In 2017, this disease caused a conservative $76.8 million in direct losses to wheat farmers, a loss of 19.2 million bushels of wheat. The 2017 loss was 5.6% yield loss, up from an average 1.5% loss.
According to the Kansas Cooperative Plant Disease Survey Report, September 28, 2018, wheat streak mosaic virus complex (WSM) was the third most important disease of 2018, at 0.07% estimated loss statewide, or 194 thousand bushels.
This is an unusually low yield loss due to this disease, much lower than the 5-, 10-, and 20-year averages (1.69%, 1.28%, and 1.32%, respectively). This is in stark contrast to the yield loss in 2017 (5.6%), a year of unusually severe WSM due to decreased control of volunteer wheat in late summer 2016 and weather conditions conducive to disease development.
After such a high loss in 2017, with some observed wheat fields suffering as much as 100% yield loss, farmers may have better controlled the volunteer wheat in post-harvest 2017. This would have decreased the ability of the wheat curl mite to survive between 2017 harvest and planting, which would have better controlled the disease spread. In addition, there was a much more rapid transition to cool temperatures in the fall of 2017. These cold temperatures in October and November likely reduced the activity and movement of the wheat curl mites.
Wheat streak mosaic virus complex is comprised of wheat streak mosaic virus, high plains virus, and Triticum mosaic virus, and is transmitted by wheat curl mites.
In 2018, WSM only caused detectable yield loss in two crop reporting districts, the Northwest and the West Central districts, causing 0.2% and 0.4% loss respectively.
In 2017, central and western Kansas had above average disease intensity.
