GO 



Total Counts of Ants and Aphids, Galesburg, June and July, 1908 



From the above tabulation of the totals for these dates, it will 

 be seen that while the oats plot contained about as many ants as any 

 of the others, it contained only about a tenth of the number of root- 

 lice found in the other plots at the first three counts; and these were 

 no doubt migrants from the other plots or the descendants of such 

 migrants. That it should have been so invaded by root-lice from ad- 

 jacent plots by the 5th of July, over forty days after planting, that 

 the infestation was now virtually equalized, is consistent with what 

 we have found in similar cases, and it illustrates forcibly the fact that 

 no field of corn is safe against this insect, even tho it may start 

 free from the root-lice in spring, as long as adjacent fields are in- 

 fested l)y it. Nevertheless, the larger yield of the oat-ground plot 

 than that of the cultivation ])lot indicates, as we should anticipate, that 

 rotation to oats makes in the end a more effective clearance of a field 

 than a deep spring preparation of the soil. 



The fact must not be overlooked, however, that rotation to small 

 grains acts slowly in spring, giving the ant-aphis inhabitants of the 

 field sufficient food for some time, and ample opportunity to move, on 

 foot and on the wing, to other fields, while deep and thoro stirring 

 produces its eft'ect at once, before the planting-time of the com, killing 

 and keeping down the food plants of the aphids, and so dispersing 

 and disarranging the insect colonies as greatly to reduce the numbers 

 of the root-lice. 



Summary 



1. The principal measures of protection against the corn root- 

 aphis are rotation of crops ; an early and deep plowing, followed by 

 the repeated deep disking, of corn ground heavily infested by ants or 

 known to have borne a crop injured by the root-aphis; and the use of 

 repellent substances at planting-time, not by direct application to the 

 seed, (which is dangerous tO' germination and early growth,) but by 

 previous mixture with chemical fertilizers or other powdered sub- 

 stances, to be dropped with the seed by means of a fertilizer-dropper 

 attached to the corn-planter. Pages 1-4. 



