378 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
the plant which is removed in the process of topping is so small pro- 
portionally that their destruction will not pay for the labor expended. 
With corn, topping might occasionally be of some avail, as it tends to 
hasten the maturing of the ears, rendering them distasteful to the worms. 
Any one who has read the long and varied list of food-plants which 
we have already given will at once see the objection to the adoption 
of rotation of crops as a remedy. With food-plants so numerous, a 
cessation in the growth of one of them, even though it were the prin- 
cipal one, could make no very important difference in the numbers of 
the Boll Worms. Still many writers have urged this as a sure prevent- 
ive, and it is a curious fact that a correspondent of the Southern Culti- 
vator a number of years ago proposed corn as a most excellent crop to 
rotate with cotton, never suspecting the identity of the Corn and Boll 
Worms. 
Early planting. — In our Third Report on the Insects of Missouri, 
we expressed the opinion that corn planted very early and very late is 
more apt to be badly infested than that planted moderately early and 
moderately late, the early -planted crop being infested by the first brood 
and the late by the second brood. Professor French, however, in the 
Seventh Illinois Entomological Report, has detailed a contrary expe- 
rience, in which late-planted corn fared badly while the early crop es- 
caped. In a bad worm year our rule would undoubtedly hold good ; 
but in an ordinary season,' if the corn is planted early and forced to 
early maturity, the ears will have become hard before the second brood 
has made its appearance, the first brood not being sufficiently numer- 
ous to do any marked damage. 
Low corn vs. high corn. — In the Pacific Rural Press for September 
13, 1879, Professor French put forth the following idea: 
I have found for the past two years that where there were two varieties of corn 
growing near each other, the one tall, with ears five or six feet from the ground, and 
the other short, the tall corn would be free from worms, while the other would have 
from 50 to GO per cent, of the ears waving.* Where the tall corn has been growing by 
itself there are usually some worms in the ears, but not so many as in fields of a low 
variety. The reason of this seems to be in the fact that the parent moth does not fly 
above 3 or 4 feet high if it can find suitable places for depositing the eggs. Probably 
every one familiar with the moth has noticed that when disturbed or drawn from its 
retreat in the day-time, the moth starts up from some place not more than 2 or 3 
feet from the ground. Now it is evident from these points that if a kind of sweet 
corn can be had growing tall enough so that its ears shall be, say, 5 feet from the 
ground, and small patches of some low-growing kind be planted near this, the tall kind 
vfill be unmolested while the eggs will be deposited in the ears of the low variety, 
thus securing corn for the market without worms. The low kind, while not fit for 
market, need not bo a perfect loss, for it can be fed to stock, probably being worth 
enough for that use to pay for its culture. 
Fall plowing. — In those localities where the temperature falls low 
enough every winter to freeze the ground to the depth of six inches, or 
even less, late fall plowing will undoubtedly destroy most of the hiber- 
*Tho wavy appearance of the shriveled busk is here alluded to. — C. V. K. 
