188 MANUAL OF FRUIT DISEASES 



WlTCHES'-BROOM 

 Caused by Exoascus Cerasi (Fckl.) Sadeb. 



Witches'-broom is a peculiar type of gall in which there is- 

 an over-production of whole organs, resulting in a broom, or 

 nest-like habit of growth. This name is in general use in North 

 America. In England, the disease is called thunder-bushes, 

 bull-boughs, bull-wood and bull-branch. The Germans refer 

 to it under the name Hexenbesen, while, the French call it 

 Balai du Sorciere. 



The disease is very common and destructive in Europe, where 

 both sweet and sour cherries are affected. Although the 

 English sweet cherry (Prunus avium) is commonly cultivated in 

 eastern United States, the disease was not recorded until 1886, 

 when it was reported from Germantown, Pennsylvania. About 

 ten years later it was found in Long Island at scattering points. 

 The witches'-broom disease of cherry is not a disease well- 

 known to American cherry-growers. It occurs sparingly in 

 New York, but is said to be common in Oregon. It has also 

 been observed in a few other states, including Washington, 

 Minnesota, Pennsylvania and New Jersey. The disease is 

 of most interest perhaps because of the fact that the pathogene 

 spreads so slowly, and on account of the peculiar effect on the 

 cherry. Its history thus far in this country does not indicate 

 that the disease should ever be feared by cherry-growers. 

 Records show that the disease may affect in this country the 

 following cherries : English sweet cherry (Prunus avium), 

 sour cherry (Prunus Cerasus), wild black cherry (Prunus 

 serotina), wild red cherry (Prunus pennsylvanica) , choke-cherry 

 (Prunus virginiana). Several varieties and species of plums 

 are also affected. 



Symptoms. 



The twigs and leaves are susceptible to this disease. On the 

 former it produces a very striking deformity, although not a 



