How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Big vein disease 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. Severely affected plants can be so deformed as to be unmarketable, and head lettuce varieties may fail to form a head. However, infected plants showing less severe symptoms can still be harvested.

COMMENTS ON THE DISEASE

The virus that causes big vein is soilborne and is introduced into lettuce plants by a soil fungus (Olpidium brassicae) that attaches itself to lettuce roots. Even though the virus 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.

MANAGEMENT

In fields having chronic and severe big vein histories, avoid planting susceptible cultivars during spring. Some big vein resistant cultivars are now available. Crop rotations are not effective in controlling big vein. No other control options are suggested.

Organically Acceptable Methods
Cultural controls are organically acceptable.

PUBLICATION

UC IPM Pest Management Guidelines: Lettuce
UC ANR Publication 3450
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
R. M. Davis, Plant Pathology, UC Davis

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