Potentialities and Progress in the Development of Chemosterilants for Insect Control1

Abstract

The possible use of chemosterilants for insect control represents an extension of the sterility principle which involves the rearing and release of insects made sterile by exposure to gamma radiation, as was done in the eradication of the screw-worm fly ( Cochliomyia hominivorax (Coquerel)) on the island of Curacao and from the Southeastern United States. Certain chemical compounds, classed as alkylating agents, have been found to produce sterility in several species of insects including the house fly ( Musca domestica L.), Mexican fruit fly ( Anastrepha ludens (Loew)), and the stable fly ( Stomoxys calcitrans (L.)). Apholate (2,2,4,4,6,6-hexahydro-2, 2,4,4,6.6-hexakis(1-aziridinyl)-1,3,5,2, 4,6-triazatriphosphorine) and aphoxide (tris(1-aziridinyl) phosphine oxide) are among the most active chemosterilants currently under investigations. When administered orally or by contact these compounds produce irreversible sterility without apparent adverse effects on the mating behavior and length of life of the insects. Although chemosterilants may prove equally or more useful than gamma radiation in the production of sterility in insects for release, they offer possibilities for achieving sterility in the natural population if safe and effective ways of using them can be developed. If ways of producing sterility can be developed in the natural population it would not be necessary to rear insects. This procedure for applying the sterility principle offers several important ad vantages over the conventional method of killing insects. Insects that are sterilized cannot reproduce and thus such effect is equivalent to killing the insects. In addition, the sterile insects compete with the normal insects to further decrease chances for reproduction. This bonus effect represents the greatest advantage over the conventional way of controlling insect populations. In addition, however, sterile insects in the population are capable of limiting reproduction because of time and space effects, factors which are absent in the killing procedure. Figures are presented which show the theoretical effects on boll weevil ( Anthonomus grandis Boheman) populations which are subjected to control by an insecticide and by a sterility agent.