86 
VEGETABLE GARDENING 
The use of contaminated manure may also introduce dis- 
eases. Sterilization of the soil in hotbeds or cold frames 
may be necessary, and disinfection of certain vegetable 
seeds is desirable. Plowing and cultivating at just the 
right time often prove effective preventive measures ; and 
clean tillage and the destruction of refuse after harvest- 
ing crops may be the means of avoiding serious losses. 
125. Spraying. — Notwithstanding all general preven- 
tive 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: (1) 
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 and dusters. — 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 chamber is an advantage in securing an even and con- 
tinuous discharge. Over 100 pounds pressure is essen- 
tial 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 answer the purpose in small home gardens. 
Knapsack sprayers are very convenient on small areas 
where 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. Plant lice some- 
