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Onions and related crops in Ontario are susceptible to a variety of diseases and conditions. Most diseases are caused by fungi or bacteria of .

While ailments can be attributed to bad weather, air pollutants, soil conditions, nutritional imbalance and pesticides. Sometimes several illnesses and conditions occur at the same time.

It is important to know how to recognize onion diseases at the first symptoms in order to be able to adopt effective management strategies. 

The culture allows you to be alerted in time?

The field and past crops can provide excellent clues to the risk of disease and disease, because while some diseases may arise at any time unpredictably, others return year after year. 

  • A soil analysis revealing its pH, salinity and nutrient content can also be very useful.
  • Smut is caused by Urocystis cepulae , a soil-borne fungus that infects the whip (cotyledon) upon emergence. It is not uncommon for seedlings to survive .

This initial infection, but leaves and young bulbs subsequently show characteristic black blisters and streaks as the fungus moves onto the new leaves ( Figure 1 ).).

It is to be expected almost every year that this disease will cause the death of some seedlings. Wet, cold weather in the spring increases the incidence of smut since the seedlings are then slower to emerge and the whip stays longer in the soil. 

For the same reason, seeds buried too deeply are more susceptible to this infection. Spores of the smut fungus survive in the soil for many years, and even multi-year rotations fail to reduce the incidence of the disease. 

To mitigate losses, treated seed can be used. On the other hand, to avoid the disease, it is preferable to resort to transplanting plants.

Seedlings are susceptible to a number of common ailments including leaf tip dieback, stunted or stunted growth, uneven emergence and physical injury.