PLANT DISEASES 



257 



Bitter-rot (Fig. 131) is an example of a disease which 

 occurs on the fruit in one form, and on the wood in 

 another. This fungus, 

 when it gains access 

 to the wood, causes 

 a disease known as 

 bitter-rot canker. 



369. Damping-off 

 gives considerable 

 trouble especially in 

 the hotbed. The 

 young seedlings with- 

 er and fall over and FlG - isi.-Appie bitter-rot. 



an examination reveals that the stem has collapsed near the 

 point where it emerges from the ground. The disease spreads 



rapidly, and frequently 

 a large number of plants 

 are affected before it is 

 discovered. The condi- 

 tions which especially 

 favor its development 

 are moisture and 

 warmth. 



As the seedlings crowd 

 up out of the ground and 

 as the leaves develop 

 above, there is a space 

 between the ground and 

 the leaves where mois- 

 ture does not have a 

 chance to evaporate 

 and this makes an ideal 

 condition for the 



FIG. 132. Peach-yellows. 





development of fungus. When the hotbed is kept too warm, 

 a large number of plants may be lost in this way. Care must 



