Iris yellow spot virus (IYSV) has become a production constraint to onion bulb and seed crops in the Pacific Northwest region of the U.S. and many other areas of onion bulb or seed production in the world. First described from the Treasure Valley of Idaho in the early 1990s, epidemics have been observed in both onion bulb and seed crops since 2000. Characteristic symptoms include diamond-shaped lesions on scapes (seed stalks) which may expand and coalesce leading to drying and eventual lodging of scapes. Lesions can be seen on scapes even after the harvest (bottom most scape). Severe cases of lodging may make the crop unharvestable resulting in near or total crop loss.

APS publication number: IW000075

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