10 
and thus large numbers of the insects could be killed early in the sea- 
son before they had opportunity to spread to peas. 
In Delaware it has been shown that the practice of keeping the land 
well fertilized and frequently cultivated enables the peas, in spite of 
aphis attack, to produce better crops than would otherwise be made. 
Alternate host plants.—The subject of alternate host plants is an 
important one, since the pea, being an annual, is not available as food 
for this aphis during winter. It is desirable to ascertain all of the host 
plants of the pea aphis, and more especially the weeds, as some one or 
Fig. 7.—Section of a 600-acre pea field, rows one mile long, showing spraying outfit ready for 
work. Peas finally saved by brush-and-cultivator method. 
more of these may be factors of importance in the life economy of the 
species. It might be necessary in the future, should the depredations 
of this insect increase, to limit the growing of clover and other legumes, 
as well as other alternate host plants, if such be found, in the vicinity 
of pea fields. If all of the principal alternate plants could be discov- 
ered this might furnish a solution of the problem of how to deal with 
the insect. 
Approved: 
JAMES WILSON, 
Secretary of Agriculture. 
WASHINGTON, D. C., January 21, 1909. A6-—49 
O 
