April, ’24] 
mccolloch: corn-ear worm 
321 
were 40 inches apart and the hills 36 inches. Shortly after coming up, 
the com was thinned to two plants in a hill. 
Presentation of Data 
The problem of reducing earworm injury to corn by varying the date of 
planting involves a study of many factors. Because of the variation in 
climatic conditions and in the abundance of the insect in different years, 
any recommendations should be based on the average of a number of 
trials. The period covered by this study represents five good corn 
years, two fair years, and three years when the yields were very poor. 
From the standpoint of the abundance of the earworm, there were five 
years of severe injury, three of moderate injury and two when the in¬ 
festation was light. 
Data were taken on all phases of climatic conditions and plant 
growth which are associated with earworm activities. Since space will 
not permit of a full discussion of the data, emphasis is placed on the 
yields and the percent of ears injured, and the data relating to these two 
points are summarized in Table I. The results are also arranged to 
show the frequency with which maximum yields and minimum injury 
were obtained with relation to the date of planting. 
An analysis of the data presented in Table I shows that, from the 
standpoint of maximum yield and minimum earworm injury, corn 
should be planted between April 15 and May 1 at Manhattan, Kansas. 
The plots planted May 1 show an average increase in yield over those of 
April 15 of from 3.4 percent in the case of Kansas Sunflower to 15.5 
percent for Boone County White. At the same time there was a de¬ 
crease in the number of ears injured of from 2.3 to 3.4 percent for all 
varieties except Hildreth. The yields of the May 15 plantings were from 
3 to 5.5 percent lower than those of May 1, while the earworm injury was 
from 12.6 to 15 percent higher. After May 15 the yields decreased 
rapidly with the delay in planting and the injury increased. 
While the average yield for all varieties during the ten-year period 
was highest for the May 1 planting, yet the data show that maximum 
yields were obtained with greater frequency in the April 15 plots. 
In the case of the number of ears injured, however, the frequency data 
favor the May 1 plots. 
In addition to the data presented in Table I, notes were taken on the 
date and period of silking, number of eggs deposited on each variety, 
percent of grain injury and number of overwintering pupae. The 
results of the study of silking and number of eggs deposited were dis- 
