Postharvest Diseases of Cherries
Alternaria rot (Alternaria spp.) is dark brown to black, firm, and slightly moist. The affected area appears as a spot on the surface of the fruit and may be covered with olive-green spores and white strands of mold. The rotted tissue can be readily separated from the surrounding flesh. The fungus is widespread in nature, entering the fruit through cracks or wounds. There are no effective chemical controls but suppression has been reported with Rovral 50W. Hold fruit as close to 32°F as possible. Alternaria rot has been reduced by storage in modified atmospheres at 10% CO2.
Blue mold rot (Penicillium expansum LK. ex. Thom.) first appears as a circular, flat, light brown area. The affected tissue is soft and watery. As the rot develops, the skin cracks to reveal small, white tufts of mold. Under humid conditions the mold grows, producing a crop of bluish-green spores. It is particularly common in fruit that has been exposed to rainfall or high moisture conditions. Susceptibility increases as the fruit matures.
Cladosporium rot (Cladosporium herbarum) is widespread in orchards but enters the fruit only through breaks in the skin. The decayed tissue is hard, dry, gray to black and the rotted area is easily separated from the flesh. Careful handling, removal of damaged fruit and rapid cooling are the only effective management tools
Gray mold rot (Botrytis cinerea Pers. ex Fr.) first appears as a light-brown spot on the skin. As the fungus grows, the underlying flesh becomes watery and dark brown. Under dry conditions, gray spores are produced abundantly; under moist conditions, such as in a cherry box, an abundant white growth of fungus may cover affected fruits.
Rhizopus rot (Rhizopus spp.) is one of the most serious postharvest diseases of cherries. Infection usually occurs after harvest and enters the fruit through cuts, cracks or bruises. The fungus will not develop below 45°F and can be controlled by holding the cherries as close to 32°F as possible.
Preharvest Practices to Minimize Decay
- Apply mildew fungicides according to
- Shield harvested fruit from sun and heat as much
- Minimize exposure of picked fruit to dead plant material (leaves, twigs, sticks, grass, etc.) and dust. Place picked cherries in clean, dry lugs or bins.
Postharvest Practices to Retain Quality
- Hydrocooling cherries removes field heat,
contributes to longer shelf life and provides the first
opportunity to clean the fruit and remove fungal spores
that can cause infection and decay in storage.
- Hydrocool cherries as soon after harvest as is
- Eliminate soil adhering to bin skids, as this can
be a source of Penicillium, Mucor and
- When outside hydrocoolers are used, 2.0-3.0 ppm
chlorine dioxide combined with a low foaming, ethoxylated
linear alcohol surfactant (and antifoam agent if
should be used. This maintains green stem color during
subsequent storage and will clean and partially disinfect
the fruit of field-borne fungal spores. Chlorine dioxide
treatment should be followed by potable water rinse. When
hydrocoolers are located indoors, use no more than 100 ppm
free chlorine with a surfactant instead of chlorine
dioxide. The pH of hydrocooler water after addition of
hypochlorite should be 7.0-8.0 for maximum antimicrobial
activity. Free chlorine levels should be monitored hourly
- For Lambert and Rainier cherries, treat with a
chlorine dioxide or chlorine/surfactant dip or drench
followed by fresh water rinse. An automated system for
monitoring and control of free chlorine levels directly or
by pH is highly recommended. This will minimize chlorine
level fluctuations over time and will increase the
effectiveness of the chlorine treatment.
- After hydrocooling or chlorine immersion
store fruit as close to 32°F as possible until run on
- Fruit should receive potable water rinse after any
chlorine or oxychlorine treatment.
- The importance of good sanitation cannot be
overemphasized. Fruit otherwise handled properly to
decay can become reinfected with fungal spores from
packingline equipment if the equipment is not kept
- Remove all damaged, crushed or otherwise
fruit from packinghouse floors, belts, pulleys and any
surface that comes in contact with fruit.
- Periodically clean all equipment in contact with
fruit with a detergent, then sanitize with a surface
sanitizer approved for food handling surfaces.
- Thoroughly cull all split, crushed or otherwise
damaged fruit at the earliest possible step during cherry
- Do not store culled fruit in the same room with
- Treat fruit as soon after harvest as practical.
Follow recommended practices and precautions for all
- Captan 50W 2.5 lbs./100 gallons or Captan 80W at
1.6 lbs/100 gallons. Apply as dip or drench; recharge
suspension when water volume in tank is reduced by 25%;
1.0 lb. of Captan 50W or 5/8 lb. of Captan 80W per 25
gallons water added. Dump tank at the end of every 8-hour
- Rovral 50W 2.0 lbs./100 gallons. Will also suppress Rhizopus spp. and Alternaria, according to tests done in California; apply as a line spray or dip treatment.
Dr. Eugene Kupferman, Postharvest Specialist
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Tree Fruit Postharvest Journal 4(1):22-24