease development, delayed plant development, and unfavorable spraying conditions. This year, beyond early fungicide-herbicide tank mixed applications, there has been little if any evidence of the disease, and little need for late season applications.
We have followed stripe rust reports from western OR and eastern WA and stripe rust is much less prevalent there than last year. The same is true of eastern ID. Susceptible varieties at Parma and across southern Idaho have been clean with no rust present. Also, we have earlier plant development, and higher temperatures should allow high temperature adult plant resistance (HTAP) to occur. Consequently, varieties with HTAP resistance should be able to ward off any late infections if they occur. Even susceptible varieties will escape injury this season if late infection occurs much beyond the present.
Last year’s infection was evident in the first week of May. It hadn’t appeared at Parma in susceptible varieties by the end of May. Even where highly susceptible varieties volunteered in fall 2011, these varieties have no evidence of stripe rust infection despite a fair amount of inoculum available last summer and possibly in the fall. A late stripe rust infected field was reported in late May in the Magic Valley. Most all early planted winter wheat is flowering. Late planted winter wheat was heading or flowering on May 28. For most winter wheat it will be too late for treatment in western Idaho. Spring wheat also is heading but should be scouted.
The stripe rust in 2011 was very educational. It was a wake-up call, a slap in the face for some, of the potential for crop injury and reduced yield potential with severe infections. It also provided an outstanding example of the need for continuing variety improvement. Despite the worst stripe rust severity in the last 36 years at Parma, there were new varieties that came through relatively unscathed yielding over 150 bu per acre. Bruneau and AP Legion were the most resistant and productive soft white winter varieties in 2011, yielding considerably better than other varieties including Stephens, our standard bearer since the late 70’s.
The good resistance for Bruneau is good news. In our Cooperative Extension testing, Bruneau has demonstrated a yield advantage over Stephens with rust and without rust present. Improved stripe rust resistance should hasten its acceptance. Shop early for available seed of rust resistant varieties. Work with your seed dealers to ensure they inventory your varieties of choice.