NPIPM:Wheat streak mosaic
Authors:
Causal Organism
Wheat streak mosaic is caused by Wheat streak mosaic virus", or WSMV.
Symptoms and Signs
The most common symptoms of WSMV are stunted growth and yellowing. Infected plants will show yellow and green streaks parallel to the leaf’s veins. Leaves will curl inwards and sometimes young leaves get “trapped” due to the presence of a high population of wheat curl mites, the vector of WSMV. Symptom severity can vary based on the cultivar, time of infection (fall vs spring infection), and environmental conditions. Warm fall and dry and warm spring increase symptom severity.
Disease Impacts
Wheat streak mosaic virus infections can take place in fall and spring, however, fall infections result in the greatest yield loss. WSMV can drastically reduce both forage and grain yield. An entire field can be lost when plants are severely stunted and cannot be harvested. The disease also reduces the efficiency of water use by the plant, thus also reducing the grain yield.
Life Cycle and Epidemiology
WSMV is spread between winter wheat crops by wheat curl mites (WCMs) moving off volunteer wheat and grassy weeds to the emerging winter wheat in the fall and from winter wheat, volunteer winter wheat or grassy weeds to the spring wheat in spring. The WCMs are not visible to the human eye. When observed under a microscope, the mites resemble small, white grains of rice with two pairs of legs near the head. The mites rely on the wind for transportation from plant to plant. Warm temperatures are optimal for mite reproduction. Temperatures near freezing will stop reproduction, but will not kill the mites. WCMs overwinter in the crowns of winter wheat or in perennial grasses as eggs, nymphs or adults. Spring wheat infection is heavily dependent on the survival of mites during the winter.
Management Approaches
WSMV can be best managed by destroying any volunteer wheat or other grassy hosts (the ‘greenbridge’) at least two weeks before planting the new wheat crop. Greenbridge is defined as volunteer wheat or grassy weeds that provide a habitat for WCMs between the summer wheat crop and the fall sown wheat. Volunteer wheat can be problematic especially when pre-harvest hail threshes some grain to the ground. Plant at the recommended planting dates to avoid optimal conditions for the mite reproduction. There are no known chemical or biological agents that are proven effective for WSMV control. Plant WSMV resistant or tolerant cultivars; a few cultivars have been developed that are resistant to WSMV. Consult your local extension agent for a list of cultivars that are resistant/tolerant to WSMV.
Other Online Resources
A YouTube video summarizing WSMV management https://www.youtube.com/watch?v=yXAmSVqW0xc
Animation video on wheat-mite-virus complex https://www.myfields.info/wheat-mite-virus-complex
Related NPIPM/HPIPM Resources
https://www.myfields.info/disease/wheat-streak-mosaic-virus
