THE EUROPEAN CORN BORER, PYRAUSTA NUBILAUS 
HBN., VERSUS THE CORN EARWORM, HEUOTHIS 
OBSOEETA FAB . 1 
By Geo. W. Barber 
Scientific Assistant, Cereal and Forage Insect Investigations, Bureau of Entomology, 
United States Department of Agriculture 
The spread of the European com borer, Pyrausta nubilalis Hbn., in the 
northeastern portion of the United States, during the last few years, creates 
interest in what will happen when this insect reaches the sections of the 
country where the com earworm, Heliothis obsolete, Fab., seriously 
damages the com crop. In the area infested by the European com borer 
at present the com earworm is present annually, but usually in small 
numbers, and seldom does serious injury to the com. 
In the late summer and fall of 1921 the com earworm was abundant 
in late sweetcom and in field com in eastern Massachusetts. This was 
probably due to the occurrence of a second brood of the insect, which 
apparently was made possible either by the rather mild preceding winter 
or by the abnormally long growing season of that year. The infestation 
in some fields ran as high as 90 per cent of the ears, and injury was very 
apparent over a considerable area. 
In the same season the European com borer was also destructive in 
certain fields infested by the com earworm, forecasting the condition 
which one might expect to find in the southern portion of the Com Belt 
should the European com borer ever reach that section. 
Larvae of both species were commonly found feeding in and on the 
same ears of com, frequently their burrows uniting and adjoining, while 
the larvae were in close proximity, each apparently too much occupied 
with the feast to be mindful of its neighbor. 
Although not present in such large numbers, the larvae of the corn 
earworm were able by the time they completed feeding to inflict more 
actual grain loss than the larvae of the European com borer, because of their 
greater feeding capacity and because their work was, for the most part, 
concentrated on the kernels, whereas the European com borer larvae 
feed throughout all parts of the ear and stalk, thus having a much wider 
range of activity. The feeding of the European corn borer larvae, how¬ 
ever, results frequently in more injury than is apparent in actual destruc¬ 
tion of the grain, by injuring the stalk and particularly the peduncle of 
the ear. This often results in a reduction of the number of kernels 
forming on the ear. In 1921 many of the ears showed undeveloped 
kernels, particularly at the tips, which was undoubtedly due, at least in 
part, to the injury to other parts of the plants by the European com borer. 
A field of about an acre of Longfellow flint com was used to obtain the 
information contained in this paper. The ears studied were selected at 
random and showed the average condition of the ears of the whole field. 
Ears shown in Plate 1 are average ears selected to show different types 
of injury rather than a maximum amount of damage. 
When the counts shown in Table I were made (October 14, 1921) the 
com earworm larvae, in nearly all cases, were feeding in the ears. By 
October 20, 1921, when Table II was prepared, many of the larvae of 
1 Accepted for publication Nov. 19, 1923. 
Journal of Agricultural Research. Vol. XXVII, No. 1 
Washington, D. C. Jan. 5, 1924 
Key No. K-124 
73430—24-5 
(65) 
