by root- worm injury in a way to cause a falling or conspicuous lean- 

 ing of the stalks consequent upon the weakening of the hold of the 

 plant upon the earth thru the destruction of its roots. As there was 

 considerable infestation of some of these fields by white-grubs, in- 

 juries by which have a similar effect, especial care was taken to dis- 

 tinguish injuries by these insects, very readily recognized upon an 

 examination of the roots themselves. 



Of the seventy-one fields examined, twenty-seven were in corn 

 for the first time since they had been planted to some other crop, most 

 commonly oats; fifteen fields were known to have been in corn but two 

 years in succession, and seven others were known to have been in corn 

 for two years, the preceding crops not being ascertained. Eleven 

 fields had been in corn for three years in succession, five for four years, 

 one for five years, three for six years, and two for ten years. The 

 numbers of the five-, six-, and ten-year fields are obviously too small 

 for reliable averages. None of the twenty-seven fields in corn for 

 one year only, showed any trace of root-worm injury; the fifteen fields 

 which were known to have been in corn for only two years in suc- 

 cession exhibited injuries ranging from none to 50 percent, with an 

 average of 19 percent ; and the seven fields which had been in corn for 

 two years, the preceding record being unknown, had been injured in 

 ratios varying from 15 to 70 percent, with an average of 35 percent. 

 Evidently some of these last fields had been in corn longer than two 

 years. The thirteen fields which were known to have been in corn for 

 three years in succession were injured in ratios varying from 20 to 80 

 percent, with an average of 46 percent; and the ratios for the five 

 fields which had been in corn for four years in succession, varied 

 from 25 to 90, with an average of 64. Our available information is 

 thus to the effect that ground in corn for the first year by rotation 

 from some other crop, will not be injured at all by the corn root- worm, 

 any failing which it may exhibit being due to some other injury; and 

 that corn growing on the same ground for the second year is likely to 

 become infested at an average rate of 19 percent, and for the third 

 year at two and a half times that rate. Of course these ratios will 

 vary with the abundance of the insects, which will itself be influenced 

 largely by the prevailing agricultural practice as to rotation. It is 

 obvious, however, that two years is the maximum period during which 

 it is safe to continue land in corn where the root- worm is a prevalent 

 and destructive pest. 



As the corn root-worm beetles emerging in corn fields in mid- 

 summer are presently to be found in numbers outside such fields. 



