18 BULLETIN 721, U. S. DEPARTMENT OF AGRICULTURE. 
times make serious inroads upon the stand of beets. These pests may 
be destroyed by the use of poison or by trapping. 
WATER. 
Excess or deficiency of water may be a limiting factor in sugar- 
beet production. 
Precipitation. — In the humid sections of the Bugar-beet area beet 
growers depend upon rainfall and snow for the necessary supply of 
soil moisture. Usually the snow and the spring rains put the soil in 
good condition for planting, and the summer rains keep the crops 
growing until the end of the season. Whether the precipitation will 
furnish an excessive amount of moisture for the soil will depend upon 
soil conditions as well as upon the amount of precipitation. For 
uniform soil conditions, however, the consideration of precipitation 
is of vital importance in the growing of sugar beets. Excessive pre- 
cipitation may be detrimental in two ways: (1) By preventing a 
proper preparation of the seed bed, and (2) by saturating the soil to 
such an extent that the air is excluded from the plant roots and the 
proper growth of the plants thereby prevented. Likewise, a deficiency 
of precipitation may make a proper preparation of the seed bed impos- 
sible, or it may put the seed bed in such condition that the germina- 
tion of the seed or the subsequent growth of the plants may be 
impaired. Excessive precipitation may be remedied under cer- 
tain conditions by a proper system of drainage. (See pp. 21-23.) 
The lack of moisture may be remedied in part (1) by putting the 
proposed seed bed in a proper condition to catch and hold the 
fall and winter moisture; (2) by subsequent cultivation, where- 
by a mulch is formed on the surface of the field, thereby retarding 
evaporation; and (3) by supplying the soil with a suitable amount 
of humus. 
Irrigation. — The use of irrigating water is theoretically simple, but 
its practical application is very complex, calling for a knowledge of 
plant growth and soil requirements based upon experience and good 
judgment. It is one of the most important factors in sugar-beet 
production in the semiarid regions. Good crops are sometimes ruined 
by a lack of knowledge of the water requirements of plants and 
by want of experience in applying the water. 
There are four sources from which irrigating water may be ob- 
tained, namely, from reservoirs, direct from streams, from flowing 
wells, and by pumping. A reservoir is a storage place in which an 
excess of water due to melting snows or from other sources may be 
stored for future use. Stream irrigation implies either a continuous 
or an intermittent flow of water in a river bed which may be drawn 
upon when needed. Pump irrigation is practicable when the sub- 
