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FRUIT PESTS 



Black Knot. The large black swellings that are fre- 

 quently seen on the branches of the plums and sour cherries 

 are caused by the black-knot disease. It attacks the 

 young twigs first and works its way down into the larger 

 branches, finally killing the tree, if not controlled. 



To control this disease, remove all infected limbs by cut- 

 ting several inches below the knot, and then burn. Paint all 



Fig. 150. Development of black knot on young branches. 



large wounds made in removing infected branches. Spray 

 the trees as directed for brown rot, and remove all wild 

 cherry trees and neglected plum trees about the garden. 

 It is not a serious disease, if controlled. Every spring 

 the trees should be carefully examined and all infected 

 branches cut out. 



Bacterial Diseases. Some of the most serious diseases 

 of fruits are caused by bacteria. Fire blight, a common 

 disease of pears, apples, and quinces, is a familiar example. 

 Although we cannot cure or prevent these diseases by 

 spraying, because they work entirely within the plant, we 

 can generally control them by various means which will 

 be considered later. 



Fire Blight. - Fire blight is a serious bacterial disease 

 of pears, quinces, and apples. The bacteria work within 



