Market Diseases of Apples, Pears, and Quinces: Pink Mold Rot
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Pink mold rot
Pink mold rot

Pink mold rot
Pink mold rot

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Market Diseases of Apples, Pears, and Quinces
Pink Mold Rot
Cephalothecium roseum Cda.

Pink mold is no longer common on apples, because of improved handling practices and because the causal organism does not grow at cold storage temperatures. It is included in this publication because it occurs on apples held in a warm room for bull's-eye rot assay, and it may be confused with other diseases.

Formerly, pink mold was a problem in common storage. It was often associated with scab lesions and rarely penetrated the lenticels of sound fruits. In a warm room, however, most infections occur through lenticels. The first symptoms appear as small brown spots about 1/8 inch in diameter. As they increase in size, the spots are characterized by light centers and brown margins (top photo). On the rotted areas there is sometimes a growth of white fungus threads or, under warm, moist conditions, a pink mass made up of these threads and the pink spores they produce. If conditions are favorable, the second or final stage of the rot soon follows. This is characterized by chocolate-brown sunken areas of irregular outline, varying in diameter from 1/2 to 2 inches or even more. Scattered over these areas are depressed, circular spots which are lighter brown than the rotten area surrounding them. Under market conditions this late stage of the rot is less likely to show the white fungus threads and the pink spore masses than is the first stage. At any stage the rotted areas are rather firm and dry, or at least are not watery, and the affected tissues have a bitter taste.

Superficially pink mold rot resembles fish-eye and bull's-eye rots. Spots of pink mold rot can generally be distinguished by their irregular shape and by a white to pinkish growth of mold. The fungus is a shallow-growing organism, penetrating the flesh about 1/8 inch. Fish-eye and bull's-eye rots usually produce round or elliptical lesions, with the decay extending into the deeper tissues of the fruit. In fish-eye rot, the decayed tissues are tough and stringy, and a growth of white cobweb-like fungus may develop on the surface of the fruits. In bull's-eye rot, the decayed tissues are less firm, with a mealy texture. Below 50 °F, pink mold develops very slowly and is not at all likely to start at new places; at 32 °F it is checked almost entirely. Control is therefore best obtained by means of refrigeration. Infection rarely spreads from one fruit to another unless the fruits are held at fairly high temperatures for some time after harvest.

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Monday, September 19, 2005