Coprinus Rot, Snow Mold Rot

Coprinus Rot (Snow Mold Rot)

This rot of stored apples and pears has been a serious problem on Spartan and Golden Delicious apples. It is caused by a fungus which grows at temperatures near 0°C and can tolerate controlled atmosphere (CA) conditions. Plants such as grass, alfalfa and clover can serve as sources of infection for Coprinus rot in orchards.

Coprinus rot generally doesn't appear on stored fruit until March. Early symptoms of this rot are similar to Bulls-eye rot. Both storage rots will cause stem end or calyx end decay as well as circular rots centered at a lenticel or puncture. The circular rot caused by Coprinus rot is brown with a pale yellow center. Advanced stages of infection appear as masses of white fungus growth covering the fruit. Coprinus rot is also known to cause an internal brown decay of apples around the core with no symptoms on the outside of the fruit.

coprinus rot Coprinus rot on apple.
Photo courtesy of Dr. P.L. Sholberg, Agriculture & Agri-Food Canada

Cultural Control

Pick fruit at optimum maturity.
Handle fruit carefully to prevent punctures and bruising.
Make sure that orchard litter such as grass or weeds from the orchard floor does not get into the bin during harvest. Fruit picked off the ground must be placed in the cull bin.

Chemical Control

No chemicals are registered for control of this disease. Laboratory studies have shown that Nova and Nustar are very effective in reducing the incidence of this rot in apples.

February 2004

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