Uploaded by veronika.k

pesticides and herbicides

Pesticides and Herbicides
Pesticides are types of chemicals designed to kill 'pests.' Pests include all kinds of
insects, flying and creeping. They also include fungi and bacteria which attack plants and
trees. Pesticides include herbicides which are used on plants. They also include fungicides
which kill fungi. Miticides are used to kill mites. Rodenticides kill the many types of rodent
pests. Insecticides kill insects.
Pesticides can be in different forms. They can be liquid, powder or a gas. Ant traps and
rodent poisons are used to kill ants and rodents. Health experts are concerned about the
use of pesticides near edible plants. Toxic, harmful or poisonous, residue from these
pesticides may remain on the plants and pass on to people who eat the food.
The Environmental Protection Agency of the United States government keeps data
which show that toxic residue can pass to humans through food. A group called the
Environmental Working Group puts out each year a list of the twelve pesticides called the
'dirty dozen.' These are the most dangerous pesticides. They may leave a toxic residue.
Any kind of produce which is listed as organic does not contain toxic pesticides.
Insecticides are a type of pesticide. An insecticide can be a concentrate which is mixed
with water before spraying. It can be in liquid, granule or dust form also.
Herbicides are a type of pesticide. They are chemicals which are used to kill many
types of weeds. Some are selective. Some are non-selective. The selective herbicides
target a specific type of weed which is known to be doing the damage. Non-selective
herbicides are made to kill everything growing in one area. If a person wants no grass to
grow in his driveway, he might spray a non-selective herbicide.
Herbicides work several different ways. Some are sprayed on and are called contact
herbicides. Contact with a weed kills it. The problem is that every part of the weed
needs to be covered with the spray. Otherwise, the weed will regenerate. Systemic
herbicides get into the roots or leaves and travel to other parts of the plant. Preemergent herbicides will prevent seedlings from growing. It is put into the soil before
the plant appears.
In ancient times, ashes, common salts, and bittern were used as herbicides. Bittern is
a foul-tasting solution left after the salt has evaporated from brines or seawater. In the
Vietnam War during the 1960's and 1970's, the United States military used a combination
of chemicals to defoliate the jungle. It was called Agent Orange. This chemical was
used to clear the jungle of vegetation for the army so that they could be able to see the
enemy and move more easily. Because many serious health conditions were attributed to
exposure to this chemical, many chemical compounds have been reevaluated and not
used indiscriminately, that is used when not needed.
Use of the chemical in Agent Orange was prohibited in the United States in 1984.
Glyphosate was identified as an herbicide in 1970. It was originally sold under the name
Roundup. It was not very toxic or harmful and disappeared quickly into the environment.
Since the 1990's, some crops have become resistant to this herbicide. Superweeds have
grown up which are resistant to glyphosate.
Vinegar and herbicidal soap can be used as a natural herbicide. However, even a
natural herbicide may harm a plant a person wants to protect. Garlic and red pepper
sprays can be used also. The choice depends on what a person wants to kill.
00 : 00 : 08
1) Which of the following is the meaning of the word toxic?
A: Beneficial
B: Clean
C: Useful
D: Harmful
2) Which of the following is the word used on produce to tell that no toxic chemicals were used during
its growth?
A: Inorganic
B: Natural
C: Organic
D: Fresh
3) Which of the following is the word which means to get rid of vegetation?
A: Defoliate
B: Fertilize
C: Revitalize
D: Contaminate
4) Which of the following is the name of the governmental division which distributes data telling how
toxic residue can pass on to people through food?
A: Environmental Division of the United States
B: Chemical department of the United States
C: Environmental Protection Agency
D: Chemical Examination Department
5) What is the meaning of the phrase 'Agent Orange'?
A: Secret agents who wear orange clothes
B: A type of orange
C: A chemical sprayed in Vietnam
D: A person who picks oranges
6) Which of the following is the chemical herbicide originally sold as Roundup?
A: Glycogen
B: Glysomin
C: Glyminate
D: Glysophate