154 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



corn planted later and that this difference was probably due to the 

 fact that the early planted corn finished its silking before the third 

 brood came on in full force. 



In support of finding No. 1, it may be said that in the spring of 

 1909 four 10' X 10' plots, examined in a field which on September 22 

 of the preceding fall showed sixty-four per cent of the ears infested 

 and which had been plowed in early winter, gave no living pupae; 

 while two 16' x 16' plots in a field which showed a somewhat larger 

 per cent of infestation the preceding fall and which was undisturbed 

 until spring showed six living pupge. 



In regard to finding No. 2 it may be said that while, as stated 

 earlier in this paper, our examinations indicate that most, if not all, 

 the pupa? of corn ear-worm winter in the soil of infested cornfields, 

 there is no doubt that the presence of weeds in and around the corn 

 enables many belated larva? to finish their growth. Weeds, therefore, 

 should not be tolerated in such locations. The parasitism of the 

 larvge infesting weed patches and alfalfa fields, particularly the 

 latter, in the autumns of 1908 and 1909 has been exceedingly high 

 and the early hard frosts have destroyed large numbers. Possibly 

 these agencies may account for the absence of pupae in such places. 



In order to determine the exact relation existing between time of 

 planting and injury and to find out the exact cause of this difference, 

 six standard varieties of corn were planted at different periods. A 

 two and one-half acre plot of ground of uniform character was 

 selected and divided into six plots. In each plot three 150-feet-long 

 rows of each of the six standard varieties of corn were planted. These 

 strains ranged from one hundred and fifteen to one hundred and 

 thirty-five days in time of maturing. They were Leaming, Reid's 

 Yellow Dent, Boone County White, McAuley, Kansas Sun Flower, and 

 Hildreth. The land had previously been in use for wheat breeding. 

 The soil was prepared by spring plowing and working. The corn 

 was cultivated at first deeply, then shallowly, and kept thoroughly 

 clean to the end of the season. The plots were planted as follows : 

 Plot No. 1 April 15th; plot No. 2 May 1st; plot No. 3 May 15th; 

 plot No. 4 June 1st ; plot No. 5 June 15th ; plot No. 6 July 1st. Except 

 for cold weather in the spring, some wind and hail in July, the season 

 was excellent for corn production until the middle of August when 

 the drought became so severe that the yield of plot No. 6 was practi- 

 cally ruined. Plot No. 1 produced corn on cob at the rate of 39.8 

 bushels per acre; plot No. 2 46.5 bushels; plot No. 3 49.7 bushels; 

 plot No. 4 46.7 bushels; plot No. 5 26.1 bushels; and plot No. 6 corn 

 hardly worth gathering. Plots No. 3 and No. 4 produced more corn 



