2004-4-12
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.