CHAPTER IX 



PHYSIOLOGICAL DISEASES 



Physiological diseases are those dis- 

 turbances of the normal activity of a plant 

 which are not induced by fungi, bacteria, 

 or insects. 



Bud Drop. The young flower buds at a 

 very early age, turns yellow and drops o£E. 

 This disease is sometimes confused with 

 the drop produced by the anthracnose dis- 

 ease. In the latter case the flower develops 

 into a normal spike, but it is attacked soon 

 by the fungus, Glomerella rufomaculans, 

 which girdles it at the point of attachment 

 between the flower and the peduncle. In 

 this case the blossom falls off, leaving be- 

 hind the beheaded peduncle. In bud drop, 



i8i 



