10 MISC. PUBLICATION 3 4 0, XT. S. DEPT. OF AGRICULTURE 



in transit, or from shifting and breakage due to improper stowing of 

 the packages. While there is danger of loss from gray mold rot even 

 when injuries are few, since the fungus is able to penetrate the un- 

 injured skin of most fruits, the danger is much greater if injuries are 

 numerous. A product that has suffered from careless handling of 

 any sort is much more subject to attack than one that has been 

 carefully handled at every step. 



Temperature is also of definite and direct significance. Gray 

 mold rot develops fairly fast in the field during cool weather; in 

 transit and storage its growth is not entirely checked by the tempera- 

 tures ordinarily found in refrigerator cars. It is in fact able to grow 

 and cause some decay at 32° F., although its progress at that tempera- 

 ture is much slower than at higher ones. Growth of the fungus is 

 most rapid at about 77° and falls off as the temperature is raised 

 above that point, the rate of decrease being greatest above 86°. 



CONTROL MEASURES 



Control of gray mold rot in transit depends on careful handling 

 methods, good refrigeration (40° to 45° F.), and prompt movement 

 of all shipments from field to market. For control in storage the 

 temperature should not be higher than 32° and for storage varieties 

 of grapes might well be 1° or 2° lower, since the freezing point of these 

 varieties averages about 25°, varying considerably with the sugar 

 content. Fumigation with sulphur dioxide is desirable. 



Pruning and trellising methods that permit the grapes to dry rapidly 

 after rain or foggy weather will probably be helpful in reducing infec- 

 tion of the fruit in the vineyard (7, 9, 12, 32, 47). 



GREEN MOLD ROT 



(Species of Cladosporium, Alternaria, and Hormodendrum) 



On grapes of the Emperor and other storage varieties held in cold 

 storage for 3 or 4 months, a black firm decay involving one side of the 

 berry is occasionally found. The decay is not definitely sunken, but 

 the grape is flattened or wrinkled on the affected side. The surface 

 of the lesion is usually smooth and unbroken, although occasionally 

 it is covered with a sparse growth of gray-green fungus. The decay 

 is shallow, usually not extending to the seeds. The affected tissue is 

 firmly attached to the skin and can be easily removed with it. It is 

 dark and firm in the center, becoming milky and gelatinous toward 

 the edges. 



Nothing is known concerning factors influencing the decay. Prob- 

 ably the organisms causing it gain entrance through injuries received 

 during harvesting or fumigation. It develops slowly at a storage 

 temperature of 32° F. 



HAIL INJURY 



Grapes that have been torn by hail are of course easily recognized 

 if examined a day or two after the injury occurred. There is, how- 

 ever, another form of the injury that may at times be confused with 

 internal browning (p. 11). This occurs when grapes are bruised 

 by hailstones but in such a way that the skin is not broken. It is 

 characterized by a browning of the flesh on one side of the fruit in- 

 stead of in a zone completely surrounding the seeds, as in internal 



