Lettuce big-vein disease

Lettuce big-vein disease causes leaf distortion and ruffling in affected lettuce plants.
This disease was first associated in 1983 with a rod-shaped virus named lettuce big-vein associated virus, which is transmitted by the obligately parasitic soil-inhabiting fungus, Olpidium brassicae. However, in 2000, a second virus, Mirafiori lettuce big-vein virus, was found in lettuce showing big-vein symptoms. Furthermore, since the lettuce infected with LBVaV alone doesn't develop the symptoms while the infected with MLBVV one does, the latter virus is considered to be a main agent of the big-vein disease.

Symptoms

Affected plants have veins that become large and clear, causing the rest of the leaf to become ruffled. Severely infected plants may fail to form a lettuce head.

Control

Grow disease-resistant cultivars.
Use disease-free healthy seeds.
Treat with methyl bromide, chloropicrin, or dazomet solution.