BREEDING SWEET CORN RESISTANT TO THE CORN 
EARWORM 
By G. N. Coiains, Botanist , and J. H. Kempton, Scientific Assistant , 
Office of ^Acclimatization and Adaptation of Crop Plants and Cotton Breeding , 
Bureau of Plant Industry , United States Department of Agriculture 
INTRODUCTION 
The production of sweet com (Zea mays) in the southern part of the 
United States and throughout the American Tropics is seriously inter¬ 
fered with by the ravages of the com earworm (Chloridea obsoleta Fab.). 
The geographic range of this insect is practically coextensive with 
maize culture, extending to the northern boundaries of the United States. 
But Quaintance and Brues 1 state that nowhere in the transition zone, 
comprising in the main the New England States, New York, Pennsyl¬ 
vania, Michigan, Wisconsin, and Minnesota, is the pest of regular occur¬ 
rence or a cause of any considerable damage. For some distance south 
of this region the injury is also comparatively slight, but in many sec¬ 
tions near the southern border of the country sweet com is not grown 
at all, its place on the table being taken by field varieties. 
The exclusion of sweet varieties from these regions may not be entirely 
due to the com earworm, but it is probable safe to consider this insect 
the major factor. 
The com earworm does not confine its depredations to sweet corn, 
but also attacks field varieties. From the fact that northern varieties 
of field corn, when grown in the South suffer much more than do the 
local sorts, it would appear that the especial susceptibility of sweet 
varieties is not due to the character of the seeds alone, and that the 
southern varieties of field com must possess some additional peculiarity 
that renders them at least partially immune. 
A comparison of the general characteristics of northern and southern 
varieties at once suggests that the greater immunity of southern varieties 
may be due to the greater development of husks in the southern varieties. 
Attention was early called to this possibility by Mr. O. F. Cook, 2 from 
observations made on a variety of com growing near Brownsville, Tex. 
This variety produces small ears inclosed in very long husks. Mr. Cook 
noticed that, while many larvae were found inside of the projecting 
husks, few had reached the ears. 
1 Quaintance, A. L., and Brues, C. T. the cotton bou/worm, U. S. Dept. Agr. Bur. Ent. Bui. 50, 
155 p., 27 fig., 25 pi., 1905. 
2 Bionomist in Charge, Office of Acclimatization and Adaptation of Crop Plants and Cotton Breeding, 
Bureau of Plant Industry. 
(549) 
Journal of Agricultural Research, 
Washington, D. C. 
lc 
Vol. XI, No. 11 
Dec. 10,1917 
Key No. G—129 
