22 MAXUAL OP FRUIT DISEASES 



difference in susceptibility. Under nursery conditions there 

 is evidence that the Yellow Transparent, Golden Russet, 

 Sutton, Fameuse, AVagener, Tompkins King, Rhode Island 

 and others are more affected than Ben Davis, Red Astrachan, 

 Oldenburg and Gravenstein. In New York and neighboring 

 states such varieties of the commercial orchard as Tompkins 

 King, Baldwin, Grimes, Alexander and others are susceptible. 

 In Virginia, the York Imperial and Grimes are most likely to 

 show fire-blight. In this and other regions one of the serious 

 troubles in connection with apple-growing is a form of fire- 

 blight known as collar-blight, collar-rot, or crown-rot. In 

 many cases this type of trouble is a form of winter-injury. 



Symptoms. 



Large cankers may be developed on the collar of bearing 

 trees, although these do not constitute the first noticeable signs 

 of the disease. The leaves appear yellowish and smaller on one 

 or more of the larger limbs, this effect developing gradually in 

 contrast to the sudden darkening of the foliage of twigs infected 

 with fire-blight. Premature defoliation is induced. The 

 canker is of variable size, depending on its age, and shows a 

 dark, sunken, smooth surface. Cankers in which the pathogene 

 is advancing do not exhibit a distinct margin as is the case with 

 older infections. The lesion develops until midsummer when 

 its growth is arrested, but is renewed the following season. 

 Ultimately complete girdling and death of the tree may result. 

 Usually the canker extends up the body of the tree into the 

 branches; it may also extend down into the lateral roots. 

 In case the collar-rot is due to weather conditions there is no 

 progressive dying as is found in this type of fire-blight. Fur- 

 thermore winter-injury is first seen at the beginning of the 

 growing season, whereas collar-blight is not observed until 

 midsummer. Fire-blight cankers are known to develop com- 

 monly at the base of water-sprouts about wounds of various 

 kinds on limbs and body. 



