Whorled Milkweed 
27 
feet deep. There is good drainage. The milkweed occurs in a 
field which was formerly cultivated in ordinary farm crops, but 
has been abandoned for a number of years. As previously men- 
tioned this area is on the main sheep driveway thru the Monte- 
zuma Valley and has been used as a camping ground by bands 
going thru. This field, which contains about eleven acres in- 
fested with milkweed, was responsible for the loss of 1,600 head 
of sheep in the years from 1916 to 1918, inclusive. 
The County of Montezuma co-operated with the State in the 
experimental work done on this area during 1918. The 1919 work 
was carried on by the State Experiment Station in co-operation 
with the state entomologist. 
Plot I. Spraying with Salt Solution. — For this plot a small 
patch of the milkweed about 10 feet in diameter was used. The 
application of the spray was made with a hand spray pump. Five 
gallons of salt solution were used for each application. The 
strength of the solution was 2 pounds of salt to a gallon of wa- 
ter. The first application was made on June 15, 1918, when the 
plants were about 3 inches high. The tops were killed back to 
the ground. On July 8, growth had again been made to a height 
of about 3 inches, from the roots, and the second application was 
given. The tops were again killed back. On July 23 the third ap- 
plication was made, when the growth had again reached a height 
of about 3 inches. On August 23 it was estimated that the 
growth made between July 23 and August 23 was about 4 per 
cent, as thick as the original stand, but the shoots seemed 
healthy, were growing well, and were about 4 inches high. No 
further applications of salt were made and the milkweed on the 
plot seemed uninjured except that it had been thinned out. 
In the early summer of 1919 no shoots of milkweed made 
their appearance on this plot and an examination of the soil 
showed that a crust had been formed by the salt in the 
upper 2 inches of the soil. This crust was dark brown and hard. 
In this dark stratum of soil the milkweed stems were all black- 
ened and dead, but in the soil below, the roots and rootstocks 
were alive. At no time during the summer did a single shoot of 
the milkweed succeed in making its way thru the salt crust. One 
hundred per cent, eradication was obtained on this plot. Figure 
21 shows the condition of this plot at the beginning of spraying 
in 1918 and again in July, 1919. Russian thistle succeeded in be- 
coming established on top of the crust. It must be noted that 
the season of 1918 was a very dry one, not a single good rain 
falling from June 1 to September 1. Under these conditions, the 
