This disease is caused by the aster yellow phytoplasma which affects many weeds and crops including onions, carrots, lettuce and celery. The pathogen is transmitted by the aster leafhopper (Macrosteles quadrilineatus Forbes). Symptoms initially appear as a yellowing at the base of young leaves, which then spread toward the top. Leaves flatten, become marked with green and yellow streaks, but do not twist. Flower stems are abnormally elongated, and have malformed, sterile floral clusters.
Disease management recommendations include crop rotation out of onions for three years; elimination of weed hosts in and around onion fields; insect control; and isolation from other susceptible crops or volunteer onions.
Categories: Onion, Aster yellows, Mycoplasma, Diseases
Date: 04/01/2007