10 BULLETIN 592, U. S. DEPARTMENT OF AGRICULTURE. 
Lesson 16.—Plant Diseases. 
1. Physiological troubles. 
2. Fungus parasites. 
3. Bacteria and plant disease. 
Illustrative material—Mounted specimens showing plant diseases. 
Special reference.—Collection and Preservation of Plant Material for Use in the 
Study of Agriculture, Farmers’ Bulletin 586. 
Lesson 17.—The Control of Plant Diseases. 
1. Value of sanitation and general preventive measures. 
2. Disease-resistant varieties. 
3. Spraying and pruning as a means of control. 
Special references.—The following Farmers’ Bulletins: 243, Fungicides and Their 
Use in Preventing Diseases of Fruits; 284, Insect and Fungus Enemies of the Grape 
East of the Rocky Mountains; 440, Spraying Peaches for Control of Brown Rot, Scab, 
and Curculio; 492, The More Important Insect and Fungus Enemies of the Fruit 
and Foliage of the Apple. Articles in the following Yearbooks: 1895, Cause and 
Prevention of Pear Blight; 1896, Diseases of Shade and Ornamental Trees; 1908, 
Development of Farm Crops Resistant to Disease. 
Exercise 4.— Mixing Fungicides. 
The suggestions for mixing insecticides and spraymg tor insect 
pests will apply to Exercises 4 and 5. 
Lesson 18.—Some Common Diseases of Orchard Fruits. 
1. Diseases attacking the pome fruits. 
2. Diséases attacking the stone fruits. 
3. Miscellaneous diseases of importance. = 
Special references——The following Farmers’ Bulletins: 243, Fungicides and Their 
Use in Preventing Diseases of Fruits; 440, Spraying Peaches for the Control of Brown 
Rot, Scab, and Curculio;-492, The Important Insect and Fungus Enemies of the 
Fruit and Foliage ofthe Apple. Peach Scab and Its Control, Department Bulletin 395. 
EXERcISsE 5.—Spraying for Fungus Diseases. 
Lesson 19.—Frost Protection. 
1. Physics of frost formation. 
2. Foretelling frost. 
3. Injury due to freezing temperatures. 
4. Methods of protection and control. 
Special references.—Articles in the following Yearbooks: 1909, Prevention of 
Frost Injury to Fruit Crops; 1914, Story of the Thermometer and Its Uses in 
Agriculture. The following Farmers’ Bulletins: 104, Notes on Frost; 401, Protec- 
tion of Orchards in the Pacific Northwest from Spring Frosts by Means of Fires and 
Smudges. 
Lesson 20.—Principles of Pruning. 
1. A study of fruit buds. 
2. Bearing habits of trees. 
3. Pruning for wood v. pruning for fruit. 
4. Pruning tools. 
Special references.—Articles in the following Yearbooks: 1895, Principles of Prun- 
ing and Care of Wounds in Woody Plants; 1898, Pruning of Trees and Other Plants. 
Pruning, Farmers’ Bulletin 181. 
