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Ministry of Agriculture, Food and Rural Affairs

Rhizopus Rot

Rhizopus on a peach Rhizopus on a peach Rhizopus on a peach Rhizopus on a peach Rhizopus on a peach Rhizopus on a peach
Click to enlarge.

Beginner

This pest affects:

peach apricot plums sweet cherry    

Scientific Name
Rhizopus spp.

Identification
Fruit

  • Dime-sized lesions are cinnamon or chocolate-coloured
  • Skin slips readily from the underlying flesh
  • At warm temperatures, the fungus rapidly advances through the entire fruit
  • Initially fluffy white mycelial mass later turns dark gray to black as the fungus begins to sporulate
  • Watery rot
  • Seldom present in the orchard unless overripe fruit are left

Often Confused With
Early brown rot lesions- no slip-skin; skin is tough and leathery; can develop in the orchard as well as post-harvest

Period of Activity
Harvest- storage.

Scouting Notes
Rhizopus rot is more likely to be a problem where fruits are allowed to (over-ripen?) fully ripen on the tree. Monitor sanitary conditions of field bins or crates, the hydrocooler, and the packinghouse to reduce the incidence of this disease.

Threshold
N/A

Advanced

This pest affects:

   

Scientific Name
Rhizopus spp.

Identification
Fruit

  • Dime-sized lesions are cinnamon or chocolate-coloured
  • Skin slips readily from the underlying flesh
  • At warm temperatures, the fungus rapidly advances through the entire fruit.
  • Initially fluffy white mycelial mass later turns dark gray to black as the fungus begins to sporulate
  • Watery rot
  • Seldom present in the orchard unless overripe fruit are left

Often Confused With
Early brown rot lesions- no slip-skin; skin is tough and leathery; can develop in the orchard as well as post-harvest

Biology
Rhizopus is most common on peaches and nectarines. The fungus survives as thick-walled dark-coloured spores that can withstand long periods of cold and drying. These can be found in the remnants of rotted fruit in bins or on the orchard floor. Infection of fruit in the early stages of ripening requires injury from factors such as insects, hail or cracking for infection to occur. At harvest the skin is often injured at the stem. Rotted fruit on the orchard floor allow for inoculum buildup as the harvest season progresses. When infected fruit are held at 24-26ºC small spots of Rhizopus rot enlarge rapidly and can involve the entire fruit in 24 to 48 hours. A white, whiskery mould appears on the surface of infected fruits, spreading to nearby fruit and the walls of the container. Spread of the disease from fruit to fruit can occur without injury at the point of contact.  By this time, the fruit tends to leak and to smell like vinegar. Finally, tiny, black, spherical structures are produced on stalks above the white mold. Each of these contains thousands of spores that are released to float in the air. At this stage, the mould looks mostly black.

High temperatures and humidities favor the rapid growth of the fungus and the decay of the fruit. No spore germination or growth occurs at 4 °C.

Fruit picked and shipped to market becomes vulnerable to decay as the fruit ripens and sugar concentrations increase, especially if temperature during shipping is above 10ºC. One diseased peach in a container can infect many other fruits in a few days.

Period of Activity
Harvest- storage.

Scouting Notes
Rhizopus rot is more likely to be a problem where fruits are allowed to (over-ripen?) fully ripen on the tree. Monitor sanitary conditions of field bins or crates, the hydrocooler, and the packinghouse to reduce the incidence of this disease.

Threshold
N/A

Management Notes
Practice orchard sanitation and “soft handling” of fruit.  Avoid bruising and skin puncture when picking and transporting fruit.

Harvest fruit at proper maturity. Rhizopus tends to be a problem on overripe fruit.

Use clean bins. As much as practical, minimize the amount of soil and plant debris brought into the packinghouse on the bottom of bins.

Keep fruit cool after harvest, i.e. keep bins in the shade.

Minimize time between harvest and delivery of fruit to the packinghouse.

Store fruit at or below 4ºC.

Management with fungicides – Fungicides can be used to manage Rhizopus rot See OMAFRA Publication 360, Guide to Fruit Production:

Chapter 6 Peaches or Peach Calendar only: Recommendations for Rhizopus rot Postharvest fruit treatment.
Chapter 6 Apricots or Apricot Calendar only: Recommendations for Rhizopus rot Postharvest fruit treatment.
Chapter 6 Plums or Plum Calendar only: Recommendations for Rhizopus rot Postharvest fruit treatment.
Chapter 6 Sweet Cherries or Sweet Cherry Calendar only: Recommendations for Rhizopus rot Postharvest fruit treatment.

Some of the information above was excerpted from:

http://agsci.psu.edu/fphg/stone/diseases/rhizopus-rot-of-stone-fruit

http://www.agf.gov.bc.ca/cropprot/tfipm/rhizopus.htm