How to Manage Pests
UC Pest Management Guidelines
Pathogen: Botrytis cinerea
(Reviewed 6/11, updated 6/11)
In this Guideline:
SYMPTOMS AND SIGNS
Gray mold infects flower parts at bloom time and remains quiescent until fruit ripening. Typically, once the fruit is washed or stored at high humidity, water or condensation on the blossom tissues activates the fungal mycelium to begin growing. The pathogen sporulates on the flower parts and the typical grayish coating of spores develops. Eventually the crown tissue will be colonized and the fungus will grow into the fruit tissue. Infected fruit held in storage at high humidity often completely decays and shows the typical gray coating of spores; it may also have grayish white mycelium and black sclerotia on the surface. Decay can also start from the stem end wound, especially if the stem is entirely removed.
COMMENTS ON THE DISEASE
Gray mold is one of the most important causes of postharvest decay in pomegranates.
Botrytis spores reside on previously infected plant tissue, weeds, and old fruit left on the tree or on the orchard floor. Spores are spread by wind. Spores landing on senescent flower tissues such as stamens (anther pollen sacks and filaments) germinate and produce an infection when there is free water on the plant surface from rain, dew, fog, or irrigation. Decay develops quickly when shelf temperature is about 65 to 75°F (18-24°C).
The extended flowering period of pomegranates makes bloom treatments for gray mold uneconomical and the fruit crown that covers the blossom prevents the use of preharvest sprays. However, postharvest treatments can be very effective.
Good orchard management practices, such as dust control and sanitation (removal of old fruit and dead branches), will reduce the postharvest incidence of disease.
Storing pomegranates properly can help avoid further decay by disease. The optimal postharvest storage temperature for pomegranates is 41°F (5°C) for up to two months and 45°F (7°C) for longer than two months. Store at 90 to 95% relative humidity. If storing for longer than three months, a controlled atmosphere of 5% oxygen plus 15% carbon dioxide is suggested.
UC IPM Pest Management Guidelines: