Neck rot symptoms are marked by sunken, collapsed tissues around the neck of the onion bulb. Infected necks soon appear dried out, and a gray mold often occurs between the scales on the collapsed areas. Infection by the neck rot fungus often is followed by a watery soft-rot of the bulb. Disease Cycle . During the spring and summer, sclerotia produce spores which are released into the air during moist weather.
Successful infections occur only where spores land on cut or wounded areas of onion tissue.
Disease Control . Fungicide sprays for other diseases should be discontinued once bulbs have reached full size. At harvest, tops should be cut close to the bulb. Onion Smut Introduction Onion smut is a disease common to temperate growing regions, especially where onions are grown from seed. Most onions and related crops are susceptible to smut.