Garlic Plant Diseases

Possible Problems With Your Garlic Crop

Garlic is generally a very hardy crop which grows well in the garden, however there are a few diseases it is prone to. Many of these also attack onions, another allium to which garlic is closely related. I can’t cover everything here, nor can I diagnose individual cases, however I can give some idea of the sort of problems to look out for.

Treatment for these diseases depends on the sort of garlic grower – and general gardener – you are. Most of them can be treated by commercially available products. However if you prefer to use more natural, organic methods then crop rotation and careful selection of healthy seed is the usual recommendation.

The most commonly grown variety of garlic is allium sativum. This is divided into two main sub-varieties, hardneck garlic and softneck garlic.

  • Garlic Rot
    Rot is probably the most common garlic disease. There are two frequently encountered rots:

    • Basal Rot (Fusarium Oxysporum)
      Basal rot is a slow developing condition. Affected garlic plants show gradual yellowing and leaf dieback. There is sometimes a white fungal growth visible at the base of an infected bulb leading to the bulb rotting. Symptoms continue to get worse even after harvesting. Basal rot is favoured by higher temperatures and hence more common in warmer climates.
    • White Rot (Sclerotium Cepivorum)
      The symptoms of white rot are very similar to those of basal rot, however it attacks the growing garlic more quickly and is more likely to kill the plant outright. White rot prefers cooler temperatures. Dipping seed garlic in hot water before planting can reduce the chance of white rot but be careful: too high a temperature could kill the garlic itself.
  • Rust (Puccinia Porri)
    Rust first shows as leaf blotches of a reddish orange colour. If a plant is heavily infected then the leaves turn yellow and can collapse completely. Garlic plants infected by rust will produce a lower than usual yield and can produce deformed bulbs. Heavily infected plants can die.
  • Downy Mildew (Peronospora Destructor)
    Downy mildew can be recognised by an off-white, sometimes slightly purple, furry growth on the leaves of the garlic plant. The leaves go on to yellow then collapse. Since downy mildew is airborne, patterns of yellowing often follow prevailing wind directions in a large crop. Downy mildew can kill young plants and causes stunting in older ones.