Cauliflower mosaic virus (CaMV)
Worldwide, especially in temperate areas of the United States and Europe
Only members of the crucifer family are susceptible to CaMV. Systemic symptoms consist of a clearing or chlorosis along leaf veins (vein clearing). This is often seen first at the base of a leaf. Later, symptoms appear as dark green areas along veins (vein banding) and necrotic spotting of the leaf. Chinese cabbage is particularly susceptible to CaMV. In addition to vein clearing, a striking mosaic may develop with light and dark green areas on leaves. Plants can be stunted. Internal necrotic spotting in stored cabbage has been attributed to CaMV infection.
Conditions for Disease Development
The primary inoculum source of CaMV is infected brassica crops or cruciferous weeds. The virus is transmitted to the crop by many species of aphids, such as the cabbage aphid, the false cabbage aphid and the green peach aphid. Aphids can acquire and transmit CaMV within one minute of feeding on an infected plant. Temperatures between 16- 20°C (61-68°F) favor symptom expression in plants. CaMV is often found as a mixed infection with Turnip mosaic virus, resulting in more severe symptoms than when either virus is present alone.
Eradicate cruciferous weeds and volunteers, and incorporate crop debris immediately after harvest. Isolate transplant beds from commercial crucifer crops.