128 PRINCIPLES OF FARM PRACTICE 



The best possible preparation of the seed bed should be 

 made for all crops, but deep plowing is especially important 

 in potato growing. The plowing should be followed by 

 thorough cultivation, deep at first, but shallow in all the 

 later cultivations, because the potato roots grow near the 

 surface of the soil. Ridging, or hilling, is not necessary, 

 except just enough to protect the tubers from sunburn. 



The control of injurious insects, such as the Colorado 

 potato beetle, and of diseases, such as late blight, requires 

 considerable attention. With all the conditions of climate, 

 soil, variety, and cultivation favorable, it is possible to have 

 a crop failure because of a failure to control either insects or 

 diseases. Fortunately, control of these two factors is possible 

 although it requires labor and some expense. 



The general procedure is as follows : to destroy the spores 

 of such diseases as potato scab, brown rot, black leg, stem 

 rot, etc., the seed tubers should be treated, before planting, 

 with a solution of formaldehyde (made by adding one pint 

 of formaldehyde to thirty gallons of water) or with a solution 

 of corrosive sublimate (four ounces of corrosive sublimate to 

 thirty gallons of water) . 



During the growing season in order to control blight and 

 other diseases, the plants should be sprayed from time to 

 time with a Bordeaux mixture (5-5-50 strength); to con- 

 trol insects a mixture containing arsenic, such as Paris green 

 or arsenate of lead, should be used. 



Details for the preparation of these mixtures, and the 

 methods and time for their application will be found in the 

 appendix. 



If possible only those tubers free from diseases should be 

 used as seed. The seed should be planted in clean land. 

 A long rotation should be practiced, because if soil is once 



