\ 



320 



620. ; Jenkins, J. N.; Parrott, W. L.; and Euford, W. T. 1969. Factors 



contributing to resistance and susceptibility of cotton and other hosts 

 to the boll weevil, Anthonomus grandis . Entoraol. Exp. Appl. 12: 801-810. 

 A large portion of the world's germ plasm of cotton has been screened at the 

 USDA Boll Weevil Research Laboratory, State College, Mississippi during the 

 period 1962-68 utilizing developed techniques. An oviposition suppression 

 factor causing 25-40% reduction in number of eggs laid by the weevil has been 

 found in Gossypium barbadense and successfully moved into upland cotton, G^. 

 hirsutum . Two years field data with frego cottons indicate that the frego 

 character contributes a significant degree of non-preference for egg laying 

 by the boll weevil under field conditions. The frego character is currently 

 being combined with selected lines of G. htrsutum carrying the oviposition 

 suppression factor. A seedling screening technique utilizing field cages and 

 greenhouse sand flats has been shown to have significant value in screening 

 for individual resistant plants within a commercial variety. A number of 

 selections with 25% or more resistance to oviposition are under extensive 

 investigation. A number of biologically active materials have been detected 

 in the cotton plant and other hosts of the boll weevil which significantly 

 influences feeding stimulation, feeding deterrency, repillency and attractancy 

 of' the weevil to its hosts. A highly active square abscission factor has been 

 detected and extracted successfully from 2nd and 3rd instar larvae. The 

 material injected into cotton squares causes 95% abscieii-on of squares within 

 A8-60 hours. 



621. ; Lafever, H. N. ; and Jenkins, J. N. 1966. Influence of the glandless 

 genes in cotton on feeding, oviposition, and development of the boll 

 weevil in the laboratory. J. Econ. Entomol. 59: 585-588. 

 In feeding tests boll weevils, Anthonomus grandis Boheman, fed significantly less 

 on the glandless cotton lines Acala 4-42-77 GS, Atlas 182 GS, DPSL GS, Stardel GS, 



