227 



under these field conditions may have measured a different component of preference 

 than our standard laboratory test for oviposition factors. In general, however, 

 lines selected in our laboratory test for low oviposition also showed reduced 

 oviposition in the field tests. A covariance analysis adjusted the number of 

 oviposition damaged squares for the number of oviposition damaged squares for 

 the number available to the weevil for oviposition. Gains in precision ranged 

 from 49 to 105% from the use of covariance. 



439. , and Parrott, W. L. 1971. Effectiveness of frego bract as a boll 



weevil resistance character in cotton. Crop Sci. 11: 739-743. 

 In 1970 four farms located in different parts of Mississippi each were planted 

 to 4 to 8 ha of cotton (Go ssypium hirsutum L.), homozygous for frego bract (fg 

 f g) , and to an approximately equivalent acreage of a non-f rego commercial 

 variety. Cottons with frego bract have shown resistance to boll weevils 

 ( Anthonomus grand is Boh.) when grown in small plots. Our 1970 tests were de- 

 signed to measure the cumulative effects of a frego-bract cotton, designated 

 M-64, on boll weevil populations when this cotton was grown in large acreages 

 and when the resistance was measured over three or four insect generations. 

 Results from these tests will be used to assess the role of cottons resistant 

 to boll weevil in an integrated approach designed to eradicate this insect. A 

 pilot scale boll weevil eradication program is now underway in Mississippi. 

 In the frego-bract cotton boll weevil oviposition, an indirect measure of 

 population, was suppressed 66, 71, 75, and 94% below that in the nonfrego varieties, 

 The variation in suppression was due to different numbers of overwintering weevils 

 and to various control measures used during the season. On two farms no insecti- 

 cides were required for boll weevil control in the frego-bract strain. The 

 frego-bract strain suppressed the population 94% on the farm with the smallest 

 number of overwintering weevils. Thus, oviposition suppression was greatest 

 where it can be of the most use in an eradication program. Fiber properties 





