Onion Botrytis Information: What causes crown rot in onions?

Onion neck rot is a serious disease that most often affects onions after harvest. The disease makes the onions soft and waterlogged, which damages the onions themselves and also paves the way for other diseases and fungi that can enter and decompose the onions. Read on to learn more about identifying and treating onions with neck rot.

Symptoms of neck rot in onions

Onion neck rot is a disease caused by a particular fungus, Botrytis allii . This fungus affects alliums such as garlic, leeks, onions and spring onions. It is often only identified after harvest, when onions are damaged during transport or are not properly dried before storage.

First, the tissue around the neck of the onion (the top, facing the foliage) is soaked in water and runs. The tissue may turn yellow and a grey mold spreads in the layers of the onion itself. The neck area may dry out, but the flesh of the onion becomes soft and rots.

Black sclerotia (the hibernation form of the fungus) will develop around the neck. Wounds caused by onion botrytis also open the tissue to infection by a number of other pathogens.

Prevention and treatment of onion neck rot

The best way to prevent onion neck rot after harvest is to handle onions carefully to minimize damage and treat them properly.

Let half of the leaves brown before harvesting, let them dry in a dry place for 6 to 10 days, then store them until ready to use in a dry environment just above freezing.

In the field or garden, plant only disease-free seeds. Space the plants about one foot apart and wait three years before planting onions in the same spot. Do not apply nitrogen fertilizer after the first two months of growth.