54^ DlE-i>ACK OF APPLE TREES. 



gradual killing is less frequent. Infections on older Ijranches 

 during the winter months produce oljlong wounds extending up 

 and down the stem. The lips of the bark formed over these 

 wounds do not meet, leaving scars, and in very severe cases 

 where there is a constant enlargement about the point of injury 

 rough, black, barrel-shaped enlargements are produced. The 

 disease also causes large cankers and so-called sun-scald wounds 

 on the trunk and larger limbs, and in cases large limbs and even 

 whole trees in ditierent states of vegetation and at different 

 times of the year die suddenly. The foliage of limbs or trees, 

 which die suddenly late in the spring and summer, takes on an 

 unhealthy, starved appearance, and wilts suddenly. The leaves 

 of those that will die in the following winter in most cases also 

 take on a yellowish colour and fall prematurely. 



The author also cites a number of inoculation experiments 

 on peach and plum trees, which leads to the conclusion that 

 Cytospora rubescens Nitschke is the conidial form of Valsa 

 Icucostoma Pers. The pustules of these two forms he constantly 

 found intermingled on limbs and trunks, but on the branches 

 only the Cytospora form. Inoculations with Valsa spores pro- 

 luced wounds on which developed the Cytospora form. 



Rolfs (5), in a later publication, mentions that the hyphae 

 of Cytospora cincta are usually found associated with a condi- 

 tion in peach trees frequently referred to as winter killing, 

 cankers of the limbs and sun-scald of the limbs and trunk. The 

 perithecial stromata he found abundantly on the limbs and 

 trunks, whereas pycnidial stromata develop freely on the twigs 

 and branches, and also occur on the trunks and larger limbs. 

 Cultures of the fungus were obtained from cultivated cherries, 

 wild cherry, peach and plum trees, and it is claimed that there 

 are sufficient variations to warrant the formation of two distinct 

 varieties, viz., V. Icucostoma cincta n.var. on cultivated and wild 

 cherry and peach, and V. leiicostoma nibesccns n.var. on the 

 apricot and plum. 



Wormald (6) describes Cytospora Icucostoma on young 

 bearing cherry trees at Wye, where in 1910 it caused the death 

 of a large number of trees. Affected trees are described as show- 

 ing a general yellowing and wilting, commencing at the tips of 

 the shoots. The leaves begin to wither in May, and the whole 

 of the upper part of the tree is dead bv October. 



Cytospora has been detected on the following fruit trees in 

 South Africa : — 



Apple, Maclear, C.P., February 26th, 1912. 



Apricot and plum, Swinburne, O.F.S., May 17th, 1912. 



Apple, Great Brak River, C.P., November 14th. 1912. 



Apple, Pietersburg, Transvaal, February 17th, 1913. 



Apple, Muiden, Natal, April ist, 191 4. 



Apple, Swinburne, O.F.S., August 8th, 1914. 



Peach, Pretoria, Transvaal, March 23rd, 191 5. 



