3. There was a difference in mortality from 5 pure compounds as the 

 season progressed. 



4. Phosphorus compounds •were more effective than chlorinated hydro- 

 carbon using topical applications. 



1957 - Fye, R. E., R. L. Walker, and A. R. Hopkins. Susceptibility of the boll weevil in 

 South Carolina to several insecticides. J. Econ. Ent. 50(5):700-701. bi-m. 



Results from topical applications indicated a varying susceptibility of South 

 Carolina boll weevils to chlorinated hydrocarbons. Median lethal doses of the 

 insecticides used in boll weevil control correlated fairly well with recommended 

 field dosages. Seasonal variations, nutritional and source differences, and dif- 

 ferences in mode of action of the various insecticides were apparent. 



One Darlington County location where large amounts of insecticides are used 

 showed a high weevil resistance to endrin, but the area is still apparently well 

 defined. Weevils with the greatest susceptibility to endrin were from Georgetown 

 County where little insecticide is used. Little variation in susceptibility to 

 Guthion was noted in weevils from various parts of South Carolina. 



1957 - Hamner, A. L., and R. E. Hutchins. Boll weevil resistance to poison. Miss. 

 Farm Res. 20(1):1, 5. Jan. 



It was concluded that definite resistance exists to some degree, probably 

 over relatively large areas in some parts of the State and perhaps on individual 

 farms in other areas, particularly in the higher areas. Information indicates that 

 resistant strains are associated with large numbers of applications each year 

 over a period of years. 



Field weevils were brought into the laboratory. Micro pipette was used for 

 the measured drop method. 



1957 - Roussel, J. S., and D. F„ Clower. Resistance to the chlorinated hydrocarbon 



insecticides in the boll weevil. J. Econ. Ent. 50(4):463-468.' 



Results of studies conducted during 1955 and 1956 demonstrated that boll 

 weevil populations resistant to the chlorinated hydrocarbon insecticides exist 

 in Louisiana. Field experiments showed that resistance began to appear in 1953. 

 It was determined that resistance was in the order of 100-fold and had persisted 

 in the 1956 population. The fact that resistance persisted in 1956 would indicate 

 that it is genetically controlled. A 2-fold vigor tolerance is demonstrated for 

 Guthion. Some vigor tolerance is noted for calcium arsenate and Phosdrin in cage 

 tests. 



1958 - Tippins, H. H., J. J. Paul, L. W. Morgan, and C. M. Beckham. Results of 



laboratory studies on the toxicity of several insecticides to the boll weevil in 

 Georgia. Ga. Agr. Expt. Sta., Mimeo Series, n. s. 53. March. 



Field collected weevils were used. Topical applications were employed, 

 using BHC and Guthion. Although differences in susceptibility between populations 

 were shown, they were probably due to such factors as laboratory technique, 

 collection date, or seasonal resistance. Differences were quite small, as 

 compared with those of 100-fold as reported for chlorinated hydrocarbons by 

 workers in other States. Where comparing percentage mortalities, the dif- 

 ferences in susceptibility to Guthion were slightly larger than BHC in the work 

 at Experiment. 



1958 - Walker, J. K. Jr. Control of boll weevils resistant to chlorinated hydrocarbon 

 insecticides. Tex. Agr. Expt. Sta., Prog. Rpt. 2009. Feb. 13. 



Insecticide evaluations were made in 2 areas of the Brazos River Valley in 

 1957, one where weevils were reported as resistant and another area where 

 resistance had not been found. 



In the non-resistant area toxaphene-DDT was as effective as Guthion, methyl 

 parathion and malathion. In the resistant area several organic phosphorus com- 

 pounds, Sevin and calcium arsenate were more effective than toxaphene-DDT. 



152 



