Wheat streak mosaic

The disease is caused by the wheat streak mosaic virus (WSMV), which belongs to the genus Rymovirus. It is a filamentous plant virus that causes significant economic losses in various grain crops worldwide. The virus disrupts the normal physiological processes of plants, leading to systemic infection.

The primary host for the virus is quackgrass (Elymus repens), which acts as the main reservoir for the pathogen throughout the year. The virus also infects a wide range of monocot species, including winter and spring wheat, barley, and various wild grasses. The persistence of the virus in perennial grasses makes it a permanent threat to neighboring cereal fields.

Symptoms of the infection typically appear as yellow mosaic patterns, streaks, and stipples on the leaves. Infected plants often exhibit stunted growth, reduced tillering, and general chlorosis. In severe cases, the grain heads may fail to develop properly, resulting in shriveled kernels and significantly reduced biomass.

Transmission occurs through the wheat curl mite (Aceria tosichella), which picks up the virus while feeding on infected plants and transfers it to healthy ones. The mite can be carried by wind over long distances, facilitating the spread of the disease across regions. High temperatures and drought conditions can sometimes exacerbate the impact of the disease by stressing the plants.

Crop loss depends on the timing of the infection; early-season infections cause the most damage. Management strategies focus on breaking the infection cycle:

• Eliminating volunteer wheat and perennial grass weeds like quackgrass before planting.
• Delaying fall planting to reduce the window of exposure to mite vectors.
• Selecting and planting resistant or tolerant grain varieties.
• Maintaining spatial separation between older, infected crops and new plantings.