Soft rot can cause significant losses in stored onions. It is spread by splashing rain and by mechanical or insect damage. The bulb is infected through neck tissue of maturing plants.
Spray a copper soap fungicide on plants when warm, wet/humid conditions prevail, right up to time of harvest. Allow onion tops to dry before storing. Avoid bruising bulbs and store onions only after they have been well dried. We recommend Soap-Shield Flowable Liquid Copper Fungicide.