252 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
The results of six years’ investigation show that there is a direct 
relation between the number of eggs deposited on a variety and the 
date of planting, and that there are several factors to be considered in 
developing an optimum time to plant corn. Headlee 1 pointed out 
that corn planted about May 1 was less injured by the corn earworm 
than corn planted April 15 or May 15 and later. He attributed this 
to the fact that early planted corn passes through its most attractive 
stage—silking—before the third brood of moths appear, and also that 
corn planted too early suffers a setback from climatic conditions. The 
results of the present studies in general confirm the findings of Headlee, 
and the data on oviposition offer an explanation for this condition. 
In the light of the present investigations, however, the variety of corn 
must be considered with relation to the date of planting, since each 
variety exhibits certain variations with regard to growth, time of silk¬ 
ing, period of silking, and maturing. In addition, there are certain 
morphological characters that may have an influence. As has been 
pointed out, the number of eggs increases with the delaying in silking 
and maturing of the varieties, and the early silking and maturing 
varieties have had the fewest eggs. 
The relation between the total number of eggs found daily during 
the six years, and the average period of silking is shown graphically in 
Figure 7. As seen by this figure, the maximum emergence of the sec¬ 
ond brood of moths is about July 10, and the third brood begins to 
emerge about August 8. Obviously the optimum date to plant corn 
with regard to the earworm would be at such a time as to bring it 
into silk between these two broods. A study of the figure shows that 
corn planted from April 15 to May 15 silks at approximately the same 
time, being but a few days later for each delay of two weeks in sowing. 
In the case of the first two dates of planting, the maximum silking 
period is passed before the emergence of the third brood. The May 15 
plot is just reaching its maximum period of silking when the third 
brood begins to emerge, while the last two plots are in full silk at the 
time this brood is abroad. The variation in the number of eggs on 
the varieties in the earlier plots is due largely to the time of silking 
* with relation to the second brood of moths. 
From the data shown in Table VIII, it is seen that in the greatest 
number of instances the lowest number of eggs were found on the May 
1 plot, with the May 15 plot second, and the April 15 plot third. In 
other words, the corn planted April 15 was in silk during the latter part 
of the period that the second brood of moths were ovipositing. The 
May 1 plot was in maximum silk about August 1, or at a time when the 
second brood had practically disappeared, and the third brood had not 
1 Headlee, T. J., op. cit. 
