Big vein disease is a viruslike disease that causes the veins in leaves to become very enlarged and clear. Such deformities are easily seen if the leaf is examined with the light source behind it. The enlarged veins cause the rest of the leaf to be ruffled and malformed.
Life cycle
Big vein is caused by an unidentified viruslike agent. This agent is soilborne, and is introduced into lettuce plants by a soil fungus (Olpidium brassicae) that attaches itself to lettuce roots. Even though the agent is soilborne and therefore always present in infested fields, disease severity may vary greatly from season to season. Big vein is more prevalent and severe during cool weather.
Solutions
Lettuce big vein is caused by a viruslike agent vectored by the fungus Olpidium. There is little that can be done to manage it. Avoid fine-textured, poorly drained soils where big vein has been a problem. Do not overirrigate. Symptoms are not as severe if air temperatures are above 60°F, so a change in planting time can help. Some varieties may be more tolerant.
