19 



the average number on various portions of the plant; also the aver- 

 age number of larvae per plant and their approximate sizes. 



Table II. — Average number of hollworm eggs and larvw on corn trap crop. 



Viewing the trap-crop idea superficially it might appear that the 

 increase of boUworms would be favored by supplying their favorite 

 food. This, however, is not the case. The concentration of the eggs 

 upon the corn results in their destruction in large numbers by para- 

 sites an 1 predaceous enemies which are attracted by the abundance of 

 food and favorable breeding places furnished them in the form of 

 bollworm eggs and larvae. It is seldom that more than 1 or 2 of the 

 15 to 30 larvae which usually hatch in the fresh silk of an ear of corn 

 ever attain full growth on account of their cannibalistic habits. 



The mistake of planting belts of corn through or around a cotton 

 field at the usual time of planting corn in the spring is of quite com- 

 mon occurrence. Instead of this acting as a trap, as is desired, it is 

 really detrimental, as the corn furnishes a favorable breeding place 

 for the larvae during the early summer and becomes hard about the 

 1st of August, thus forcing the moths of the third generation to seek 

 other places for oviposition. 



With favorable weather conditions and fair cultivation corn planted 

 the last of May or 1st of June will be in silk and tassel by August 1. 

 Cowpeas planted about ten days later will be in full bloom about 

 that date. Mexican June corn is usually preferable for late planting, 

 owing to its larger root system and consequent greater ability to with- 

 stand drought. 



The trap-crop system will give best results if generallj^^ adopted by 

 the farmers in each locality. On large plantations the planting of 

 small areas of corn here and there in the fields is practicable. Such 

 early crops as potatoes, oats, or wheat may be followed by corn and 

 cowpeas with practically the same results. 



The corn may be harvested in the usual way, and the peas either 

 harvested or plowed under. Mention should be made of the benefit 

 exerted upon the soil by the growing of cowpeas or other plants of 

 this class. 



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