86 VEGETABLE GARDENING 



The use of contaminated manure may also introduce dis- 

 eases. Plowing and cultivating at just the right time 

 often prove effective preventive measures; and clean 

 tillage and the destructioa of refuse after harvesting 

 crops may be the means of avoiding serious losses. 



125. Spraying. — Notwithstanding all general preventive 

 measures, spraying is often necessary to avoid heavy 

 damages. The fundamental principle involved is that 

 of protection. If the operator uses an insecticide it serves 

 as a poison or a repellent and should be applied before the 

 enemy has made a serious attack ; and if injury is expected 

 from fungous diseases, by the application of a fungicide 

 the parts in danger of infection are armored with material 

 which will prevent the entrance of the parasites. 



Five things are important in successful spraying: (i) 

 Know your enemy; (2) select the most effective poison 

 for its control; (3) spray thoroughly; (4) spray as often 

 as may be necessary under existing conditions; (5) spray 

 at the proper time. 



126. Spray pumps. — Inexpensive pumps are seldom 

 satisfactory. The best materials should be used in the 

 construction of spray pumps ; all metal parts which come 

 in contact with the solutions should be made of brass 

 or copper to prevent serious corrosion. A large air cham- 

 ber is an advantage in securing an even and continuous 

 discharge. Over 100 pounds pressure is essential to the 

 best work in orchard spraying, but less than this is 

 effective in garden operations. 



Various types of pumps are available. The bucket 

 pumps, which may be bought for a few dollars, answer 

 the purpose in small home gardens. Knapsack sprayers 

 are very convenient on small areas wh^re the crops are 

 planted close together, and in large plantations when 

 growth is so far advanced as to prevent the use of barrel 

 or power sprayers. It is not an easy task to carry and 

 operate a knapsack sprayer, but it is unquestionably the 



