In 1962, Rachel Carson's best-seller book, ''Silent Spring,'' helped arouse a new awareness of the effects of chemicals on the environment. Among other things , she criticized the chemical being used to try to eradicate the fire ant - a tenacious critter with a stinging bite and mixed effects on crops.
Use of the chemical, dieldrin, and its controversial successor, mirex, was eventually halted. But not the fire ant. It has continued to spread across most of the South and, according to some experts, could eventually go farther up the East Coast and even across country to California.
Today, a new plan to fight the fire ant - with a form of mirex - has environmentalists locked in a battle against the State of Mississippi and the Environmental Protection Agency (EPA).
In September the EPA granted an emergency permit for Mississippi, Texas, and Arkansas to use ferriamicide, a form of mirex. Four environmental organizations, the Audubon Society, the Environmental Defense Fund, the Sierra Club, and the National Wildlife Federation, have gone to court to try to block its use.
In the face of this opposition, in early December all three states withdrew their requests for emergency approval. But the states still want eventual use of the pesticide. C. M. Uelthschey, director of the state's fire ant control program, says when in ''battle'' sometimes you have to ''back off and regroup.'' He wants a full public hearing on the pesticide and further tests to prove it is safe and merits a permanent approval from the EPA.
Several new alternatives are being developed. One of them, being researched by University of Georgia entomologist David Fletcher, would use a chemical produced by the ants themselves to curtail their reproduction. But commercial production is years away. Another, soon to be on the market, was developed by the United States Department of Agriculture with a private company and, according to Donald Weidhaas, a USDA entomologist, it ''looks like it has promise'' without the controversial side effects of mirex.
Dr. Weidhaas says mirex causes cancer in laboratory animals and has killed juvenile shrimp and crabs in laboratory tests. But, he says, he knows of no tests proving that such effects occur in the field. The tests were ''inconclusive one way or the other,'' he says.
Use of mirex was halted several years ago under an agreement between the EPA and the pesticide's sole manufacturer. Halting its use was seen as a way to open doors for development of safer pesticides, says Thomas McGarity, a former EPA official who participated in the negotiations over mirex. If it comes back, ''We're back to square zero again,'' says Mr. McGarity, now a law professor at the University of Texas.
But Mississippi has seen a steady spread of the fire ant, according to one official there. State officials contend use of ferriamicide would be much cheaper than alternatives now on the market.
Ferriamicide degrades into harmless substances, Mississippi officials contend - a point disputed by environmentalists. It breaks down into kepone, a pesticide now banned by the EPA, and photomirex, which is ''at least as toxic . . . and perhaps more so'' than mirex, former EPA official McGarity says.
Whatever control method is used, an Alabama entomologist long familiar with fire ants urges moderation.
Though the fire ant causes some damage to certain field crops, it also feeds on insects that damage cotton and harm cattle, says Kirby Hays. It helps aerate fields, too, with its mound building, he says.