Farmers in Montana and Canada are already watching disease pressure in winter wheat, as reports of wheat streak mosaic virus have already been confirmed. Symptoms in the fall are unusual, but weather conditions are a large factor. For the past two years, extended fall growth, as well as hail damage, have contributed to heavy pressure from the wheat curl mite, Aceria tosichella, which carries the virus.
“I would say I expect [disease pressure] to be fairly widespread across the state for 2016, but heavier in pockets where it occurred in 2015—near Geraldine, Turner and Great Falls,” says Mary Burrows, associate professor at Montana State University.
Engineering students at Montana State University (MSU) are working on an immunostrip diagnostic tool to help farmers identify the disease. Made with 3D printers, the strip gives a quick reading if the virus is present. Burrows she hopes the tool will be available this spring.
If the virus is suspected, Burrows says to not apply Roundup herbicide, as that makes the mites go to the top of the plant, and are then carried downwind to neighboring fields.
Depending on severity of the disease, she recommends tillage or swathing to terminate damaged fields.
“With these small pockets showing up in winter wheat, I’d hold tight for now,” she says, adding that farmers should scout fields often at green up. “Don’t apply any additional nitrogen to the crop. Nitrogen will make the mites and virus grow and spread faster. In our research, any additional increase yield is counteracted by the increase in disease.”
Spring wheat is even more susceptible to the virus, she adds. “Make sure you don’t plant spring wheat downwind from diseased areas, pay attention to your green bridge and clean up the field.”
Wheat growers in Canada and North Dakota should also be on alert and scout their crops early, she adds.
Nationwide, wheat crop conditions were positive at end of 2015 reporting period. In the 18-state region, 44% of the U.S. wheat crop was ranked in good condition.