The downy mildew pathogen overwinters in infected crop residue and in soil as resistant spore-structures. It is also possible for the pathogen to be carried with the seed. Infection and spore production will continue throughout spring and early summer as long as favorable conditions persist. Disease Control . In growing regions where downy mildew is an annual threat to production, farmers rely on fungicides to reduce losses caused by mildew.
Protective fungicides provide a moderate degree of control.
If downy mildew is already established in a field, a systemic fungicide can be used to eradicate existing infections. Neck Rot Introduction Neck rot is a common postharvest disease that is destructive to onions in transit or in storage. Damage can be severe in onions not cured or stored properly. The disease is caused by the fungus Botrytis allii . Neck rot symptoms are marked by sunken, collapsed tissues around the neck of the onion bulb.