12 FARMERS’ BULLETIN 141. 
a deposit of fine mud. This is practicable only where the irriga- 
tion system is without a settling reservoir, which is ‘in itself an 
undesirable condition, but in the few cases where it can be applied 
the process is simple and inexpensive and the results good. 
SPRING CULTIVATION. 
Alfalfa fields in a weevil-infested region should be cultivated thor- 
oughly in the spring with the spring-tooth harrow, disk harrow, or 
a similar tool, provided the crop is valuable enough to warrant the 
expense of the operation. Under conditions where cultivation is 
especially desirable, as where water is scarce or the soil does not 
naturally retain moisture well, this may increase the amount of the 
first crop as much as 50 percent. It will cost from 60 cents to $1.25 
per acre. In nearly every case it will be necessary to go over the 
field at least twice; and if the soil is in such condition that a double 
harrowing does not pulverize the soil and kill the weeds and grass, 
systematic manuring, cropping, and cultivation to improve the soil 
are desirable. Spring cultivation has no appreciable effect on the 
weevils, but merely hastens the growth of the alfalfa so as to give a 
larger yield when the attack of the larve in May or June makes early 
cutting necessary. 
SPRING SPRAYING. 
As soon as the weevils begin feeding upon the leaves of the plants, 
which usually happens early in April, the field may be sprayed with 
from 50 to 100 gallons per acre of a mixture of arsenite of zine and 
water, in the proportion of 4 pounds of powder in 100 gallons. Owing 
to war conditions it may be impossible to obtain this poison at the 
present time. Arsenate of lead has not so far proved successful as an 
early spring spray. 
On several occasions when it was intended to spray fields in early 
spring, circumstances prevented it, and the spray was appled about 
May 1, after many larve had hatched from the eggs and attacked 
the crop. In several of these cases the results were good, although 
the amount of foliage which must be covered is larger at this time 
than in early spring. Arsenate of lead, in the usual orchard strength 
of 4 pounds to 100 gallons of water, was as effective at this time as 
arsenite of zinc. 
The attachment which is recommended for use with the hand-pump 
or gasoline-engine outfit for spraying alfalfa fields resembles the 
potato or beet sprayer. It is a horizontal pipe, 3 feet above the 
ground, fastened across the back of the truck of the power sprayer 
(fig. 7) or the wagon in which the hand pump is carried, and stiffened 
by lashing to a 2 by 4 scantling as long as the pipe itself. To pro- 
vide for the attachment of the supply hose from the pump and the 
nozzles which distribute the liquid, the pipe is built up of 30-inch 
pieces of one-half inch galvanized iron pipe, coupled by T’s, except 
a 
