396 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 9 



(3) Sixty-three per cent arsenate of lead is equally as effective as 

 pure arsenate of lead and costs less. 



Experimental work with dust sprays was continued in 1915 for the 

 purpose of confirming the results of 1914 and determining the following 

 points: (1) the number of applications necessary to control the corn-ear 

 worm; (2) the value of different carriers for arsenate of lead, such as 

 lime, flour, and sulphur; and (3) a comparison of 75 per cent arsenate 

 of lead with 50 per cent arsenate of lead. 



To determine the first point, eight plots of corn, each one-fifth of an 

 acre in size, were selected. Plot 1 was dusted once, plot 2 twice, and 

 so on to plot 8 which was dusted eight times. The dust used in this 

 experiment consisted of 75 per cent arsenate of lead and 25 per cent 

 sulphur, and was applied to the corn silks by shaking from an ordinary 

 cheesecloth bag. Two check plots were used with this and the fol- 

 lowing experiments. The average of these two check plots is given in 

 the tables. The results of the first experiment are given in Table I. 



Table I i 



From the table it will be seen that there is a marked reduction in 

 the percentage of ears injured with each additional dusting. The 

 per cent of ears injured, however, does not represent the true amount 

 of corn-ear worm injury. The number of grains injured and the dam- 

 age done by the molds and fungi which accompany such injury more 

 nearly represent the actual damage. It will be noticed in the table 

 that these types of injury decrease as the number of dustings are 

 increased. The results of this experiment confirm the results of the 

 previous work in that from 40 to 50 per cent of the normal number of 

 ears injured can be brought through without injury and that the grain 

 and mold injury can be rendered practically negligible. 



1 The data in this and the following tables are based on one-fifth acre plots. 



