32 



It will be noted that the acreage in peas, as compared with the acre- 

 age in cotton, decreases almost in proportion to the increase in sever- 

 it}^ of bollworm injury in the respective States. In Texas, where 

 there is but 1 acre in peas to every 205 acres in cotton, bollworm 

 injuries are of greatest severity. 



The very general practice of planting late corn for forage, silage, 

 and other purposes is, in effect, the application of the trap-crop idea. 

 By this practice, which has come about simply as a farm expedient, 

 the farmers of the Carolinas, Georgia, and portions of Alabama have 

 unconsciously greatly lessened the danger of bollworm injury to cot- 

 ton by providing the insect with a succession of its favorite food plant. 



RELATION OF WEATHER TO BOLLWORM INJURY. 



The belief is firmly established in the minds of many cotton planters 

 that rainy weather, especiall}^ during late Juh^ and earl}^ August, is 

 largely responsible for severe bollworm injury to cotton. Further, 

 the opinion is occasionally expressed that the "worm" is the direct 

 result of such weather conditions. The fact that it is just at this time 

 that the hardening of field corn forces the moths to the cotton fields 

 appears to be lost sight of, and the sudden and destructive appearance 

 of the larvae on cotton has often been attributed to the occasional 

 showers which ma}" occur at this time of year. However, a belief so 

 well established, resulting from many years of observation and expe- 

 rience, should have some foundation in fact, and such appears to be 

 the case. The accurate explanation of the factors involved, however, 

 is by no means easy, owing to the difficulty of obtaining data on a 

 question of this kind. 



As the reader will learn in the following pages of this bulletin, the 

 bollworms, upon completing, during July, their growth in the ears of 

 field corn, enter the soil and, after constructing a cell, become pupse, 

 from which, in the normal course of events, the moths or parent insects 

 issue about two weeks later. Observations have shown that many 

 of these pupal cells are not made with sufficient care by the larvse 

 to permit of the ready escape of the moth from the soil. The most 

 common defect is that the cell is not extended upward sufficiently 

 near the surface of the ground so that there will be but a thin crust of 

 earth for the moth to break through in making its escape. The occur- 

 rence of a soaking rain and the consequent softening of the soil would 

 permit the escape in perfect condition of man}^ moths which under 

 conditions of hard-baked soil must have perished in their pupal bur- 

 rows. It has often been observed in the course of this investigation 

 that moths were noticeabl}^ more abundant shortly after a soaking 

 rain. This fact probably has its explanation, as above intimated, in 



