PROGRESS -REPORT OX THE EUROPEAN CORN BORER 153 
Regardless of any necessary change in farm practice, the disking 
for small grain on infested corn lands will have to be discontinued 
if the corn borer is to be held in check. Where unavoidable, this 
practice should be limited to fields in which the operations of cutting 
or breaking off the stalks at the soil surface and completely disposing 
of them together with all trash, by burning or otherwise, have been 
carefully conducted. 
In a field where standing stalks were poled down, raked in wind- 
rows, and burned, and the remaining debris plowed under, practically 
all of the borers were killed. Although there were about 5,100 borers 
per acre in the standing stalks before operations began, no living- 
borers could be found in such small portions of trash as remained. 
This method, if widely adopted, would act as a very severe check on 
corn-borer infestation, and therefore it is strongly recommended. 
Although the plowing under of infested cornstalks and corn stubble 
has given encouraging results where carried on in a careful manner 
it should be emphasized that careless plowing leaves many pieces of 
stalks, stubble, weeds, etc., upon the soil surface and is not effective. 
This debris shelters many borers which crawl to the surface after 
being plowed under. They bore into, or encase themselves, in such 
debris, and here many of them transform into moths. Where such 
shelter is lacking the vast majority of the borers finally perish, either 
being eaten by birds, beetles, or ants, or killed by various native para- 
sites or by exposure to the weather. The use of plows with wide bot- 
toms and a chain or wire to aid in burying all debris is an important 
help in doing a clean job. 
The importance of clean plowing was strikingly shown by a series 
of experimental tests at Bono, Ohio. 
Infested cornstalks were plowed under at intervals from late Sep- 
tember to mid-December, 1925, and were surrounded by "recovery 
traps." At least 38 per cent of the borers in these plowed-under 
stalks crawled to the soil surface during the fall and the following 
spring. The remaining 62 per cent died in the soil or were destroyed 
by their natural enemies and weather conditions after reaching the 
surface. 
In tests where the soil surface was practically free of all plant 
debris an average of only 2 per cent of the plowecl-down borers were 
able to find adequate shelter. In similar tests where the quantity of 
stalks on the soil surface was the same as on average fields in the 
vicinity, 13 per cent of the total borers plowed down found adequate 
shelter in debris on the surface. In two other tests where " recovery 
traps," which provided shelter, were placed 25 feet distant from the 
plowed area, and stalks were left on the soil surface in average 
quantity, 22 per cent of the total number of plowed-under borers suc- 
ceeded in entering the surface debris. An additional 5 per cent 
crawled at least 25 feet to the " recovery traps." 
Thus it is shown that under circumstances closely imitating field 
conditions following clean plowing only 2 per cent of the borers 
escaped destruction. On the other hand, where average quantities of 
corn remnants were left on the soil surface, from 13 to 22 per cent of 
the borers survived. 
In certain small tests where minute examination was possible, evi- 
dence was obtained that 28 per cent of the borers had died in the soil. 
