Pesticides is any chemical which is used by man to control pests. The
pests may be insects, plant diseases, fungi, weeds, nematodes, snails,
slugs, etc. Therefore, insecticides, fungicides, herbicides, etc., are all
types of pesticides
Another way to think about pesticides is to consider those that are
chemical pesticides or are derived from a common source or production
method. Other categories include biopesticides, antimicrobials, and pest
control devices.
Chemical Pesticides
Some examples of chemically-related pesticides follow. Other examples are
available in sources such as Recognition and Management of Pesticide
Poisonings.
Organophosphate Pesticides - These pesticides affect the
nervous system by disrupting the enzyme that regulates acetylcholine, a
neurotransmitter. Most organophosphates are insecticides. They were
developed during the early 19th century, but their effects on insects, which
are similar to their effects on humans, were discovered in 1932. Some are
very poisonous (they were used in World War II as nerve agents). However,
they usually are not persistent in the environment.
Carbamate Pesticides affect the nervous system by
disupting an enzyme that regulates acetylcholine, a neurotransmitter. The
enzyme effects are usually reversible. There are several subgroups within
the carbamates.
Organochlorine Insecticides were commonly used in the past, but
many have been removed from the market due to their health and environmental
effects and their persistence (e.g. DDT and chlordane).
Pyrethroid Pesticides were developed as a synthetic
version of the naturally occurring pesticide pyrethrin, which is found in
chrysanthemums. They have been modified to increase their stability in the
environment. Some synthetic pyrethroids are toxic to the nervous system.
Biopesticides
Biopesticides are certain types of pesticides derived
from such natural materials as animals, plants, bacteria, and certain
minerals. For example, canola oil and baking soda have pesticidal
applications and are considered biopesticides. At the end of 2001, there
were approximately 195 registered biopesticide active ingredients and 780
products. Biopesticides fall into three major classes:
(1) Microbial pesticides consist of a microorganism
(e.g., a bacterium, fungus, virus or protozoan) as the active ingredient.
Microbial pesticides can control many different kinds of pests, although
each separate active ingredient is relatively specific for its target
pest[s]. For example, there are fungi that control certain weeds, and
other fungi that kill specific insects.
The most widely used microbial pesticides are subspecies and strains of
Bacillus thuringiensis, or Bt. Each strain of this bacterium produces a
different mix of proteins, and specifically kills one or a few related
species of insect larvae. While some Bt's control moth larvae found on
plants, other Bt's are specific for larvae of flies and mosquitoes. The
target insect species are determined by whether the particular Bt produces
a protein that can bind to a larval gut receptor, thereby causing the
insect larvae to starve
(2) Plant-Incorporated-Protectants (PIPs) are
pesticidal substances that plants produce from genetic material that has
been added to the plant. For example, scientists can take the gene for the
Bt pesticidal protein, and introduce the gene into the plant's own genetic
material. Then the plant, instead of the Bt bacterium, manufactures the
substance that destroys the pest. The protein and its genetic material,
but not the plant itself, are regulated by EPA.
(3) Biochemical pesticides are naturally occurring
substances that control pests by non-toxic mechanisms. Conventional
pesticides, by contrast, are generally synthetic materials that directly
kill or inactivate the pest. Biochemical pesticides include substances,
such as insect sex pheromones, that interfere with mating, as well as
various scented plant extracts that attract insect pests to traps. Because
it is sometimes difficult to determine whether a substance meets the
criteria for classification as a biochemical pesticide, EPA has
established a special committee to make such decisions.
