Sterile insect release techniques

Genetic Control. Some Insect pests have been successfully controlled by releasing sterile Insect males in sufficient quantity so that the pest population cannot reproduce. This has proven particularly effective in the control of the screwworm fly, a major pest of cattle (33). Genetic engineers may be able to provide other genetic techniques that will enhance the control of crop pests (34). 

There have been two main lines of development in the control of insects by irradiation firstly, the disinfestation of stored products at doses sufficient to prevent reproduction of the insect, and secondly, eradication of insects in the field by the technique of sterile male release. Both lines of approach have achieved success, a plant for the disinfestation of grain being under construction in Turkey at this time, whereas in the United States, success in the elimination of the screw-worm fly has been achieved, and recently it has been announced that control of fruit flies can be effected in this way. 

Genetic Control. Manipulation of the mechanisms of inheritance of the insect pest populations has occurred most successfully through the mass release of sterilized males, but a variety of other techniques have been studied, including the environmental use of chemosterilants and the mass introduction of deleterious mutations, eg, conditional lethals and chromosomal translocations (58 ndash 60) (see GENETIC ENGINEERING). 

Sterile Males— Males of some pest insect species may be reared and sterilized in laboratories and released in large numbers into infested areas to mate with native females. These matings produce infertile eggs or sterile offspring and help reduce the pest population. This technique has been used successfully in only a few species and is still being developed. The screw worm, which attacks cattle, is one insect on which this technique has been effective. 

Radiation doses of ss 80 J/kg have been used to sterilize the males of insect species, which are released after sterilization and mate with females. In this way, further reproduction of the species is reduced or prevented. The technique has been applied in the USA, Mexico, Egypt, Libya and other countries to eradicate screw-worm flies and other insect species that are threats to agriculture. 

Some forms of pest resistance involve. hanging the pest rather than the host plant. The best example of autocidal resistance is the sterile male technique used to control. nsects. Scientists rear thousands of males of a particular insect species under controlled conditions, then sterilize them with x-rays. These sterilized males are released in the wild to mate with females of the same species. Since the males are sterile, mated females do not produce eggs, causing populations to drop drastically over time. (The technique is restricted to insect species with females that only mate once.) This method is most successful when the sterile males compete aggressively with the natural population of fertile males. A working example of autocidal resistance occurs at the border of Mexico and California, where sterile males of the Mexican fruit fly are released to help control populations and to prevent the pests from entering California. 

Radiation has been used to sterilize (80 Sv) the males of certain insect species which when released (the ratio between the sterilized and untreated males was approximately 4 1), mate with females and prevent further reproduction of the species. This technique has been used in the US, Mexico, Egypt, Libya, etc to eradicate screw worm flies which can cause huge damage to the cattle industry. The technique is now also used against other insect species which are threats to agriculture. 

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