PROGRESS REPORT ON THE EUROPEAN CORN BORER 
43 
The experimental fields were located where the corn borer has 
become well established, and the infestation and injury to the corn 
in these fields represented ordinary conditions. Moreover, the fact 
that these, varieties were grown in adjacent plats under the same 
cultural conditions provides an indicative basis for comparison of 
relative susceptibility of varieties and types. The fields wherein 
these plats were located received a thorough clean-up and plowing 
during the preceding fall, or in the spring, so that the conditions 
of infestation prior to planting were much better than those exist- 
ing in commercial fields of the vicinity. Most of the subsequent 
infestation in these plats, particularly that by the first generation, 
Fig. 22. — European corn-borer injury to grain of dent field corn. The cobs and ear 
stems were also badly tunneled bv the borers. The experimental plat from which 
these ears originated showed 28.7 per cent grain injury, with 100 per cent of ears 
and stalks infested. Medford, Mass., October, 1922 
is believed to have been caused by the flight of moths from adjoin- 
ing fields. The results of the examinations of the experimental plats 
are shown in Table 5. 
The counts shown in Table 5 were made at the time of harvest; 
50 ears were selected at random from each plat of field corn when 
mature and 100 ears selected in the same manner from each plat of 
sweet corn at the roasting-ear stage. The stalk infestation was based 
upon an examination of 100 stalks from each plat. The actual grain 
injury to sweet corn is not indicative of the real loss, as many ears 
which suffered only slight damage to the grain at the roasting-ear 
stage were rendered unfit for market purposes or for canning. The 
grain injury to dent corn in comparison with flint corn is somewhat 
affected by "the fact that in the 1920 series 4 of the varieties of dent 
corn did not mature under Boston conditions. According to experi- 
