|WORKNEH, FEKEDE - Agrilife Research|
|Evett, Steven - Steve|
|RUSH, CHARLIE - Texas Agrilife Research|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2017
Publication Date: 8/22/2017
Citation: Workneh, F., O'Shaughnessy, S.A., Evett, S.R., Rush, C.M. 2017. Relationships between early spring wheat streak mosaic severity levels and grain yield: Implications for management decisions. Plant Disease. 101(9):1621-1626.
Interpretive Summary: Approximately three million acres of winter wheat are grown in the Texas High Plains region, with one-third of the wheat irrigated. The wheat is used for grain production and forage for cattle grazing. A critical issue for farmers is that the wheat is susceptible to Wheat streak mosaic virus (WSMV), which is transmitted by the wheat curl mite. If infected early in the season, the wheat will produce little to no yield. Scientists with Texas A&M AgriLife Research and ARS-Bushland demonstrate in this study that a handheld spectral-radiometer with photodetectors in the green band (555 nm) can be used to identify WSMV infection in the field in early spring. The level of reflectance from the green band is positively correlated with the level of disease severity and inversely related to grain yield. This is an important finding, as early detection with this proximal sensor can lead to improved crop water use efficiency and help limit water wastage.
Technical Abstract: Wheat streak mosaic (WSM) caused by Wheat streak mosaic virus, which is transmitted by the wheat curl mite (Aceria tosichella), is a major yield-limiting disease in the Texas High Plains. In addition to its impact on grain production, the disease reduces water-use efficiency by affecting root development. Because of the declining Ogallala Aquifer water level, water conservation has become one of the major pressing issues in the region. Thus, questions are often raised as to whether it is worthwhile to irrigate infected fields in light of the water conservation issues, associated energy costs, and current wheat prices. To address some of these questions, field experiments were conducted in 2013 and 2016 at two separate locations to determine whether grain yield could be predicted from disease severity levels, assessed early in the spring, for potential use as a decision tool for crop management, including irrigation. In both fields, disease severity assessments started in April, using a handheld hyperspectral radiometer with which reflectance measurements were taken in multiple plots across the fields over time. The relationship between WSM severity levels and grain yield for the different assessment dates were determined by fitting reflectance and yield values into the logistic regression function. The model predicted yield levels with r2 values ranging from 0.67 to 0.85 (P less than 0.0001) indicating that the impact of WSM on grain yield could be fairly well predicted from early assessments of WSM severity levels. As the disease is normally progressive over time, this type of information will be useful for making management decisions of whether to continue irrigating infected fields, especially when combined with an economic threshold for WSM severity levels.