state College, Miss. , have demonstrated that sterile male boll weevils under cage and 

 field conditions do exert a depressing effect on the reproductive potential of normal 

 populations, and the elimination of low-level isolated populations has been achieved by 

 high ratios of sterile to fertile males. 



The foregoing discussion considers the role that sterile male boll weevils might 

 play in eradication, if it is necessary to reduce the natural population to the maximum 

 extent possible before using sterile insects. However, it is the writer's view that 

 sterile male boll weevils might be employed more efficiently if their use is properly 

 integrated with a minimum number of insecticide applications. Based on studies of 

 various hypothetical models, it is estimated that the use of reasonably competitive, 

 sterile, male boll weevils would be the most economical, and no doubt also the most 

 desirable, way to eliminate populations when the natural population has been reduced to 

 the order of 10 insects per acre. 



There are several ways, theoretically, whereby the use of insecticide treatments 

 and sterile male boll weevils could be integrated to achieve total population control. A 

 number of possibilities have been studied, but the system that seems especially 

 encouraging is to reduce the overwintered population by inaugurating an intensive 

 insecticide program, either in the fall or spring, and then to release sterile insects. 

 If sterile boll weevils, mating with boll weevils emerging in the spring, would preempt 

 other matings, an insecticide program in the fall should be satisfactory. If treatments 

 were made in the fall, sterile males would be released at squaring time, possibly after 

 one insecticide treatment. An intensive cultural program in the fall and through the 

 winter, followed by the release of sterile males, might be the most desirable procedure 

 for study in south Texas. 



As discussed earlier, it seems that an adequate number of properly timed insecti- 

 cide treatments during the spring period could be expected to reduce the overwintered 

 population by 95 percent. For the purposes of this report, a spring treatment program, 

 followed by the release of sterile males, will be considered. A proposed integrated 

 program of insecticide applications and sterile male releases is shown in model 8, The 

 model assumes six insecticide treatments at 5-day intervals in the spring, beginning 

 when the first squares appear, in order to reduce the population, as well as reproduction 

 in the parent generation, by 95 percent. We could expect a normal, uncontrolled parent 

 population of 200 boll weevils per acre to increase to 1, 000 per acre for the F^ genera- 

 tion. This would amount to an average emergence rate of 50 boll weevils per day during 

 the F-^ emergence period. But, if we assume 95-percent control of reproduction by 

 virtue of the insecticide treatments, we could then assume an accumulative total of only 

 50 boll weevils in the F-^ generation, or an average of 2. 5 per day. 



It is proposed that 300 sterile males be released after the last of the six applica- 

 tions of insecticides, and maintained at that level for the 20-day F-^ emergence period. 

 The ratio of sterile to fertile insects can be expected to be higher during the early part 

 of the F, emergence period than near the termination because of the accumulation of 

 normal males during this 20-day period. 



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