8 



berry becomes shrunken and dark brown. This form of the disease 

 is sometimes known as brown rot. Severe attacks cause much 

 shelling of the fruit. The disease is rarely seen on fruit on the market. 



Greenish-yellow irregular spots are produced on the upper surface 

 of the leaves, and a thin downy fungus growth develops on the under 

 side. Similar symptoms are produced on the young canes, leafstalks, 

 and tendrils, which are sometimes killed by the fungus. 



Spraying with bordeaux mixture seems to be the most effective 

 control measure 6 {17, 18, 26). 



FREEZING INJURY 



The native grapes of the eastern United States or varieties developed 

 from them, when injured by freezing, become shriveled because of 

 rapid evaporation from the skin, and usually show a milky, opaque 

 condition of the pulp. Normal uninjured pulp is greenish and semi- 

 transparent. When freezing injury is severe the grapes become so 

 watery and disintegrated that if the skin is broken all the material 

 inside, including the thin, pulpy layer on the inner side of the skin, 

 comes out leaving only a shell. Blue varieties undergo no color 

 change in the skin, but red or green varieties may show a slight 

 browning. 



Vinifera varieties when injured by freezing have a dull appearance 

 and are soft and flabby. They sometimes become wet and sticky. 

 The stems and cap stems are often injured by temperatures that 

 apparently have no effect on the berries. The frozen stems are at 

 first limp and pliable, with a water-soaked or dark-green appearance, 

 but they soon dry and become dark colored and are more susceptible 

 to mold invasion than sound stems. When berries, injured by freez- 

 ing, are pulled off the cap stem, the brush (the small bundle of fibers 

 that extends from the cap stem into the berry) is usually found to be 

 shorter than normal and somewhat browned. 



GRAY MOLD ROT 



(Botrytis spp.) 



OCCURRENCE, SYMPTOMS, AND EFFECTS 



The fungus known as gray mold has a wide distribution in nature 

 and attacks a great variety of fruits, among which are berries of all 

 kinds, grapes, oranges, lemons, peaches, apples, and pears. Grapes 

 affected with gray mold usually remain firm, and there is no marked 

 collapse of the tissues. The fungus usually forms a nest of rot, 

 spreading from an early affected berry to others surrounding it. The 

 berry from which the mold has spread can usually be found at the 

 center of the nest, well preserved in form but darkened and covered 

 with grayish-white mycelium. Sometimes berries scattered through 

 the bunch will be infected with gray mold, without any outward 

 evidence of the disease. If the bunch is shaken, berries will shatter, 

 pulling loose from the cap stem and leaving some of the flesh on it. 

 These berries, when held to a strong light, will have a brownish cast. 

 Probably the infection in such cases has taken place through the cap 

 stem, while the grapes were still on the vine. Grapes exposed to 

 several rains in the vineyard have shown this condition after several 



« Porter, B. A., and Demaree, J. B. See- footnote 3. 



