Cause The aster yellows phytoplasma is transmitted by several leafhoppers and has a very wide host range.
Symptoms First symptoms are blanching and chlorosis in young heart leaves. Center leaves fail to develop normally and may appear as short, thickened stubs. Pink to tan latex deposits collect on affected leaves. In plants infected late in the season, the only symptoms are latex deposits within the head. In general, infected plants are stunted, fail to head, and are worthless for market.
- Eliminate weeds in areas surrounding the lettuce planting.
- Controlling leafhopper vectors may give partial control.
- Leafhoppers avoid shaded plants.