Wheat growers across Oklahoma are facing renewed pressure from pests and diseases this spring, led by the re-emergence of wheat streak mosaic and ongoing concerns tied to drought and shifting weather conditions.
According to Meriem Aoun, small grains pathologist at Oklahoma State University, the current situation is largely a continuation of conditions that developed during the 2024–25 wheat season.
“Given last wheat season conditions, this was not a surprise,” she said.
Aoun said the wheat curl mite transmits a wheat virus complex including wheat streak mosaic virus, Triticum mosaic virus, and High Plains wheat mosaic virus.
“Around harvest last year, we experienced substantial precipitation, which delayed harvest and favored the establishment of volunteer wheat, allowing wheat curl mites to survive over the summer,” she explained. “Because wheat curl mites require living green tissue to survive, volunteer wheat and grassy weeds act as a “green bridge,” enabling mites and the viruses they carry to move into the next wheat crop emerging in the fall.”
Wheat streak mosaic confirmed
Aoun said fall infection is more damaging to yield in comparison to spring infection, and WSM is expected to be as bad this year as it was last year. In March 2026, the OSU Plant Disease and Insect Diagnostic Lab confirmed WSMV in wheat samples received from multiple wheat fields in Blaine, Garvin, Washita, Beaver, Texas, Cleveland, Kay, Payne, and Noble counties.
Aoun said wheat streak mosaic virus is the most widespread of the three viruses identified in Oklahoma fields this season. In several cases, samples showed co-infection with Triticum mosaic virus and/or High Plains wheat mosaic virus, which can intensify symptoms and lead to greater yield losses than a single-virus infection.
Infected plants often show stunting and streaked or mottled leaves. As infections progress, discoloration can worsen, with some viruses causing distinct spotting that develops into yellowing and necrotic tissue.
She said WSMV is the most widespread virus in samples collected in Oklahoma fields. In some samples that were infected with WSMV, they were also co-infected with TriMV and/or HPWMV. Co-infection of two or more of these viruses can increase symptom severity and yield loss over the effects of a single virus infection, Aoun said.
The factors we can and cannot control
The harsh weather conditions that have plagued the High Plains this spring have been a contributing factor to the spread of pests and diseases they can vector.
“Current dry and windy conditions have generally favored some wheat insect pests like brown wheat mites, which thrive in drought conditions, and wheat curl mites, which rely on wind to move between plants and between fields,” Aoun said. “Over the last few years, drought conditions favored dryland root rots, including common root rot and Fusarium crown or root rot.”
Aoun said even with these severe, dry conditions, leaf rust and stripe rust were observed near Stillwater on March 31.
“As leaf rust is active in Texas; wind can transport leaf rust pathogen spores from Texas to Oklahoma and contribute to the disease development this spring if moisture increases,” she added.
A widespread rain event took place across most of Oklahoma on March 31, bringing with it much needed moisture. Aoun said although this should improve crop establishment, continued wet conditions late into the spring, could increase the risk of foliar fungal diseases like rusts and leaf spotting diseases, particularly in susceptible varieties.
“It is also likely that dryland root rots will be an issue this year in drought-stressed fields, as in the previous four growing seasons,” she said. “Aphids and barley yellow dwarf virus may also be issues. We observed a high incidence of BYDV near Stillwater. There were also reports of bird cherry oat aphid in southwest Oklahoma and greenbugs in central Oklahoma in March, and both of these aphids can transmit BYDV.”
Aoun said there is no in-season rescue treatment for wheat streak mosaic. Management efforts must focus on preventing future infections, including destroying volunteer wheat and grassy weeds at least two weeks before planting.
“Because wheat curl mites move easily between fields by wind, controlling the green bridge works best when neighboring producers coordinate management efforts; avoiding early planting when mite populations are high; and choose varieties with wheat streak mosaic virus resistance, if possible.”
Lacey Vilhauer can be reached at 620-227-1871 or [email protected].
