A perfect storm of weather conditions created an ideal environment for wheat curl mites to thrive following the 2016 harvest. The wheat streak mosaic virus epidemic that resulted has cost Kansas farmers — especially in the western part of the state — millions of dollars in lost yields.
Six counties (Greeley, Wichita, Lane, Hamilton, Kearny and Finney) saw heavy pressure from wheat streak mosaic as well as High Plains mosaic and triticum mosaic viruses, with losses expected to be as high as 70% to 100% in many fields. Other mosaic viruses often attack plants already weakened by WSMV.
Central and southern Kansas saw moderate infection rates and losses as high as 50% in infected fields.
Weather conditions contributing to the infection rate included a wet harvest and postharvest season, which helped promote heavy germination and growth of volunteer wheat, and a very long, warm fall, which meant newly planted wheat was green and growing well into November.
No wheat varieties have strong resistance to WSMV, and those that do have some resistance see a breakdown of protection in warm temperatures, which lasted until late in the fall.
The setup for a continuation or even worsening of the problem is already well established in postharvest 2017, and plenty of producers, research and Extension leaders, crop consultants, and angry neighbors are stepping up efforts to push the one remedy most effective in stopping the losses: Control the volunteer wheat in harvested fields. Killing the volunteer wheat well ahead of fall planting of the 2018 crop deprives the mites of food, and they die off before they can infect the new crop.
There is no effective chemical control for the mites that are the vector for wheat streak mosaic. There is no effective treatment to kill the virus or heal damaged plants. There are only a few varieties that show some resistance to infection, and they are by no means able to combat a heavy infestation, which Kansas most certainly has.