14 Farmers’ Bulletin 1206. 
CONTROL MEASURES. 
In many cases during recent invasions of the corn earworm, the 
infestation started in hairy vetch and spread thence to young corn, 
cotton, and alfalfa. (Growers who have suffered from invasions of 
this pest have hesitated about continuing to plant vetch. However, 
it is not necessary to reduce the acreage of vetch as this pest can be 
controlled by a little effort. As has previously been mentioned, vetch 
intended for a hay crop generally escapes serious injury because it 
usually is cut before the caterpillars are of sufficient size to do much 
damage. That part of the crop, however, which isintended for seed and 
which is left uncut for several weeks longer, that the seed may ripen, 
is subject to more serious injury; for during this period the caterpil- 
lars do their most destructive work. The seed crop of vetch, there- 
fore, should be carefully examined from time to time; and if the 
caterpillars are found to be abundant, an insecticide should be applied 
at once, or if it is not possible to do this, the crop should be cut for 
hay. The quality of hay will not be as good as that from earlier-cut 
vetch, but the hay will be worth more than the small quantity of seed 
that the crop will yield. 
During favorable seasons vetch and oats, planted together in rich 
soil, generally make a very dense growth. Therefore it is not advis- 
able to use a large sprayer to apply an insecticide, for not only is it 
difficult to apply a spray so that it will reach the lower parts of the 
plants but the trampling of the dense growth of the crop results in 
much damage to the plants by their being broken off, bent over, or 
mashed down. The area to be treated is generally small and may be 
easily treated with portable machines, either sprayers or dusters. 
Every farmer should possess such an outfit. They are not neces- 
sarily expensive and may be purchased in almost any town. Often 
such an implement will more than pay for itself with a single usage. 
Every farmer should keep in touch with a concern that’ supplies 
standard insecticides, such as arsenate of lead, Paris green, or calcium 
arsenate. He should also keep in touch with an entomologist who 
can supply the necessary advice immediately. Nearly every State 
in the Union has such an official. It would be advisable also to 
have on hand a copy of Farmers’ Bulletin 908 on “ Information for 
fruit growers about insecticides, spraying apparatus, and important 
insect pests.” 
SPRAYING FOR THE CATERPILLARS. 
When the caterpillars are feeding on the foliage of plants, such as 
vetch or alfalfa, they may be killed by applying a poison spray (fig. 
11). This spray should be applied with as much force as possible 
so as to reach the foliage at all depths. A mixture of 1 pound of 
