LESSONS OlSr POTATOES FOR RUKAL SCHOOLS. 21 



E. Notes on spraying: 



1. It pays to spray. It is economical to use a combination spray, a poison 



and Bordeaux. 



2. Application should be timely and thorough ; all the vines need to be 



well covered. 



3. Do not wait until the plant disease begins to show among the vines. 



Anticipate its coming and spray before it arrives. 



4. Do the work in season. Do not wait until it is too late. Once the 



blight gets a start in the potato field, it is very difficult to control. 



5. Do not buy too cheap a machine. Get a good one and save time, 



trouble, and expense. 



6. Be sure that the material is properly prepared. 



Practical exercises. — This lesson should be made essentially a lesson 

 of practice. Whenever practical, specimens of the insect pests should 

 be brought to the class and identified. The treatment for such should 

 be understood. In a like manner specimens of diseased potato plants 

 and tubers should be studied. Pupils should be taught at least to 

 identify the blights and scabs. The methods for control of each 

 should be discussed carefully. Since the Bordeaux mixture for dis- 

 eases and the arsenic poison for insects are the common sprays, the 

 advantage of the combination spray should be shown. Actual prac- 

 tice work in preparation of these sprays and in their application 

 should be given. Visit a potato farm and observe the spraying 

 methods. If deemed practical, allow the class to assist in the spray- 

 ing. By using borrowed sprayers and water in place of spray 

 solution, actual practice may be given the class in the handling of 

 sprayers and in the method of applying the spray. Instruct the 

 class to be on the outlook for signs of potato diseases and insect pests, 

 and have same reported to the class and a study made at once. To 

 summarize: Give plenty of practice in identification of insect pests 

 and diseases, practice in preparation and use of sprays, and drill in 

 the general control methods outside of spraying. If any one of the 

 students has a potato project, he can apply the principles of this 

 lesson to his own crop. 



Correlations. — Spraying costs compared with additional yield and 

 losses incurred where no spraying is done; comparative cost of 

 spraying with other costs of production will give practice work 

 in arithmetic. The formulas for spray mixtures will also give 

 additional practice. 



Eeports on observations and practice work will give language 

 material and the preparation of spray charts and formulas will af- 

 ford work in drawing. 



LESSON XII. 



Sudject. — ^Uses of the potato — The potato as a food. 



ProhleTn. — To study composition, food value, and uses of the potato. 



