Biocontrols（生物防除） are the way nature seeks balance. Consider the example of insects that attack crops. Other creatures eat these pests, unless natural controls are missing.

Biocontrols can also include organisms like worms and fungi. And they come in the form of bacteria and viruses. These are called pathogens（病原體）. A good example is a disease that affects Japanese beetles.

These beetles were accidentally brought to the United States almost one-hundred-years ago. They ate crops and spread out of control.

But in the nineteen-thirties, researchers discovered some young beetles infected with a condition known as milky disease. The researchers found the bacteria that caused this infection. They put it on the soil for other beetles to eat.

The government used hundreds of tons of the bacteria, called Bacillus popilliae (ba-SI-lus po-PILL-ee-eye). It controlled the Japanese beetles. But today it seems less effective. Another control may be needed.

Plants may also find themselves in a new home where they can reproduce quickly. The alligator weed native to South America is one such plant. It came to the United States and took over wetlands and rivers in several states in the South.

In nineteen-sixty-four, researchers released flea beetles in Florida. Flea beetles are also from South America. They like to eat alligator weed. The beetle solved the weed problem in central Florida. There was no need for further use of plant poisons. This case serves as a model of biological weed control.

There are three methods for biocontrol. One is conservation. Experts say this is probably the most important. Natural enemies of pests must be protected. This means to avoid treating crops with chemicals that will harm any helpful insects.

A second method is often called classical biological control. This means a helpful biocontrol is released to fight a pest problem. The release of ladybeetles to fight aphids on plants is another such example.

Finally, there is the method of biocontrol that experts call augmentation（增加）. Helpful organisms are added to fields to improve environmental balance.

Cornell University in Ithaca, New York, has a full Web site on biocontrol. You can find a link at our site, voaspecialenglish-dot-com. Or enter the words "Cornell" and "biocontrol" into a search engine on the Internet.

This VOA Special English Agriculture Report was written by Mario Ritter. This is Steve Ember.