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 pl anting. — In our Third Eeport 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 Eeport, 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 j 

 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 foT 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 he free from worms, while the other would have 

 from 50 to 60 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 

 com 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 

 will 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 be 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- 



* The wavy appearance of the shriveled husk is here alluded to. — C. V. R. 



