Posted July 28, 2015
Hidden in the stubble of 2015’s wheat harvest, wheat curl mites are moving to find sprouting volunteer wheat seedlings to inhabit and continue the life cycle of wheat streak mosaic. The wheat streak mosaic virus instigated by these mites seriously affects the total yield of a wheat crop.
“There were counties out in western Kansas that got hit really hard with the wheat streak this year. Particularly the west central district,” said Bill Bockus, plant pathologist at Kansas State University. “Some of the fields out there got almost completely destroyed, so it is definitely a serious problem.”
Kansas Wheat Commissioner, Jason Ochs said the wheat streak mosaic virus was extremely bad this year in Hamilton County. He reported some of his fields were not cut at all due to the severity of the wheat streak mosaic.
“At first I thought I was only going to harvest 60 percent of what I planted, but it ended up being only 40 percent due to the wheat streak mosaic,” explained Ochs.
Because of the devastating effects of this year’s virus, producers are starting to make decisions that can affect next year’s crop, for both themselves and their neighbors by controlling their volunteer wheat.
The Green Bridge
Wheat curl mites and the virus must have a green host tissue to survive on throughout the summer after harvest. They most commonly reside on volunteer wheat that blew out the back of the combine or shattered grain from hail storms that happened before harvest. The mites on the fallen kernels move to the sprouting volunteer seedlings as new plants emerge in the summer.
“The mites and the virus move from the volunteer wheat that has been growing all summer into the newly seeded wheat crop in the fall,” said Bockus. “This green bridge is what we want to break by killing our volunteer wheat so that the virus and the mites have time to die. Then in the fall the mites are not coming off the volunteer wheat onto our new seeded wheat.”
Behind The Times
Volunteer wheat from abandoned fields or fallen grain can sometime produce impressive stands, but producers should be mindful that they are also full of diseases and insects.
“In the past farmers have always left volunteer wheat for grazing,” said Ochs. “Years ago they could leave that volunteer wheat and it didn’t hurt anything. But in today’s environment we are just not able to do that anymore.”
The best way to manage wheat streak mosaic is to control volunteer wheat after harvest and before planting in the fall. Killing volunteer wheat and grassy weeds with tillage or herbicides at least two weeks before fall planting are both effective ways to exterminate wheat curl mites. These methods kill off the mites as the plants die and dry down because they are unable to survive more than a few days away from green plants
Other factors that aid in the control of wheat streak mosaic are planting tolerant wheat varieties, not planting winter wheat too early and planting high risk fields last. A community effort to control volunteer wheat in stubble fields will also be beneficial in mosaic prone areas with extensive amounts volunteer wheat.
“The biggest thing is that we all have got to work together as farmers and change with the times,” said Ochs. “This is a different time than it was 15 or 20 years ago when we didn’t have to control volunteer wheat.”
By Audrey Schmitz