456 FIELD CROPS 



what similar to flax wilt. The fungus enters the young 

 plant through the root hairs, and its mycelium fills the cells 

 of the plant, preventing it from obtaining water. The plants 

 become dwarfed, turn yellow, and usually die. As in flax, 

 certain plants seem to be resistant to the disease. If seed is 

 saved from these, resistant strains may be produced. This 

 disease is confined to the southeastern part of the cotton 

 belt. In Texas, particularly on the heavier lands, root rot 

 is common. This disease attacks the roots of all tap-rooted 

 plants, including cotton, the legumes, and many kinds of 

 fruit trees. The most effective remedies in cotton fields 

 are rotation of crops and deep fall plowing. The disease 

 does not affect corn, the small grains, or grasses. 



624. Insect Pests. The most important insects which 

 attack the cotton crop are the boll weevil and the boll- 

 worm, though a host of others do more or less damage. The 

 boll weevil was first reported in extreme southern Texas in 

 1892, though it had been known in Mexico for many years. 

 Since then it has spread through the cotton belt steadily, 

 the advance northward and eastward being at the rate of 

 from forty to fifty miles a year. It is now spread over the 

 greater part of the cotton-producing area. 



The boll weevil is a grayish or reddish-brown insect about 

 one fourth of an inch long which lays its eggs in the squares 

 soon after the blossoms fall. The egg hatches and the 

 rapidly growing larva eats the contents of the young boll. 

 In about ten days, it turns into a pupa and a few days later 

 emerges as a weevil. This insect, when it first appears in a 

 district, is very destructive to the cotton crop, but its ravages 

 decrease as farmers learn better how to control it. The most 

 effective methods are. the rotation of crops, frequent culti- 

 vation to knock off and bury the infested squares, and the 

 early planting of early varieties, as the insects do not become 

 numerous till late in the season. As the weevil gets its 

 food from within, it is not easily reached by poisons applied 



