June, '22 European corn borer discussion 239 



There was one instance where it was effective. It may have been 

 due to slightly later planting. It was an isolated field hedged in on 

 two sides by woods, and this field infested last year was this year almost 

 free, due I think to the lateness of planting; although the man did 

 carry out an extensive cleanup campaign last fall. 



Mr. W. R. Walton : I would like to ask Mr. Spencer if I may whether 

 he finds that the physical condition of the soil affects migration of the 

 larvae? Does he not find that migration is less in heavy soil than in 

 light soil ? 



Mr. G. J. Spencer: I will refer that to Mr. Crawford. 



Mr. H. G. Crawford: In connection with this point I might say 

 that we carried out a series of experiments, burying ten stalks in loose 

 bundles and single layers, at depths of six inches, throughout the 

 season. The chief governing factor in the early season in the rate of 

 larval emergence from various buried stalks was the moisture of the 

 soil. They cam.e up through very heavy clay soil to all practical pur- 

 poses at the same rate of speed as they came up through sand. In 

 fact, sand soil is the most retentive of larvae of any soil used in the 

 experiments. Some of these experiments were put in between the fourth 

 and the eleventh of September, so there was no temperature factor 

 slowing them up in the sand at least during the first part of the season. 



Mr. W. R. Walton: It seems curious that yours seem to be directly 

 opposite to the results which we secured in similar experiments. 



Mr. H. G. Crawford: In regard to the m^atter of control for the 

 individual farmer — for effective results it has to be done on a community 

 basis. However, there is the point to bear in mind that the early plant- 

 ed com is very severely infested and ruined, in a case of sweet com — 

 one hundred per cent. loss. In the same vicinity the late planted com, 

 though fairly heavily infested, is not severely damaged, and the individ- 

 ual farmer could thus stop severe loss comparatively easily. In our 

 efforts next year to get a group of the farmers to follow as many of our 

 suggestions as possible, we are going to lay particular emphasis on 

 putting com in as late as is safe in the community. If they put it in 

 as late as they feel, as practical growers, is safe, it will cut down the 

 loss; though we will still be carrying infestations up to sixty, seventy 

 and in some cases eighty per cent. 



Mr. E. p. Felt: Has Mr. Crawford any definite information, or an 

 approximate idea of the relative area in the badly infested section, 

 which was severely damaged by com borer? I asked that question 

 last fall. Has he an answer now? 



Mr. H. G. Crawford : I have not. It would involve the study of 

 every com field involved, as one field will be less than twenty-five 



