Biological Controls, Part 1 living, protect, farmers, controls, English

李武军

This is Steve Ember with the VOA Special English Agriculture Report.
Biological controls are living things that eat organisms harmful to crops. They offer new ways for farmers to grow organic crops and protect the environment.
In modern times, farmers have depended on chemicals to kill harmful insects, plants and other organisms. But, many scientists and farmers are looking for ways to grow crops without using poisons. Limiting chemicals can save farmers money as well. One way to avoid using poisons is to release helpful insects that are natural enemies of harmful insects, or pests.
Some insects eat pests. The lady beetle, or ladybug, is well known. Round, colorful lady beetles eat many kinds of harmful insects including aphids. Aphids develop colonies and eat plant fluids.
An adult lady beetle can eat fifty or more aphids a day. Aphids attack many different kinds of crops. This makes lady beetles a good defense against aphids for growers of fruit, grains, beans, strawberries and other crops. Lady beetles live in Asia, Europe and the Americas. Farmers can buy them from suppliers.
Some insects inject their eggs inside the bodies of pests. These are called parasitoids. Young parasitoids come out of their eggs and eat the pests. Some parasitoids can be very effective. They keep the pests from reproducing. After they become adults, they lay many eggs on other pests.
A tiny wasp with a big name is a good example. Encarsia formosa is used all over the world for vegetables and flowers grown indoors.
The Encarsia formosa wasp injects eggs into the bodies of young white flies. There are many different kinds of white fly pests and E formosa likes to eat at least fifteen of them. Some of these wasps can lay enough eggs to kill ninety-five young white flies in twelve days. E. formosa is most popular in Russia and Europe.
The United States Department of Agriculture has been studying a fly that attacks another pest - the fire ant. The phorid fly attacks fire ants in the same way as E. formosa. Phorid flies kill only about three percent of the ants in a colony. But they greatly damage the colony's ability to collect food. The U.S.D.A. has released phorid flies in an effort to control fire ants in the southeastern United States.
Next week, we tell about two kinds of biological controls that attack pests in new ways.
This VOA Special English Agriculture Report was written by Mario Ritter. This is Steve Ember.