Lettuce big-vein disease

Lettuce big-vein disease
Causal agents	Lettuce big-vein associated virus
Hosts	Lettuce
Vectors	Olpidium brassicae
Treatment	See text

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 virus, was found in lettuce showing big-vein symptoms. Furthermore, since the lettuce infected with this virus alone developed big-vein symptoms, it is considered to be a main agent of the big-vein disease.

Symptoms

• Big vein (Mirafiori lettuce big-vein virus or MiLBVV)
• Veins enlarge, clear and show yellow discolouration. Leaves become puckered or ruffled and ultimately thicken. The outer leaves become upright. Virus is soil borne and is introduced to plants via Olpidium brassicae fungus. Disease is more prevalent during cool weather.

Control

• Grow disease resistant cultivars.
• Use disease free healthy seeds.
• Drench the field with methyl bromide, chloropicrin, or dazomet solution.