Chalara - Black Root Rot

Chalara is a serious nursery pathogen which is frequently encountered in Australia. Given that chlamydospores of the disease can very abundant on the roots of the plants that appeared healthy above ground, great care needs to be taken to remove this disease from the nursery; infected plants cannot be cured. Chalara is a soil borne pathogen which can be a major seedling disease of a large number of species.

  • Remove all affected plants hygienically, e.g. into a skip for deep burial – close the lid.
  • Do not leave infected plants in a throw-out pile on site.
  • Since the spores can be spread by wind or rain/irrigation splash, it is highly recommended to carefully examine the roots of healthy plants that were grown adjacent to diseased plants.
  • If any symptoms exist, these plants should also be removed, as above.
  • Alternatively, a selection of plants that were grown close to infected plants could be sent to a diagnostic laboratory to determine if Chalara was present in the roots.

Once you remove all infected plants, it is worthwhile treating with an appropriate fungicide to limit infection of healthy plants that may come into contact with Chalara spores that are inevitably present in the growing area, including benches and the ground. The only active ingredients registered against Chalara on ornamentals are thiophanate-methyl with etridiazole (e.g. Banrot).