Farm Talk

Front page stories

October 22, 2013

Approaching disease from different perspectives


Parsons, Kansas —

In William (Bill) Bockus’s seven year study, Bill assigned a graduate student, Jenna Gaunce, to study how disease incidence affects yield. Counter-intuitively, literature from around the world states that the percent symptoms of BYD do not correlate to the yield loss from that disease. However, as Bockus and Ms. Gaunce have shown, it does matter in Kansas.

In their study, they purposely planted the 12 replicated cultivars two weeks early to ensure infestation of the aphids. Throughout the year, Jenna would rate the plots on a percent symptom basis which would later be compared to the yield data. The results were more staggering than they initially anticipated. The overall r-squared value was 0.29. Simply stated, this meant that across the seven years, 29 percent of the yield of the plot could attributed to the varietal response to BYD.

Using their data, they developed a linear model of Jenna’s observation of disease incidence versus the yield data. The model shows that a very susceptible variety (a 9 on the 1-9 scale) would lose 48 percent of its potential yield from BYD. Bockus also used the popular variety Everest as a comparison. Everest is a 4 on the 1-9 scale which would be considered moderately resistant and lost 18 percent of its yield due to BYD.

Unfortunately, Everest is rated as the most resistant of the 59 varieties rated by K-State Research and Extension in the publication titled Wheat Variety Disease and Insect Ratings 2013. Hopefully, with continued work from dedicated researchers, there will be some more BYD resistant varieties available to producers in the near future. If you have questions or would like more information, please call me at the office 620-724-8233, or e-mail me at, or visit the Wildcat Extension District website at £

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