The Nature of Insecticides

Can Insects Be Eradicated?

Clay Lyle.

We know that insects have survived for 250 million years and that they are endowed with marvelous mechanisms by which they should be able to survive for many more years. We know also that no species of insect has disappeared from the earth because of man's activities, as have the dodo, the passenger pigeon, and some other animals. Yet I give an unqualified yes to the question, Can insects be eradicated?

It is possible to wipe out destructive insects and it is desirable to do so. When insects first migrate to a new locality they should be destroyed, while their numbers are still small, even at great expense, lest they continue to spread and cause losses to farmers that year and every succeeding year.

Several insects have been eradicated from such large areas that the complete extermination of their species throughout the world could probably be accomplished. It is true, though, that climate, natural enemies, food supply, and some other factors that affect any one species vary so greatly the world over that eradication might be practicable in one country and unimportant or impossible in another.

Three insects and one snail which had become well established in the United States have been eradicated and were not known to occur within our continental limits in the year 1952.

The Mediterranean fruit fly was exterminated from parts of 20 counties in Florida in about a year an outstanding example of eradication.

The parlatoria date scale was destroyed in several places in Arizona, California, and Texas.

The citrus blackfly was expelled from Key West, Fla., although fears of a reinfestation of the United States, from Mexico have been expressed.

The white garden snail has been eradicated from several counties in southern California.

Several other pests have been exterminated within definite areas, although they are still present in other sections of the United States or even in the same areas after reinfestation from outside sources. Among them are :

Pink bollworm, from northern Florida, Georgia, and large areas in Texas, New Mexico, Arizona, Oklahoma, and Louisiana, some of which have been re-infested from Mexico.

Sweetpotato weevil, from areas in several Southern States, which have since become reinfested.

Gypsy moth, entirely from Pennsylvania and New Jersey and greatly reduced in some other Eastern States.

Argentine ant, from several towns in Mississippi.

Citrus whitefly, from 16 counties in California; new infestations occurred after 1942 in 2 counties in California, but were eradicated by 1950.

Obscure scale, from Los Angeles and San Diego Counties, Calif.

Cattle tick, practically eradicated from the United States after a fight of more than 50 years. Effective methods of eradication were known before 1900 but could not be used successfully until the farmers of the South realized the importance of livestock production. The tick carries the protozoan organism that causes Texas fever.

Efforts to eradicate insects in other countries have also been successful in several instances.

The Colorado potato beetle first appeared in Europe in Germany in 1877. It was found again in 1887, 1914, and 1934. Each time it was promptly eradicated, but Germany, Belgium, the Netherlands, and Switzerland have since become infested through its spread from France, where it was first found in 1922. Infestations in England in 1901 and 1933 were quickly stopped. Reinfestations still occur in England as the beetle spreads over continental Europe.

The dangerous African mosquito (Anopheles gambiae), which caused 20,000 deaths in Brazil in 1938 and 130,000 in Egypt in 1943 by transmitting malaria, was apparently eradicated from Brazil by 1940 and from Egypt by the end of 1945. The Rockefeller Foundation assisted the governments of the two countries in the work. Large areas of Brazil have also been freed of the yellow-fever mosquito.

Sleeping sickness in sections of Africa is being reduced through the eradication of several species of tsetse flies (Glossing spp.) by chemical and cultural methods.

The brown-tail moth has been eradicated from Nova Scotia and New Brunswick; the gypsy moth from southern Quebec and New Brunswick; the codling moth from western Australia; and two species of cattle grubs (northern cattle grub and common cattle grub) from Clare Island, Ireland.

Sheep bot fly.