38 COTTON 



are in force for the compulsory disinfection of all 

 cotton seed, and in Nyasaland and German East 

 Africa the importation of American seed has been 

 entirely prohibited. 



Cotton Boll-Worms. The American cotton boll- 

 worm (Chloridea obsoleta = Heliothis armiger), unlike 

 the boll-weevil, feeds not only on cotton, but on many 

 other plants, such as maize, peas, beans, tomatoes, 

 and tobacco. The eggs are usually laid on the under- 

 surface of the leaf. The larva or caterpillar emerges 

 in from two to seven days, and immediately begins 

 to feed near the place where it was^ hatched. In a 

 few days it reaches a boll, into whichlt bores. After 

 feeding on this, it migrates to another, and by con- 

 tinuing this course, causes great damage to the crop. 

 Growth is generally completed in about two or three 

 weeks, and the full-grown caterpillar is often as much 

 as ij inches in length. It now enters the ground 

 and becomes transformed into the chrysalis or pupa. 

 After about a month the moth emerges, and may 

 often be seen, especially in the evening, darting hither 

 and thither and seeking for a place to deposit its 

 eggs. The boll-worm has many natural enemies, 

 including several parasitic insects and certain bacterial 

 organisms. The woodpecker and other birds pick 

 out the caterpillars from infested maize ears and feed 

 on them. 



The pest is found in great numbers on maize plants, 

 and especially on the silky tassels and young ears. 

 When the tassels have passed their edible stage and 

 the maize has begun to harden, the moth seeks another 

 food-plant, such as young cotton. On this fact is 

 based the so-called " trap-crop " method of destroying 

 the insect. It consists in planting maize near the 

 cotton at a period sufficiently late to provide a supply 

 of tassels when the cotton boll is in danger of being 

 attacked by the pest. As soon as the eggs have been 

 deposited, the ears are gathered and destroyed. By 

 planting the maize at different times, several broods 

 of the insect may be trapped, and in this way the 

 pest may to some extent be kept in check. 



The use of poisons, especially Paris green and 



