The rainy and cold spring weather in 2010 is apparently having an effect on head lettuce quality in Salinas Valley fields.
Symptoms appear as very small, brown flecks and spots along the margins of young leaves. Affected leaves are usually found deep within the head. It appears the defects are occurring in multiple iceberg cultivars in various parts of the Valley.
Clearly this is a physiological disorder and superficially looks similar to russet spot. However most of the flecks do not occur on the leaf midribs as would be typical for russet spot.
Russet spot is caused by ethylene production and can occur in mature to over mature lettuce, especially following anaerobic conditions in the field.
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