Apple and Pear Disease - Blue Mold

Blue mold, a common rot of stored apples and pears, is caused by the fungus Penicillium expansum.
Apple and Pear Disease - Blue Mold - Articles

Updated:

Injuries to fruit, especially during picking and handling operations, are the primary points of entry. Photo by K. Peter

Blue mold is the most important postharvest disease of apples worldwide. Other names for the disease are soft rot, bin rot, and Penicillium rot. Aside from losses in fruit caused by rot, sound fruit in the same container as decaying fruit may absorb a moldy odor and flavor.

Symptoms

Soft rot appears as soft, light brown, watery spots that begin around injuries or lenticels on the outer surface of fruit. Rotted fruits have a characteristically moldy odor and flavor. When the relative humidity is high, grayish blue masses of spores may appear on the fruit surface.

Disease cycle

Spores of the soft rot fungus are present almost everywhere and can survive long periods of unfavorable conditions. Bulk bins, field crates, packhouse lines, and storage rooms are usually contaminated. Injuries to fruit, especially during picking and handling operations, are the primary points of entry. At ordinary temperatures, infected fruit can rot in 2 weeks or less.

Disease management, cultural

To control blue mold, it is important to prevent fruit from becoming injured during picking and handling.

It is also essential to move harvested fruit into cold storage as rapidly as possible. Packing line equipment and storage rooms should be cleaned and clean water maintained in water dumps and anti-scald solutions.

Disease management, chemical

Picking bins and boxes can be disinfected with fungicides or steam. Disinfectants or fungicides can be used in fruit dips and combined with wax applications.

Authors