Pest-Destroyer

The worst U.S. crop pests are immigrants. The U.S. Department of Agriculture is usually quick to import the enemies of each new pest, but to adapt these delicate and specialized creatures to life in a new country often takes time. And if the wrong enemy is brought in, the cure may be worse than the disease.*

Last week the department announced that one of the worst crop-eating insects, the European corn borer, has neared the end of its reign of terror in U.S. cornfields. Its conqueror: a fly named Lydella stabulans grisescens, which is mainly responsible for reducing the losses from corn borers from $353 million in 1949 to $85 million in 1950. This year, the department predicts, the losses will be even lower.

Lydella does no harm to crops and attacks no insect except the corn borer. The females tenderly place their infant maggots at the entrances of the corn borers' tunnels. Then the maggots, guided by the peculiar genius of their kind, crawl into the tunnels, find the borers and destroy them by devouring their innards.

*English sparrows, introduced in 1850 to eat caterpillars, soon became a pest themselves.

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