^'TC ---pHJy *; ^; ***'*'^ ; *;^ 



328 



Approximately 95% control of overwintered weevils was obtained with the early- 

 season applications, resulting in approximately 88% control of F^ bo]l weevils. 

 When F2 boll weevils emerged, control declined steadily to 16% as migrants entered 

 the treated fields and depressed yields. The increase in boll weevils from the 

 overwintered to the peak late season population was 21-fold in untreated fields 

 and 856-fold in treated fields, indicating the magnitude of migration. Neverthe- 

 less, 6 insecticide applications increased the average yield of seed cotton 426 

 lb/acre. More than 1 bale/acre was produced in 29% of the treated fields and 

 in none of the untreated fields. 



634. , and Covington, B. M. 1969. End of squaring as an economic indicator 

 of approximate time to end insecticidal treatments for boll weevil 

 control. J. Econ. Entomol. 62: 35-36. 



Under various field conditions in North Carolina, cotton planted in mid-April 

 started squaring in mid- June, stopped squaring in mid-August or earlier, and did 

 not produce bolls which failed to open prior to the first fall freeze. Square 

 infestation by Anthonomus grandis Boheman was reduced and the yield of cotton was 

 economically increased by insecticidal treatments applied at approximately 5-day 

 intervals from the time the square infestation in July reached 10% until the end 

 of squaring. After the end of squaring, additional treatments applied at approxi- 

 mately 5-day intervals did not reduce the adult boll weevil population or increase 

 the yield of cotton. Hence, from the economic standpoint of cotton production, 

 the end of squaring (less than 1 square per linear ft of row) indicated the 

 approximate time to end insecticidal treatments for boll weevil control. 



635. ; Covington, B. M. ; and Smith, F. D. 1970. Effects of methyl parathion, 

 DDT, and toxaphene on the boll weevil, bollworm, and cotton plant in 

 North Carolina. J. Econ. Entomol. 63: 596-599. 



Toxaphene + DDT, methyl parathion + DDT, and toxaphene + DDT + methyl parathion 



\ 

 \ 



