As a result of basic studies on the diapause phenomenon in the boll weevil by 

 J. R. Brazzel and L. D. Newsom of Louisiana State University, prehibernation control 

 has been given more attention. Cooperative research by Texas A. & M. College and 

 the Entomology Research Division, which was carried out by J. R. Brazzel and 

 T. B, Davich, has shown that about four properly timed insecticide treatments in the 

 fall can also be expected to reduce the prehibernating population by about 90 percent. 

 The writer has estimated (unpublished report) that by applying about seven insecticide 

 treatments, properly timed to provide maximum kill of both reproducing and diapausing 

 boll weevils in the fall season, the hibernating population could probably be reduced by 

 95 percent or more. Results of field experiments conducted by investigators at the 

 boll weevil research laboratory at Stoneville, Miss, indicate that this is a conserva- 

 tive estimate. It is believed, therefore, that by combining a fall- and a spring- 

 treatment program, it would be economically feasible to reduce a normal population to 

 less than one boll weevil per acre. The combined effect of two separate control pro- 

 grams, each 95-percent effective, would theoretically reduce the population by 99. 75 

 percent, or one boll weevil on two acres of cotton, if 200 boll weevils per acre is 

 representative of a normal, uncontrolled, spring population. 



In an unpublished report on the population dynamics and control of the boll weevil 

 prepared in 1959, the writer advanced the hypothesis that 95-percent control of 

 prehibernating boll weevils in the fall, and a similar degree of control in the spring, 

 should virtually eliminate populations of the pest in many situations. As research 

 advances, this appraisal seems more and more realistic. At least it seems reasonable 

 to believe that it would be possible and practical, with available materials and methods, 

 to reduce boll weevil populations to levels of a few insects per acre. In such event, an 

 overwhelming ratio of sterile to fertile insects could be achieved by releasing only a 

 few hundred sterile insects per acre. 



A field experiment is underway by T. B, Davich and M. E, Merkl of the Boll 

 Weevil Research Laboratory at State College, Miss. , to determine to what extent a 

 boll weevil population can be reduced by an intensive and combined fall and spring 

 insecticide-treatment regime. Such effort has never been made to determine, on an 

 isolated population, what effect such a combined program will have on the total popu- 

 lation. Even if the estimated 95-percent levels of control cannot be achieved under 

 operational conditions by each of the two series of treatments, it is believed that at 

 least 90-percent control of the population can be achieved by an insecticide-treatment 

 regime in the fall and a like percentage in the spring. This would reduce the population 

 by 99 percent during the period of greatest scarcity for the insect. If 200 boll weevils 

 per acre is representative of a normal surviving spring population, 99-percent control 

 should reduce the number to two boll weevils per acre. The elimination of such low- 

 level populations by further use of insecticides would probably require at least as many 

 treatments as were required to eliminate the first 99 percent. However, the sterile- 

 insect-release method, if perfected, should provide a more economical and more 

 desirable method for final elimination of such low populations. This line of reasoning 

 has been the basis for the writer's proposal that the sterile-insect technique could play 

 an important role in boll weevil eradication. 



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