356 CONTROLLING INSECTS AND DISEASES 



nor the flat-headed and round-headed apple tree borers can be 

 controlled by spraying or dusting the tree. 



Eall and early spring plowing destroys many larvae of the 

 Oriental fruit moth and aids in scab control by turning under 

 the old leaves from which the first infection comes in the 

 spring. The use of parasites, especially macrocentrus, to con- 

 trol Oriental fruit moth is to be considered. 



(N. Y.'Geneva Exp. Station) 



Fig. 137. Fruiting bodies (perithecia) of apple 

 scab on an overwintered apple leaf from which 

 spores will be discharged during spring rains. 



Fire blight of the apple, pear, and quince, a bacterial dis- 

 ease, does not yield to the spraying or dusting program and 

 must be fought by different methods. 



Fertilization and special stimulative treatment, including 

 cultivation of affected trees, are sometimes advisable. By in- 

 creasing their vigor their resistance is increased and their recu- 

 peration is hastened. This method is employed often in cases 

 of extreme defoliation of the trees in the growing season and 



