Cauliflower Mosaic Virus (CaMV)
It shows systemic symptoms such as a clearing along the leaf veins (vein clearing). This often is 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 seen on the leaves. Plants can be stunted. The main source of CaMV are plants of an infected brassica crop or cruciferous weeds on which a vector has over-seasoned. The virus is transmitted by many species of aphids, such as the cabbage aphid.
- Adequate weed control and sanitation should be practised.
- Plough-down previous crops rapidly.
- Transplant beds should be isolated from commercial crop fields and overwintering cruciferous weed hosts.