Insect sterilization methods

Several methods have been proposed for the practical application of insect sterilants, such as contact, oral ingestion and sterile male release method. This latter method involves capture of the males, their chemosterilisation and subsequent release which means considerable excess of work compared to the usual application of pesticides. Nevertheless it seems particularly advantageous because under appropriate conditions it permits almost complete control of undesirable insect populations in several generations. 

Masner, P., Slama, K., Zd arek, J., and Landa, V. (1970), Natural and synthetic materials with insect hormone activity. X. A method of sexually spread insect sterility, J. Econ. Entomol. 63, 706-710. 

White trap (White 1927) is one of the most common methods to produce entomopathogenic nematodes. Insects are inoculated with entomopathogenic nematodes on a petridish lined with filter paper. After 2-5 days, the infected insects are transferred to the White trap. The White trap consist of an inverted watch glass placed in a petridish on which Whatman paper of appropriate size is placed and moistened with sterilized distilled water. Adequate amount of distilled water is also maintained on and around the watch glass. As the infective juveniles emerge from the cadaver they migrate to the surrounding water and get trapped. The nematodes are harvested from the White trap and collected in a beaker. The concentration of nematodes can be accomplished by... 

More information must be available on the toxicity of the promising compounds before the full range of possible methods of application for the control of various species can be determined. Chemosterilants can certainly be used in the control of some species to sterilize reared insects for release among natural populations. No doubt they will also prove acceptable for use with various baits and attractants, which would bring them into contact only with the species... 

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. 

Construction of sex-linked genetic markers in major economic pests will facilitate expansion of genetic control methods such as the sterile insect technique and backcross sterility in Heliothis virescens. 

The thematic treatment in this book differs somewhat from that of other works on this subject, and thus may serve as a supplement to other books. Our object was not to write an encyclopedic work on pesticides and their characteristics. Rather, we discuss mainly those active substances in pesticides which are of practical significance, may be of possible future importance, or represent research results and interesting trends. With regard to the latter, compounds are also discussed which are not on the market but represent promising new types. Ample space has been devoted to alternative methods of plant protection, e.g., insect growth regulators, sterilants and pheromones, which show promise for control of insect pests. 

The most important ways of direct pheromone application are their combination with traps, and their joint application with insecticides, male sterilants or insect hormones on restricted parts of the area to be protected. This method of application permits a considerable reduction in the quantity of insecticide to be used which, besides its economical advantage, is important also from the aspect of environmental protection. 

Ionizing radiation has been used to control harmful insects. Captured males are sterilized by radiation and released to mate, thereby reducing the number of offspring. This method has been used to control the Mediterranean fruit fly in California and disease-causing insects, such as the tsetse fly and malarial mosquito, in other parts of the world. 

Standing advantages of the technique is that, unlike chemical methods, it becomes more efficient as the population of the pest is reduced because of the increasing ratio of radiation-sterilized insects to fertile ones. There are, however, the following requirements for a successful application of the technique ... 

Release of sterilized males. In this method very large numbers of, say, the male of the pest insect species are bred and are then sterilized by exposure to X- or 7-radiation. They are then introduced into the problem area in such numbers that there are far more of them than there are natural, fertile males, so that mating is much more likely to involve a sterile insect. As a result no offspring will be produced. Thus in time the population will decline and insects will no longer be a pest. 

Between 1952 and 1953, scientists of the U.S. Department of Agriculture conducted successful field experiments with a revolutionary method of insect control (Baumhover, 1966). The principle of this new technique was simple the reproductive capacity of an insect population is inversely related to the ratio between the sterile and fertile members of the popula-... 

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