51 



5 to 10%. However, removal of the auxiliary air-propelled spray component of 

 the system reduced its effectiveness by about 20%. This reduction was attri- 

 buted to the increased penetration of the insecticide into the plant canopy by 

 use of the auxiliary air. 



89. Brazzel, J. R. 1969. Environmental control measures used in plant pest 



control programs. In Proceed, of Tall Timbers Conf. on Environ. Pest Con. 

 Meas. 1968 Published by Tall Timbers Res. Sta., Tallahasee, Fla. , 1973, 

 . pp. 21-35. 

 The pink bullworm program in the southwestern United States is an example of 

 control by environmental management which has been practiced for many years. 

 This cotton pest diapauses in the larval stage in seed-cotton left in the 

 field at harvest. Cotton is the major host plant and populations which sur- 

 vive the winter on other hosts are negligible. Therefore, successful winter 

 survival is dependent to a great extent upon cultural practices in the field 

 during the off-season. Several agronomic practices have been adopted which 

 adversely affect the survival of the diapause larvae. These have the added 

 benefit of also being good farming practices. Immediately after harvest, 

 stalks and debris are shredded with a mechanical shredder which destroys the 

 food supply and may physically destroy up to 90 percent of the diapause larvae. 

 In the more southerly regions, the date for this host plant destruction is 

 set before the end of the normal growing season, thereby shortening the breed- 

 ing period during a growing season. This may prevent as much as one or more 

 generations in the fall when a large percentage of the population may diapause. 

 The boll weevil has been the major pest of cotton for approximately 75 years 

 in the southern cotton growing areas. Prior to the widespread use of the 

 synthetic insecticides in the 1940' s, control was based primarily upon cul- 

 tural practices. These control measures consisted of (1) early planting of 

 early maturing varieties, designed to produce as much cotton as possible before 



