THE ALFALFA CATERPILLAR. ry. 
SYSTEM OF CROP CULTURE. 
For the reasons just given the control problem, in dealing with 
this alfalfa pest, resolves itself to one of the method of handling the 
crop. Not long after the Bureau of Entomology began observations 
in the Imperial Valley the writer was informed by well-to-do ranchers 
that not all alfalfa fields or even all ranches were affected by the 
caterpillars, there being apparently certain conditions regulating the 
devastation. One cause for this, as noted earlier in this paper, was 
the presence of stock in certain fields, but even in hay ranches there 
was a variation in the numbers of the caterpillars. Accordingly 
there was outlined a series of experiments in which, in certain fields 
under observation, definite methods of management were tested to 
see whether some of them would not reduce or perhaps entirely elimi- 
nate the damage. Before describing the conditions existing in these 
fields it would be well to consider, first, the conditions existing in 
certain other alfalfa fields not under the direction of the agents of 
the bureau which suffered greatly because of the pest, the owners 
often losing an entire crop. The first fact noted was that the cater- 
pular damage in such fields seemed to be correlated with the condi- 
tion of the soil. A field seriously damaged often revealed a poor 
soil; at least, a soil not well adapted to alfalfa culture, and conse- 
quently producing a slow-growing crop. Of course, not all the fields 
damaged were of such poor soil, for some of the very best alfalfa 
fields were seriously ravaged, but in these latter cases this was at- 
tributable to other factors, such as time and careless manner of cut- 
ting and time of irrigation. The sandy loams or light soils are the 
best for alfalfa production, and consequently least damaged. A 
heavy soil can be greatly improved and the growth of the alfalfa 
increased by deep plowing and thoroughly preparing the seed bed 
at time of seeding the crop and then renovating the alfalfa yearly by 
disking or by the use of an alfalfa renovator. 
The worst conditions noted were those in which the attack of the 
caterpillar was due to delayed cutting of the hay crop and due quite 
often to the fact that many of the ranchers were trying to cultivate 
more land than it is possible for one man to farm successfully. With 
such ranchers some of the following defects are observable in their 
treatment of the hay crop: First, there is often insufficient water 
used to provide for the prompt development of the alfalfa crop. An 
abundance of water is very necessary, as it enables the alfalfa to make 
faster growth, and thus the farmer can reap his crop sooner and be- 
fore the caterpillars have effected much damage. Second, the crop 
is not cut early enough in the majority of cases—about 90 per cent— 
that is, the alfalfa is too far advanced in bloom when cut, and this 
delayed cutting enables the caterpillars to mature successfully. The 
[Cir. 133] 
