Wheat Disease Update – 1 April 2025
Meriem Aoun
Small Grains Pathologist
Department of Entomology & Plant Pathology Oklahoma State University
Disease pressure in Oklahoma remained low throughout March 2025. However, symptoms of wheat soilborne mosaic virus (WSBMV) and wheat spindle streak mosaic virus (WSSMV) were observed at two locations: the OSU Entomology and Plant Pathology farm in Stillwater and the OSU North Central Research Station in Lahoma (Garfield County) around the second week of March (Figure 1). Once a field is infected with WSBMV, the only effective management strategy is planting resistant varieties. Fortunately, most hard winter wheat varieties in the Great Plains are resistant to this virus. WSSMV can co-infect alongside WSBMV but is generally less damaging and less widespread in Oklahoma. A few varieties are resistant to wheat soil-borne mosaic but susceptible to wheat spindle streak mosaic.
On March 14, 2025, a wheat sample from a grower’s field in Garber (Garfield County) tested positive for both WSBMV and wheat streak mosaic virus (WSMV). WSMV is spread by the wheat curl mites, which oversummer on alternative hosts like corn, volunteer wheat, and grassy weeds. Because wheat curl mites have a short lifespan (7–10 days), the best strategy for managing WSMV is to make sure that these alternative hosts are completely dead at least two weeks prior to wheat planting. A few wheat varieties, including the OSU variety ‘Breakthrough’, are resistant to WSMV.
Figure 1. Wheat showing yellowing and stunting was infected with wheat soilborne mosaic virus (Lahoma, OK; 11 March 2025. Photo Credit: Brett Carver).
No stripe rust or leaf rust has been observed or reported in Oklahoma so far. However, rust infections have been observed in Texas as early as February 26. Brandon Gerrish (Assistant Professor & Extension Specialist, Texas A&M University) reported low levels of leaf and stripe rust in wheat plots in College Station on February 26. Tyler Mays (IPM-Hill County) reported trace levels of stripe rust north of Waco. In early March, leaf rust was found in minor levels near Castroville and McGregor and at trace levels at Uvalde. We will continue monitoring the rust situation in Oklahoma and provide updates as needed.