February, ’24] 
caffrey: corn borer research 
113 
that certain varieties of field corn and of sweet com are less suceptible 
than others to severe injury by the corn borer. 
This apparent difference in susceptibility has usually been involved 
with the time of planting and also with the seasonal habit or size of 
growth and the period of maturity. None of the varieties tested to date 
have shown any indication of possessing entire immunity from attack, 
even in the presence of a light or medium infestation, although some 
varieties suffered much less injury than others, particularly the large 
dent varieties producing large heavy stalks and large ears. 
Judging from the results already secured, it is believed that continued 
investigations will evolve a system of varietal selection and a planting 
schedule that will be very effective as a cultural practice. In addition 
to the Federal work, cooperative projects with the agronomists to de¬ 
termine these points, are now being carried on with the State of Ohio, 
and a similar project is under contemplation with the State of Massa¬ 
chusetts. 
The possibility of ascertaining morphological or physiological charac¬ 
teristics that are conducive to resistance in different varieties of corn, is a 
problem that it is hoped to approach in the near future. 
Plowing 
The effectiveness of plowing down infested cornstubble, weeds and 
crop refuse, as a farm practice in reducing corn borer damage, has been 
made the subject of extensive investigation in New England' New York 
and recently in Ohio. 
While much remains to be learned concerning the behavior of borers 
thus treated, under all conditions, it has been determined in general, 
that in New England and New York, the thorough plowing under of 
infested material, particularly during the late Autumn, leads to the 
destmction of a large proportion of the larvae contained therein. Lar¬ 
vae which were plowed under in the early Autumn or in the Spring have 
migrated to the surface in large numbers and the question concerning the 
ultimate fate of such larvae in cleanly plowed fields, is still under 
investigation. 
Under all conditions, however, it has been observed that the effective¬ 
ness of this measure is dependent to a large degree upon the thoroughness 
with which the plowing is done. Breaking down the cornstalks, corn¬ 
stubble or other standing material before plowing, and disk harrowing 
immediately after plowing in heavy soils, has been found to greatly 
increase the effectiveness of the work. 
