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Mucor rot (Mucor piriformis)

Mucor rot on Bramley

Mucor rot causes losses at low levels in stored fruit in most seasons, but occasionally causes significant losses  in some fruit consignments.

It is a wound rot, invading fruit through damage.

The disease produces symptoms of a pale to mid-brown, very soft wet rot.  

  • Rapid softening of the tissues occurs leading to a slimy disintegration of the flesh. 
  • Although the skin remains present it is very weak and collapses under the slightest pressure.
  • A profuse growth of white coarse mycelium bearing black pin-shaped spore heads may be present.

The life cycle and epidemiology of this soil-borne fungus results in fruit becoming infected through contamination with soil during wet harvests, or from contaminated drench tank water.

Inspection of fallen fruit prior to harvest may identify high levels of Mucor rotted fruit and alert the grower to the need for good hygiene at harvest.  However, no forecasting systems have been developed for Mucor.

Bare earth orchards are likely to have a greater risk of Mucor rot.

Control

  • There are no chemical treatments effective against Mucor rot although treatment of water with chlorine has been shown to have some effect.
  • Control or prevention of Mucor rot is therefore dependent on cultural measures based on good hygiene and careful picking at harvest and avoiding soil contamination of bins.  These measures apply equally to organic and conventional orchards.

Control in organic orchards