DISEASES OF PLANTS— SPRAYING 



233 



the pupils bring some oats in a sack, and treat them in a 

 pail of water with a httle formahn in it. 



Exercise. — Showing Grain Smut. — Perhaps sample heads 

 of diseased grain can be brought to school. If so, preserve 

 them as shown in Fig. 148. Some one should bring samples 

 of corn smut disease to show to the class. Corn smut is not 

 prevented by the formalin treatment. 



Exercise. — Treating Seed Potatoes. — The pupils may- 

 bring a pail and a few potatoes from home. A half- 

 ounce (four teaspoonfuls) of formalin should be added to 



Fig. 149. — Spraying orchard trees in early spring, for scale insects, with barrel pump. 

 (Experiment Station, N. J.) 



one gallon of water. Soak the potatoes in this mixture 

 for two hours. Urge the pupils to tell of the method 

 at their homes. 



Spraying. — Under ordinary conditions a bearing apple 

 orchard should be sprayed at least three times each spring 

 and perhaps once in the summer. 



The first spraying is to be made before the buds swell in 

 very early spring (Fig. 149). This is to prevent scab and 

 similar diseases and to kill the San Jose scale insects. For 

 this spraying it is well to use either soluble oil at the rate of 

 one gallon of the oil to fifteen gallons of water, or to use the 



