ABSTRACT
Introduction and significance Beet western yellows is an occasional virus problem of lettuce in North America and Europe. Diagnosis of this disease may be complicated because symptoms caused by this virus can closely resemble those of nutrient deficiencies
Symptoms and diagnostic features Symptoms usually do not develop until plants reach rosette stage or later. At this point in crop development, the leaves develop chlorotic blotches in interveinal tissue. This yellowing continues until the oldest, lower leaves are bright yellow to sometimes almost white in color, with the main leaf veins remaining green (423, 424). Yellowed leaves often have a thick, brittle texture. Yellowing can progress until the wrapper leaves adjacent to the head also turn yellow, and head color may be unacceptably light green. In most lettuce varieties, significant stunting or reduction in plant size does not occur. Overall symptoms of this yellows disease may resemble iron chlorosis.
