PLANT DISEASES 43 



Practical Exercises 



1. Observation of Some Plant Diseases 

 Bring samples of diseased plants to the school and 



fill out the following outline as you study the speci- 

 mens: 



2. Treating Oats for Smut 



Bring a half bushel of oats to school in a "gunny- 

 sack." Soak the oats, sack and all, for about ten 

 minutes in a vessel holding ten gallons of water, to 

 which has been added one-fourth pint of formaldehyde 

 (40 per cent). Then spread the oats out to dry. The 

 formaldehyde kills the spores of the smut that are on 

 the oats, and the crop coming from this treated seed 

 will be free from the disease. It would be a good 



service to the farmers if the school would treat all the 



* 



seed oats in the community. 



Problems 



1. Suppose it takes 200 gallons of Bordeaux mixture 

 to spray an acre of potatoes. What is the cost of the 

 mixture? (See Lesson 11.) 



2. Suppose it takes two applications to cure the 

 blight and each application requires a day's time, 

 worth $1.00. What is the cost of the cure? 



3. How many bushels of potatoes, at 50 cents a 

 bushel, will it take to pay the cost of this spray? 



