On Crops: Spinach, lettuce, cucumbers, peas, and many flowers and weeds
Mostly in warm temperate climates, where CMV is transmitted by aphids.
On young plants, CMV causes leaves to become twisted and partially folded, and grow slowly. When mature spinach plants are infected, mottled patches of yellow and green develop on older leaves, and new leaves close to the center may be small, yellow and twisted.
Like other plant viruses, cucumber mosaic virus interferes with genetic signaling within the plant. Leaves that are distorted by the virus cannot function normally, so plants struggle to grow and stop gaining size. Yellow patches turn to brown as the disease advances.
Choose resistant varieties, which are widely available. Measures that reduce aphid populations will cut the risk of CMV and other viral diseases in the garden. Grow plenty of nectar-producing flowers to attract aphid predators including ladybeetles, lacewings and hover flies. If viral diseases are common in your garden, use row covers (garden fleece) to protect young spinach plants from aphids.
To keep aphids from spreading CMV to other plants in your garden, pull up infected spinach plants and compost them. If an entire planting is infected, also dispose of any unused seeds, because it is possible that the seeds were infected with the virus.