a chemical substance that produces sterility and is used to control insect pests by causing genetic and functional changes in the organism.

Chemosterilants are divided into three groups: antimetabolites, alkylating agents, and a miscellaneous group of substances. Antimetabolites, such as methotrexate, aminopterin, and fluorouracil, upon introduction into the organism, replace the normal metabolites in metabolic reactions and disrupt the synthesis of DNA and RNA in the nuclei of reproductive cells, thus causing sterility mainly in females. Alkylating agents, such as chlorambucil, apholate, and aphoxide and its structural analogs me-TEPA and thio-TEPA, cause chromosomal damage in reproductive cells (involving multiple linkages and breakages), leading to sterility mainly in males. The miscellaneous group includes triazine-type herbicides, xylohydroquinone, some antibiotics, alkaloids, and certain insect hormone analogs.

Insects are sterilized by direct application of microscopic amounts of the chemosterilant to the insect itself (contact action) or by the consumption of treated food. Very simple devices, such as cuvettes, cylinders, and boxes, are used for these purposes. A sponge or a piece of gauze impregnated with a special solution containing nutrients, such as sugar or syrups, and chemosterilants and insect attractants (compounds with a specific odor) is placed in these devices. The sterilized insects are then released in areas of extensive infestation. The eggs produced after a sterile male mates with a nonsterile female, and vice versa, are infertile.

The study and practical application of individual chemosterilants were begun in the USSR, Czechoslovakia, USA, Japan, and Great Britain in the 1950’s. For example, the addition of 5-fluorouracil and a 0.05–0.1 percent solution of aminopterin and its sodium salt to food was found to be effective against the housefly. Chemosterilants are used in the USA to control the screwworm fly, the chief cattle pest; special facilities have been constructed to produce and sterilize the insects. Chemosterilants are also used against fruit flies, tsetse flies, stable flies, malarial and other blood-sucking mosquitoes, cockroaches, coddling moths, and citrus red mites and other arthropod pests. Many antimetabolites, alkylating agents, herbicides, and other chemosterilants have been found to be toxic to man and to beneficial animals.

In the 1960’s, scientists in Czechoslovakia, Great Britain, the Federal Republic of Germany, Japan, and some other countries succeeded in synthesizing hormones that regulate insect development. They also obtained compounds similar in chemical structure to the juvenile hormone, which regulates metamorphosis, and the ecdysial hormone, which regulates shedding. Especially promising are analogs of the juvenile hormone, which have contact action specific for certain insects and which are effective in minute doses (10–100 g per 1 hectare). These agents are not harmful to birds, mammals, humans, and plants.

Sterilization methods are more efficient when used in conjunction with other methods of insect control, such as the prior use of insecticides to reduce insect population.