Signs of Spinach Aster Yellows
Spinach that is yellowed and stunted may have Aster yellows. This common disease causes foliar damage, and in crops grown for their foliage, such as spinach, the effects can be devastating. Aster yellows on spinach is transmitted by an insect vector. The disease has a symbiotic relationship with the insect, who overwinters it and incubates it until it has multiplied. In spinach, the foliage becomes faded and yellow. Young plants that get the disease will be stunted, narrow, and may form rosettes. Oldest leaves may develop some red to purple coloring on the edges. Inner leaves are stunted and may exhibit brown spots. Because spinach is cropped for its foliage, it and other greens are most severely affected. The leaf veins in some cases become clear, especially in newest growth. The flavor and appearance of the leaves becomes unpalatable and the plant must be thrown away. They should not be consigned to the compost bin, as the disease can possibly survive and re-infect the garden if used.
Causes of Aster Yellows of Spinach
While the primary method of dispersal comes from an insect, the disease can overwinter in host plants too. Common hosts include:
Thistles Dandelion Wild chicory Wild lettuce Plantain Cinquefoil
The insect vector is the leafhopper. They ingest the bacterium-like phytoplasma while sucking plant sap. There is a latent period of two weeks where the insect cannot transmit the disease because it is incubating inside the leafhopper. Once the disease has multiplied, it moves to the insect’s salivary glands where it can be transmitted to other plants. After that it takes another 10 days or so before aster yellows on spinach is evident.
Treating Spinach with Aster Yellows
Unfortunately, control is not possible, so the focus must be on prevention. Keep weed hosts out of the garden. Destroy any infected plants. Grow spinach under cloth to prevent leafhoppers from feeding on the plants. If plants are purchased, inspect them carefully before installing them in the garden. Avoid planting other susceptible plants near the spinach crop. Do not plant spinach in soil where a previously infected species was housed. Some gardeners suggest mulching with thin strips of aluminum foil around the plants. Apparently the leafhoppers are confused by the bright, reflected light and will dine elsewhere.
