Economic Thresholds of Wheat Streak Mosaic in the Texas High Plains

Abstract

Core Ideas Expected wheat yield declines exponentially with increasing wheat streak mosaic severity. For reflectance readings taken on 27 April, 4 May, and 10 May, economic threshold reflectance values are 8.3, 9.5, and 9.4, respectively. At the threshold infection severity expected grain yield is approximately 1910 kg ha−1. Wheat growers could potentially save resources by discontinuing input applications and introduce cattle for grazing. Wheat streak mosaic (WSM), caused by Wheat streak mosaic virus, is the most widespread and economically important virus disease affecting winter wheat (Triticum aestivum L.) in the Great Plains of the United States. Using reflectance data from a hand‐held hyperspectral radiometer and yields from a field experiment, this study estimated economic thresholds of WSM beyond which it is uneconomical to continue with mid‐season input applications. Disease severity assessments based on reflectance measurements were taken from 99 plots across the field at three time points, namely 27 April, 4 May, and 10 May in the 2015–2016 wheat season. A log‐linear regression model of yield on reflectance indicates potential yield losses of up to 35% for every unit increase in infection severity (as measured by reflectance readings). Using regression and partial budget analysis, results show varying thresholds of WSM depending on the date of disease severity assessments. The 27 April assessment had the lowest threshold when compared with the other assessment dates. Threshold analysis indicates potential to save resources by discontinuing mid‐season input applications and introducing cattle for grazing, in about 14% of the sampled plots, but only 1% if grazing was not possible.