Affected plants can appear until harvest. A progressive decay occurs in the bulb as secondary bacteria enter and as maggots become attracted to and feed within affected tissues. If infections occurred late in the season, this decay may not be apparent until after storage. Its life cycle from egg through larval stages to egg laying occurs in 19 to 25 days. High populations can contribute to damping-off.
Seedlings become pale green to yellow, twisted and arched when infected.
Young bulbs are soft, swollen and misshapen, and exhibit a coarse-textured tissue beneath the outer scale. Small yellow spots, swellings or open lesions may appear on leaves of stunted plants, and leaf tips often exhibit a gray to brown dieback. Stems and necks are often softened, a high incidence of doubles or cracked bulbs and culls occurs, and secondary invaders usually rot the bulbs before or during storage. Disease Management Soil-borne problems of onions are managed, but not eliminated, by using carefully implemented integrated approaches to crop production and protection. These approaches reduce disease pressure and plant stress, thereby enabling vigorous plants to compete more successfully for nutrients and moisture during plant and bulb development.