MARKET DISEASES OF FRUITS AND VEGETABLES 35 



where in some years it may affect 50 to 90 percent of the fruit. 

 In some years it has been important in New Jersey. This disease 

 occurs also in Canada and has recently been reported in Germany 

 and southern Africa. Varieties most seriously affected are Bald- 

 win, Jonathan, Rome Beauty, Tolman Sweet, Grimes Golden, and 

 Stayman. Many others have been reported as susceptible. 



The spots are % to *4 mc h in diameter and deep red or black 

 on red areas and dark green on green or yellow ones (pi. 1, 

 G, H). Late in the fall or after the apples are in storage the 

 central part of the spot becomes flecked with black, which can be 

 observed more readily by removing the surface of the spot by 

 making the thinnest possible paring. There will then be seen in 

 the flesh underneath a number of very small brown or black 

 specks, which are aggregates of cells killed by the fungus. These 

 specks can sometimes be seen through the cuticle but are more 

 likely then to be obscured by the surface discoloration. Owing to 

 the collapse of the cells in the affected area, the larger fruit spots 

 become slightly sunken. On overripe apples the spots are often 

 surrounded by a band of brown. 



Because of their speckled appearance, fruit spots caused by 

 Mycosphaerella are easily distinguished from all other spot dis- 

 eases of apples. They are further distinguished from bitter pit 

 by not being markedly sunken except in later stages, by occurring 

 only in the epidermis of the fruit, and by having no connection 

 with the water-conducting system. 



On fruit in cold storage the spots change but little. In delayed 

 storage or in transit new spots may appear and older ones may 

 seem to enlarge slightly. In the main the seeming enlargement 

 results from the change in color of the fruit rather than from 

 actual enlargement of the affected areas. 



CONTROL MEASURES 



Infections on the fruit appear not earlier than June and may 

 continue until August. The disease can be controlled by spraying 

 in accordance with the recommendations of the local agricultural 

 experiment station. 



(See 10, 12, 59, 65, lib, 132.) 



Gray Mold Rot 

 (Botrytis spp.) 



CAUSE, OCCURRENCE, AND SYMPTOMS 



More than one species of Botrytis has been reported as causing 

 a decay of apples known as gray mold rot. The most common 

 species is Botrytis cinerea Fr. Gray mold rot occurs on apples 

 grown in the Pacific Northwest and in various producing sections 

 in the eastern United States. It is not common and is seldom as 

 destructive on apples as on pears grown in the Pacific Coast 

 States. In the Northwest the Winesap variety seems to be 

 affected more often than any other. Gray mold is second to blue 

 mold in losses it causes in storage and handling of eastern apples. 



Gray mold rot developed in cold storage is characterized by 

 diseased areas that at first have a pale, translucent, watery ap- 

 pearance and remain light brown to brown. The spots are firm 

 at first but become soft as the rot advances (pi. 6, F-H). Fre- 



