352 



INSECTS AFFECTING VEGETATION 



To follow the same crops with each other continuously in- 

 creases the facilities for the depredation of insect pests attacking 

 these crops. Not only is an intelligent rotation essential in farm 

 practice, but the winter season should be well provided for. When 

 we leave a corn field undisturbed after harvest, allowing the stubble 

 to remain intact till the following spring, we should not be surprised 

 when our crop the following year is seriously injured by corn stalk 

 borer, corn earworm, or corn billbugs. In view of these considera- 

 tions and with the available records about the habits, life histories 

 and food plants the following plan of rotation and cultivation is 

 proposed. Only the general principle can be laid down in this 

 bulletin and each farmer must vary it as the situation may suggest. 

 (Bui. 150 S. Car. Agr. Exp. Sta.) 



Plots. 



First Year. 



Second Year. 



Third Year. 



t Vetch seed may be mixed with the rye. 



In the above table rye is given as a winter cover crop except 

 where oats is used in the rotation, this being chiefly for a section 

 where no systematic rotation has been practiced, rye being a safe 

 crop for the beginning. Where crimson clover or other clovers 

 can be grown these may be substituted for the rye and cowpeas. 

 Before using these in a regular rotation, however, the planter should 

 become familiar with the methods for growing them in order to 

 avoid as far as possible any necessity of letting the fields lie exposed 

 during the winter. 



To get a rotation perfect for controlling all field crop insects 

 is impossible because in some cases one and the same pest may 

 be an enemy to two of the main crops used. In a rotation con- 

 sisting of cotton, corn and oats as the principal crops it is impossible 

 to avoid cotton and corn following each other. This is unfortunate 

 owing to the ravages caused by root lice and wire-worms, though 

 entirely advantageous in cases where nematodes of cotton (root 

 knot) are to be combatted, corn being no important food plant of 

 these worms. In the rotation where cotton and corn follow each 

 other they are separated by rye, which is not a food plant for estab- 

 lished corn and cotton pests, at the same time being a good cover 

 crop involving clean culture and a consequent elimination of weeds 

 serving as winter host plants of the insect enemies. This will also 

 tend to eliminate injury from corn earworm and cotton boll worm, 



