Turnip yellow mosaic virus (TYMV)
This virus only infects crucifers. In cauliflower, symptoms begin as vein clearing, but subsequently develop into permanent yellow patches on older leaves. Symptoms on Chinese cabbage develop into bright yellow and dark green mosaic patterns. During cool weather, infected plants remain stunted. Symptoms are mild in other brassicas.
Conditions for Disease Development
This virus overwinters in cruciferous weeds. Turnip yellow mosaic virus is generally transmitted by chewing insects such as flea beetles, mustard beetles, grasshoppers and earwigs. Temperatures near 25°C (77°F) are optimal for symptom development.
Use insecticides to help control insect populations. Eradicate cruciferous weeds and volunteers.