DISEASES OF PLANTS SPRAYING 



255 



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

 of water with a little formalin 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 one gallon 



FIG. 149. Spraying orchard trees in early spring, for scale insects, with barrel 

 pump. (Experiment Station, N.J.) 



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 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 



