Passage 3For as long as humans have raised crops as a source of food and other products, insects hav
For as long as humans have raised crops as a source of food and other products, insects have damaged them. Between 1870 and 1880, locusts ate millions of dollars worth of crops in the Mississippi Valley. Today in the United States the cotton boll weevil damages about 300 million dollars worth of crops each year. Additional millions are lost each year to the appetites of other plant-eating insects. Some of these are corn borers, gypsy moths, potato beetles, and Japanese beetles.
In modern times, many powerful insecticides have been used in an attempt to destroy insects that damage crops and trees. Some kinds of insecticides, when carefully used, have worked well. Yet the same insecticides have caused some unexpected problems. In one large area, an insecticide was used against Japanese beetles, which eat almost any kind of flower or leaf. Shortly afterward, the number of corn borers almost doubled. As intended, the insecticide had killed many Japanese beetles. But it had killed many of the insect enemies of the corn borer as well.
In another case, an insecticide was used in Louisiana to kill the troublesome fire ant. The insecticide did not kill many fire ants. It did kill several small animals. It also killed some insect enemies of the sugarcane borer, a much more destructive pest than the fire ants. As a result, the number of sugarcane borers increased and severely damaged the sugarcane crop.
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