Thursday, May 5, 2011

Stripe rust update, May 5, 2011

Mike Flowers, Chris Mundt, Larry Lutcher and Mary Corp, of Oregon State University, provided the following information in their Stripe Rust Seminar this morning. The webcast seminar connected 8 sites across eastern Oregon with over 30 growers and crop consultants in attendance to learn the latest update on stripe rust conditions across the wheat growing regions of the Columbia Plateau and central Oregon. Here are some of the topics covered:

Stripe rust pressure continues to build across the region, but the answer to the dilemma is in the details of each grower’s field conditions, stage of growth and wheat variety susceptibility to stripe rust. Growers are faced with questions both about what is currently happening in their fields and then also what are their best options for seeding this fall. OSU Extension webcast this morning focused on these two key questions for wheat growers across the Columbia Basin: Do I need to treat a second time for stripe rust? And what wheat variety should I be planting in the fall of 2011?

Both questions center on the level of susceptibility of the various wheat varieties and the current strains of strip rusts being seen in fields. Mike Flowers, OSU Cereal Specialist, noted that he sees about three grouping of varieties –
  • Highly susceptible, 
  • Moderately susceptible, and 
  • Mostly resistant.

So far this year, Flowers has observed that varieties that are holding up well under dryland conditions are ORCF 101 and Skiles. This is the same result he saw last spring when stripe rust conditions were a problem. Yet it is worth noting that this year, the problems started last fall and have continued to increase under our cool wet spring conditions.

The next level of susceptibility with only moderate resistance or susceptibility, depending on if your cup is half empty or half full, are the varieties - Legion, ORCF 102 and Stephens. Finally, the most susceptible are Tubbs, Xerpha, Legacy and Goetze.

Many acres had an earlier application of fungicide applied at the same time as the herbicide. The stripe rust control provided by those applications are running out, and fields with susceptible varieties need to be closely monitored. Remember if you see 10% live spores on the leaves, then you likely have 40-50% infection as there is a 2 week delay in appearance of the spores following infection.

Flower’s summary remark at the end of today’s broadcast – was “Don’t let it (stripe rust) get ahead of you.” Many fields are currently seeing stem elongation, but don’t yet have flag leaf emergence. Plants usually show 4 joints on the stem prior to the flag leaves according to Lutcher. These plant development stages are helpful in gauging the timing of fungicide applications to maximize the control window during late spring applications. The real world realities of getting the application scheduled and finding enough good hours to get the application on the field may be a greater deciding factor about pulling the trigger for many growers especially with highly susceptible varieties to moderately susceptible varieties.

Chris Mundt, OSU Pathologist, also added the caveat that when the wheat plant reaches the flowering stage it is too late to have any affective control of the stripe rust with fungicide application so growers need to realize that if the treatment window get passed there is no benefit in continuing to treat.

Next week, we can talk more about the question of what to plant this fall,

If you have additional comments and thoughts, please post below.

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