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AGROCHEMICALS

Agrichemical refers to biocides (pesticides including insecticides, herbicides,


fungicides and nematicides) and synthetic fertilizers.
CLASSIFICATION OF PESTICIDES
Pesticides are chemical compounds useful in killing pests. Generally, a pesticide is
a chemical compound or even a biological agent such as a bacteria, virus,
antimicrobial, or disinfectant that prevents, incapacitates, or kills pests. The term
pesticide includes all of the following: herbicide, insecticide (which can involve
insect growth regulators, termiticides, etc.) nematicide, molluscicide, pesticide,
avicide, rodenticide, bactericide, insect repellent, animal repellent, antimicrobial
and fungicide.
The most popular of these are herbicides, which account for nearly 80% of all
pesticide use. Many pesticides serve as plant protection products (also known as
crop protection products) that usually protects plants from weeds, fungi or insects.
As an example-The fungus, Alternaria is used to battle Aquatic Weed, Salvinia.

A Brief History
Even before 2000 BC, humans have used pesticides to protect their crops. The
first known pesticide was the elemental sulphur dust used by ancient Sumerians
around 4,500 years ago in ancient Mesopotamia. Rigveda, about 4,000 years old,
refers to the use of poisonous plants to control pests. By the time of the
15th century, toxic chemicals such as arsenic, mercury and lead were useful in
destroying the pests in crops. Nicotine sulphate was derived from tobacco leaves
in the 17th century for use as an insecticide. The 19th century saw the introduction
of two more natural pesticides, pyrethrum, derived from chrysanthemums, and
rotenone, derived from the roots of tropical vegetables. Until the 1950s, pesticides
based on arsenic were dominant.
Paul Müller found that DDT was a highly effective insecticide. Until 1975
organochlorines such as DDT were dominant, but by the year of 1975
organophosphates and carbamate replaced DDT in the US. However, 20 years
later, because of the biological consequences and human safety concerns, almost
86 counties declared the banning of DDT. Since then, pyrethrin compounds have
become the dominant insecticide in the industry. Herbicides became popular in the
early 1960s, then came “triazine and other similar nitrogen-based compounds,
carboxylic acids including glyphosate and 2,4-dichlorophenoxyacetic acid”.

Definitions of Pesticides
The Food and Agriculture Organization (FAO) has defined pesticide as:
“any substance or mixture of substances intended for preventing, destroying or
controlling any pest, including vectors of human or animal disease, unwanted
species of plants or animals, causing harm during or otherwise interfering with the
production, processing, storage, transport, or marketing of food, agricultural
commodities, wood and wood products or animal feedstuffs, or substances that
may be administered to animals for the control of insects, arachnids, or other pests
in or on their bodies”.

Types of Pesticides
Pesticides are also referred to by the type of pest they control. Pesticides can be
either biodegradable pesticides, that break down into harmless compounds by
bacteria and other living organisms, or persistent/Non-Biodegradable pesticides,
which can take months or years to break down.

Classification of pesticides are according to the types of pests they


kill
Grouped by the pest types they Kill;

 Insecticides – Insects
 Herbicide – Plants
 Rodenticides – Rodents (rats & mice)
 Bactericides – Bacteria
 Fungicides – Fungicide
 Larvicides – Larvae

Depending on how biodegradable they are


Biodegradable Pesticides
Biodegradable pesticides are those that can be broken down into
harmless compounds by microbes and other living organisms within
less period of time.
Non-Biodegradable Pesticides
Few pesticides are known as non-biodegradable, also called persistent pesticides.
The most long-lived pesticide materials include aldrin, parathion, DDT,
chlordane, and endrin, they take a long period of time to break down. These
pesticides can survive in the soil for over 15 years or more.
Another way of thinking about pesticides is considering the chemical pesticides
extracted from a common source or some production method.
Chemical pesticides
Organophosphates
Many organophosphates are insecticides that impact on the nervous system by
compromising the enzyme that regulates the neurotransmitter.
Carbamate
Carbamate pesticides affect the nervous system by compromising the enzyme that
regulates the neurotransmitter similar to the organophosphates, but carbamate
enzyme effects are usually reversible.
Organochlorine Insecticides
This type was common in the early years when pesticides came into the market.
Many countries have banned organochlorine insecticides from their markets
because of their impacts and persistence on health and the environmental factors
(e.g., DDT, chlordane and toxaphene).
Pyrethroid
There are synthetic variants of pyrethrin, a naturally occurring pesticide present in
chrysanthemums (Flower). Their development is such a way they can maximize
their environmental resilience.
Sulfonylurea herbicides
The commercial production of sulfonylureas herbicides was for weed control like
flupyrsulfuron-methyl-sodium, ethoxysulfuron, chlorimuron-ethyl, bensulfuron-
methyl, azimsulfuron, and amidosulfuron, rimsulfuron, pyrazosulfuron-ethyl,
imazosulfuron, nicosulfuron, oxasulfuron, nicosulfuron, flazasulfuron,
primisulfuron-methyl, halosulfuron-methyl, pyrithiobac-sodium, cyclosulfamuron,
bispyribac-sodium, terbacil, sulfometuron-methyl Sulfosulfuron.
Biopesticides
The biopesticides are a type of pesticides obtained from natural resources such as
animals, plants, bacteria, and certain minerals.

Uses

 Pesticides are useful in controlling organisms that are toxic or harmful


to their environment.
 Herbicides are useful in controlling algae and weeds.
 They are useful in grocery stores and food storage facilities to control
rats and insects infesting on food.
 They are in use to kill mosquitoes that can spread life-threatening
diseases such as the West Nile virus, yellow fever, and malaria.
 Also, they are useful in the agricultural sector to prevent or kill insects
and other organisms that feed on crops.

FORMULATION OF PESTICIDES
A pesticide formulation is a mixture of chemicals which effectively controls
a pest. Formulating a pesticide involves processing it to improve its storage,
handling, safety, application, or effectiveness.1 See the text box on Some
Formulations.

What makes up a formulation?

 The pesticide formulation is a mixture of active and other ingredients


(previously called inert ingredients). An active ingredient is a substance
that prevents, kills, or repels a pest or acts as a plant regulator, desiccant,
defoliant, synergist, or nitrogen stabilizer.4 Pesticides come in many
different formulations due to variations in the active ingredient's
solubility, ability to control the pest, and ease of handling and transport.
 Synergists are a type of active ingredient that are sometimes added to
formulations.4 They enhance another active ingredient's ability to kill the
pest while using the minimum amount of active ingredient, but do not
themselves possess pesticidal properties. For example, insecticides
containing the active ingredient pyrethrins often contain piperonyl
butoxide or n-octyl bicycloheptane dicarboximide as a synergist.
 Other (or inert) ingredients may aid in the application of the active
ingredient. Other ingredients can be solvents, carriers, adjuvants, or any
other compound, besides the active ingredient, which is intentionally
added.4 There are many types of other ingredients: solvents are liquids
that dissolve the active ingredient, carriers are liquids or solid chemicals
that are added to a pesticide product to aid in the delivery of the active
ingredient, and adjuvants often help make the pesticide stick to or spread
out on the application surface (i.e., leaves).5 Other adjuvants aid in the
mixing of some formulations when they are diluted for application.

What do manufacturers consider when creating a formulation?

 The type of surface, training, equipment, runoff, drift, habits of the pest,
and safety are all considered when a manufacturer designs a pesticide
formulation.

Type of surface
 Some formulations are more effective on certain surfaces than others.
Discoloration or pitting of the surface of plants or other surfaces may
occur with some formulations.

Training and equipment

 Many pesticide products that the public purchases and uses are ready-to-use
(RTU) formulations which require no dilution and can be applied quickly and
conveniently. Examples of ready-to-use formulations used by homeowners
are granules for insect and weed control and baits for rodent control.
 Many of the formulations used by farmers and commercial applicators (like
pest control companies) need to be applied with certain equipment. These
formulations may also require certification or training for individuals
performing the application. For example, termiticide applicators may be
required by the Department of Agriculture in each state to complete specific
training in the use of termiticides.
 Some liquid pesticide formulations commonly used by farmers and
commercial applicators are applied with a compressed air sprayer, fogger, or
soil injector.6 Other liquid pesticide formulations used by farmers may require
the use of aircraft, low pressure boom sprayer, high-pressure sprayer, or ultra-
low-volume sprayer.6
 The equipment required for the application is listed on the label.

Runoff or drift

 Rain soon after the application may cause the pesticide to run off and
contaminate lakes, rivers, streams, or ponds.7
 Wind may carry or drift the pesticide during the application onto adjacent
property, bodies of water, people, or animals.
 Specific environmental precautionary statements may be present on the label
describing how to avoid runoff or drift.

Safety to people, animals, and the environment

 Individuals who apply, handle, transport, or dispose of pesticides should know


the proper manner in which to deal with them. Safety gear is important to
minimize potential exposure to pesticides during an application. An
applicator's proper personal protective equipment (PPE) may include a long
sleeve shirt, pants, closed-toe shoes, chemically resistant rubber gloves, a
respirator, and/or eye protection. The equipment required for an application
will be listed on the label.
 In addition to the safety of those working with pesticides, the safety of people,
pets, and the environment near the site of application need to be taken into
account.7 To facilitate this, the label often has precautionary statements to
protect wildlife and other non-target species.

Habits of the pest


 The pest needs to be identified. Information on how the pest feeds, its
reproductive habits, and its life cycle will help the manufacturer determine
which formulation would be the most effective.7

Can pesticides be mixed together?

 The pesticide product label will list any chemicals that it should not be mixed
with (i.e., incompatible with) or containers that it should not be mixed in. 4 For
example, wettable sulfur should not be mixed with Lorsban or Morestan
because they are incompatible.6
 Some pesticides can be mixed together (i.e., they are compatible with each
other).
 Not all pesticides can be mixed together (incompatible) because they
separate out of the solution, gel, curdle, or clog the equipment during
application.
 Pesticides that are physically different (i.e., dust versus liquid) are typically
incompatible.

How are incompatibilities avoided?

 Verify with the pesticide label what types of pesticide formulations to avoid
mixing. Formulated pesticide products that are ready-to-use (RTU) liquids and
concentrated liquids that have been diluted according to label instructions
can be mixed together. However, undiluted liquid concentrations should not
be combined.
 To reduce incompatibilities of flowable, wettable powder, and water-
dispersible granule formulations, regular shaking is needed.2
 If you have questions about compatibility or other pesticide-related issues
contact your State Department of Agriculture or your local County Cooperative
Extension Service for more information.
TOXICITY OF PESTICIDES

Pesticides are designed to control pests, but they can also be toxic (poisonous)
to desirable plants and animals, including humans. Some pesticides are so
highly toxic that very small quantities can kill a person, and almost any
pesticide can make people ill if they are exposed to a sufficient amount.
Because even fairly safe pesticides can irritate the skin, eyes, nose, or mouth, it
is a good idea to understand how pesticides can be toxic so you can follow
practices designed to reduce or eliminate your exposure and the exposure of
others to them.
HOW PESTICIDES ENTER THE BODY

Before a pesticide can harm you, it must be taken into the body. Pesticides can
enter the body orally (through the mouth and digestive system); dermally
(through the skin); or by inhalation (through the nose and respiratory system).
ORAL EXPOSURE

Oral exposure may occur because of an accident, but is more likely to occur as
the result of carelessness, such as blowing out a plugged nozzle with your
mouth, smoking or eating without washing your hands after using a pesticide,
splashing concentrate while mixing, or eating fruit that has been recently
sprayed with a pesticide containing residues above the tolerance set for the
commodity by the Environmental Protection Agency. The seriousness of the
exposure depends upon the oral toxicity of the material and the amount
swallowed.
DERMAL EXPOSURE

Dermal (skin) exposure accounts for about 90% of the exposure pesticide users
receive from nonfumigant pesticides. It may occur any time a pesticide is
mixed, applied, or handled, and it often goes undetected. Both liquid pesticides
and dry materials—dusts, wettable powders, and granules—can be absorbed
through the skin.

The seriousness of dermal exposure depends upon:


 the dermal toxicity of the pesticide;
 rate of absorption through the skin;
 the size of the skin area contaminated;
 the length of time the material is in contact with the skin; and
 the amount of pesticide on the skin.

Absorption continues to take place on all of the affected skin area as long as the
pesticide is in contact with the skin. The seriousness of the exposure is
increased if the contaminated area is large or if the material remains on the skin
for a period of time.

Rates of absorption through the skin are different for different parts of the body.
Usually, absorption through the forearm is the standard against which
absorption rates in other areas of the body are tested. Absorption is over 11
times faster in the lower groin area than on the forearm (Table 1). Absorption
through the skin in the genital area is rapid enough to approximate the effect of
injecting the pesticide directly into the bloodstream.

INHALATION EXPOSURE

Inhalation exposure results from breathing pesticide vapors, dust, or spray


particles. Like oral and dermal exposure, inhalation exposure is more serious
with some pesticides than with others, particularly fumigant pesticides, which
form gases.

Inhalation exposure can occur by breathing smoke from burning containers;


breathing fumes from pesticides while applying them without protective
equipment; and inhaling fumes while mixing and pouring pesticides. Some
pesticides will have statements on their labels requiring the use of a specified
respirator. Another means of inhalation exposure is smoking tobacco products
containing pesticide residues.
TOXICITY

Toxicity refers to the ability of a substance to produce adverse effects. These


adverse effects may range from slight symptoms such as headaches to severe
symptoms like coma, convulsions, or death. Poisons work by altering normal
body functions. Most toxic effects are naturally reversible and do not cause
permanent damage if prompt medical treatment is sought. Some poisons,
however, cause irreversible (permanent) damage.

Toxicity is usually divided into two types, acute or chronic, based on the
number of exposures to a poison and the time it takes for toxic symptoms to
develop. Acute toxicity is due to short-term exposure and happens within a
relatively short period of time, whereas chronic exposure is due to repeated or
long-term exposure and happens over a longer period. (Table 2).

HOW TOXICITY IS MEASURED

All new pesticides are tested to establish the type of toxicity and the dose
necessary to produce a measurable toxic reaction. In order to compare the
results of toxicity tests done in different labs, there are strict testing procedures.
Toxicity testing is extensive (involving many phases) and therefore expensive.
Humans, obviously, cannot be used as test subjects, so toxicity testing is done
with animals and plants. Since different species of animals respond differently
to chemicals, a new chemical is generally tested in mice, rats, rabbits, and dogs.
The results of these toxicity tests are used to predict the safety of the new
chemical to humans.

Toxicity tests are based on two premises. The first premise is that information
about toxicity in animals can be used to predict toxicity in humans. Years of
experience have shown that toxicity data obtained from a number of animal
species can be useful in predicting human toxicity, while data obtained from a
single species may be inaccurate. The second premise is that by exposing
animals to large doses of a chemical for short periods of time, we can predict
human toxicity from exposure to small doses for long periods of time. Both
premises have been questioned.

Chronic toxicity is tested using animal feeding studies. In these studies, the
pesticide under investigation is incorporated into the daily diet and fed to
animals from a very young to a very old age. These, as well as the reproductive
effects studies, are designed to arrive at a No-Observable-Effect-Level (NOEL);
that is, a level in the total diet that causes no adverse effect in treated animals
when compared to untreated animals maintained under identical conditions.
This NOEL is expressed on a mg/kg of body weight/day basis.
A Reference Dose (RfD), also known as Acceptable Daily Intake (ADI), is
usually established at 1/100 of the NOEL, in order to add an additional margin
of safety. The RfD (ADI) is the amount of chemical that can be consumed daily
for a lifetime without ill effects.
ACUTE TOXICITY

The acute toxicity of a chemical refers to its ability to do systemic damage as a


result of a one-time exposure to relatively large amounts of the chemical. A
pesticide with a high acute toxicity may be deadly if even a very small amount
is absorbed. The signal words on the label (Table 3) are based on the acute
toxicity of the pesticide. Acute toxicity may be measured as acute oral (through
the mouth), acute dermal (through the skin) and acute inhalation (through the
lungs or respiratory system).

Acute Toxicity Measures

The commonly used term to describe acute toxicity is LD50. LD means lethal
dose (deadly amount) and the subscript 50 means that the dose was acutely
lethal to 50% of the animals to whom the chemical was administered under
controlled laboratory conditions. The test animals are given specific amounts of
the chemical in either one oral dose or by a single injection, and are then
observed for a specified time.

The lower the LD50 value, the more acutely toxic the pesticide. Therefore, a
pesticide with an oral LD50 of 500 mg/kg would be much less toxic than a
pesticide with an LD50 of 5 mg/kg. LD50 values are expressed as milligrams per
kilogram (mg/kg), which means milligrams of chemical per kilogram of body
weight of the animal. Milligram (mg) and kilogram (kg) are metric units of
weight. Milligrams per kilogram is the same measure as parts per million. To
put these units into perspective, 1 ppm is analogous to 1 inch in 16 miles or 1
minute in 2 years.

For example, if the oral LD50 of the insecticide parathion is 4 mg/kg, a dose of 4
parts of parathion for every million parts of body weight would be lethal to at
least half of the test animals.

LD50 values are generally expressed on the basis of active ingredient. If a


commercial product is formulated to contain 50 percent active ingredient, it
would take two parts of the material to make one part of the active ingredient. In
some cases, other chemicals mixed with the active ingredient for formulating
the pesticide product may cause the toxicity to differ from that of the active
ingredient alone.
Acute inhalation toxicity is measured by LC50. LC means lethal concentration.
Concentration is used instead of dose because the amount of pesticide inhaled in
the air is being measured. LC50 values are measured in milligrams per liter.
Liters are metric units of volume similar to a quart. The lower the LC50 value,
the more poisonous the pesticide.
CHRONIC TOXICITY

Chronic toxicity refers to harmful effects produced by long-term exposure to


pesticides. Less is known about the chronic toxicity of pesticides than is known
about their acute toxicity, not because it is of less importance, but because
chronic toxicity is gradual rather than immediate and is revealed in much more
complex and subtle ways. While situations resulting in acute exposure (a single
large exposure) do occur, they are nearly always the result of an accident or
careless handling. On the other hand, people may be routinely exposed to
pesticides while mixing, loading, and applying pesticides or by working in
fields after pesticides have been applied.
Chronic Toxicity Measures

There is no standard measure like the LD50 for chronic toxicity. How chronic
toxicity of chemicals is studied depends upon the adverse effect being studied.
Chronic adverse effects may include carcinogenic effects (cancers), teratogenic
effects (birth defects), mutagenic effects (genetic mutations), hemotoxic effects
(blood disorders), endocrine disruption (hormonal problems), and reproductive
toxicity (infertility or sterility).
CARCINOGENESIS (ONCOGENESIS)

Carcinogenesis means the production of malignant tumors. Oncogenesis is a


generic term meaning the production of tumors which may or may not be
carcinogenic. The terms tumor, cancer, or neoplasm are all used to mean an
uncontrolled progressive growth of cells. In medical terminology, a cancer is
considered a malignant (potentially lethal) neoplasm. Carcinogenic or
oncogenic substances are substances that can cause the production of tumors.
Examples are asbestos and cigarette smoke.
TERATOGENESIS

Teratogenesis is the production of birth defects. A teratogen is anything that is


capable of producing changes in the structure or function of an embryo or fetus
exposed before birth. An example of a chemical teratogen is the drug
thalidomide, which caused birth defects in children when their mothers used it
during their pregnancies. Measles virus infection during pregnancy has
teratogenic effects.
MUTAGENESIS
Mutagenesis is the production of changes in genetic structure. A mutagen is a
substance that causes a genetic change. Many mutagenic substances are
oncogenic, meaning they also produce tumors. Many oncogenic substances are
also mutagens.
REPRODUCTIVE TOXICITY

Some chemicals have effects on the fertility or reproductive rates of animals.


Males or females can be affected.
LABEL IDENTIFICATION OF ACUTE AND CHRONIC
TOXICITY

To alert pesticide users to the acute toxicity of a pesticide, a signal word may
appear on the label. Four different categories are used (Table 3). Signal words
are used to tell the user whether the chemical is highly toxic, moderately toxic,
slightly toxic, or relatively non-toxic. These label warnings are based, for the
most part, on the chemical's acute toxicity. For example, the acute oral and
acute dermal toxicity of a pesticide may be in the slightly toxic category. But if
the acute inhalation toxicity is in the highly toxic category, the pesticide label
will have the signal words for a highly toxic pesticide. The degree of eye or skin
irritation caused by the pesticide also influences the signal word.

For chronic toxicity there is no comparable set of signal words like those used
for acute toxicity. Instead, a statement identifying the specific chronic toxicity
problem is sometimes used on the label. Such a statement might read "This
product contains (name of chemical), which has been determined to cause
tumors or birth defects in laboratory animals." Chronic toxicity warning
statements may be accompanied by label directions to wear certain kinds of
protective clothing when handling or working with the pesticide to minimize or
eliminate exposure to the pesticide.

It is important to read the label to look for signal words identifying the product's
acute toxicity and for statements identifying any chronic toxicity problem. A
pesticide may be low in acute toxicity (signal word caution), but it may have a
label statement identifying potential chronic toxicity.
SAFETY FACTORS

Extensive residue trials are conducted on crops to determine levels of the


pesticide that remain in or on growing crops after treatment with the pesticide.
These trials lead to the establishment of a tolerance for residues of the chemical
on food commodities. A tolerance is the maximum allowable amount of the
pesticide permitted in or on a specific food commodity at harvest. The
directions for use found on the product label are written to assure that residues
in food commodities are below the tolerance. The tolerance is set low enough to
assure that even if someone ate only food items with residues of a given
pesticide at the tolerance limit, there would still be a safety factor of at least 100
when compared to a level causing no observable effects in laboratory animals.
This is, of course, a worst-case situation, since all crops on which the pesticide
is registered for use would not be treated with the chemical, and in most cases
residue levels would be well below the tolerance because pre-harvest intervals
are almost invariably longer than the minimum period stated on the label.
Further reduction of residues may occur in storage or from washing, trimming,
and processing.
DOSE-RESPONSE

Dose-response is the measure of the amount of a given substance an organism


must absorb to produce an effect. The extensive amount of data developed
about a given pesticide is often used against it because this key piece of
information is ignored. For example, some acute toxicity studies, which are
designed to include dosage levels high enough to produce deaths, are cited as
proof of the chemical's dangers. Chronic effects seen at very high doses in
lifetime feeding studies are misinterpreted and considered as proof that no
exposure to the chemical should be allowed.

Major improvements in analytical chemistry permit detection of the presence of


chemicals at extremely low levels of parts per billion (ppb) and even sometimes
parts per trillion (ppt). A certain chemical may have been found in a food or
beverage, and the amount found is expressed in parts per million or parts per
billion. Often, no information is provided to assist consumers in comprehending
the meaning of these numbers. Frequently, this information neglects the issue of
dose-response, the key principle of toxicology, which, simply stated, is "the
dose makes the poison." The concentration of a chemical in any substance is
meaningless unless it is related to the toxicity of the chemical and the potential
for exposure and absorption. Chemicals of low toxicity such as table salt or
ethyl alcohol can be fatal if consumed in large amounts. Conversely a highly
toxic material may pose no hazard when exposure is minimal.
MONITORING FOR RESIDUES

Monitoring foods for pesticide residues is carried out by the Food and Drug
Administration (FDA) and the United States Department of Agriculture
(USDA). Crops found to contain residues over the official tolerance (maximum
legal level) established by the EPA must be destroyed. The threat of crop
destruction with resultant financial loss is a strong incentive for farmers to
observe use instructions on pesticide labels and thus assures that residues will
be below established tolerances. Crops grown for export are often checked for
residues by foreign residue laboratories to assure that local tolerance limits are
not exceeded. Lastly, market-basket surveys (analyses of food items from
grocery stores) have confirmed the low exposure of the general public to
pesticides in foods.
HAZARD

Hazard is a function of the toxicity of a pesticide and the potential for exposure
to it. We do not have control of the toxicity of a pesticide because toxicity is a
given characteristic of a particular pesticide; however, we can have control over
our exposure to pesticides. We achieve control over exposure by following
several safety practices including the use of protective clothing and equipment
(PPE).

All pesticides are hazardous if misused, no matter what their toxicity. All
pesticides can be handled safely by using safety practices that minimize or
eliminate exposure to them.

Federal laws regulating pesticides have placed the burden of proving safety of
pesticide usage on the manufacturer. Hazard evaluation studies are generally
done by scientific laboratories maintained by the manufacturer or through
outside contract laboratories. Few products are subjected to the extensive and
vigorous testing pesticides undergo before they are marketed. In fact, many
promising pesticide products are not marketed because they do not pass the
extensive toxicology testing. Older pesticide products that were registered
before the current toxicology testing standards were established are being re-
evaluated to ensure they meet current standards. Precautions and other safety
information found on the product's label are based on information from these
tests. By reading and following the directions on the label, users can minimize
or eliminate hazards due to use of the pesticide to themselves and others.
COMMON PESTICIDE POISONINGS

The pesticides most often implicated in poisonings, injuries, and illnesses,


according to 2010 data from the American Association of Poison Control
Center's Toxic Exposure Surveillance System, are listed in Table 4.

Cases listed as organophosphates (and the other categories as well) may also
include other insecticides such as carbamates and organochlorine in a single
product. Asymptomatic cases are included in Table 4 only.

This list cannot be considered representative of all symptomatic poisonings


because it only shows cases reported to Poison Control Centers. However, it
does give a sense of the relative frequency and risk of poisoning from various
agents or classes of agents. The relative frequency of cases generally reflects
how widely a product is used in the environment. For example, a number of
disinfectants occur in the top ten partly because they are far more commonly
found in the home and work environment than other pesticides. Denominator
information on the population at risk (numbers exposed) would be needed to
better understand the relative risk of different pesticides. However, the main
purpose is to give physicians a sense of what types of cases they are most likely
to see in their practice.

FUTURE TRENDS OF PEST CONTROL


Pest control has been a critical aspect of maintaining a healthy environment and
protecting crops, homes, and businesses.
The pest control industry has seen significant developments and advancements over
the years.
From the introduction of pesticides to the integration of smart technology, pest control
companies have made progress in mitigating the negative effects of pests.
As we move into the future, several predictions and innovations are expected to shape
the future of pest control.
In this article, we will discuss some of these predictions and innovations.
Contents:
1. Increased use of Integrated Pest Management (IPM) approach
2. Development of new pesticides
3. Increased use of smart technology
4. Use of drones in pest control
5. Use of pheromone traps
6. Conclusion
1. Increased use of Integrated Pest Management (IPM) approach
Integrated Pest Management (IPM) is a holistic approach to pest control that
combines different pest management techniques to prevent and control pest
infestations. IPM focuses on preventing pests from accessing food, water, and
shelter, which are essential for their survival. By eliminating these resources, the pests
will not survive and will, therefore, be eliminated.
IPM involves identifying the pest species, understanding their biology and behavior,
and using the most effective and least toxic methods to manage them. These
methods may include biological control, cultural control, physical control, and
chemical control. IPM is considered a sustainable approach to pest control since it
minimizes the use of pesticides, which can be harmful to the environment and human
health.
As consumers become more environmentally conscious, there is a growing demand
for sustainable pest control methods. The use of IPM is expected to increase in the
future as pest control companies focus on providing sustainable solutions to their
clients.
2. Development of new pesticides
Pesticides have been a critical tool in pest control for many years. However, the
overuse of pesticides has led to the development of resistance in some pest species.
This has led to the need for the development of new pesticides that are more effective
and target specific pest species.
In recent years, there has been an increased focus on developing biopesticides, which
are derived from natural sources such as plants, bacteria, and fungi. Biopesticides are
considered safe and environmentally friendly since they have minimal impact on non-
target organisms and the environment.
Additionally, the development of new pesticides is expected to focus on reducing the
toxicity of existing pesticides, making them safer for use. The use of nanotechnology
in pesticide development is also being explored to improve the effectiveness and
efficiency of pesticides.
3. Increased use of smart technology
Smart technology is transforming many industries, including pest control. Smart
technology involves the integration of sensors, cameras, and other devices to monitor
and control pests. Smart technology can be used in both residential and commercial
settings to detect and prevent pest infestations.
One example of smart technology in pest control is the use of bait stations that are
equipped with sensors. These sensors can detect when the bait has been consumed
and alert the pest control company, allowing them to take appropriate action.
Smart technology can also be used to monitor the conditions that attract pests, such
as temperature and humidity. This information can be used to predict and prevent pest
infestations before they occur.
4. Use of drones in pest control
Drones are becoming increasingly popular in various industries, including pest control.
Drones can be used to monitor and inspect large areas quickly and efficiently, making
them ideal for pest control in agriculture and other outdoor settings.
Drones equipped with cameras and sensors can detect pest infestations, allowing
pest control companies to take appropriate action. Drones can also be used to spray
pesticides over large areas, reducing the time and cost of pest control operations.
5. Use of pheromone traps
Pheromone traps are becoming increasingly popular in pest control, particularly in
agriculture. Pheromones are chemicals that insects produce to communicate with
each other. Pheromone traps use synthetic versions of these chemicals to lure insects
to a trap, where they are captured.
In conclusion, the future of pest control is likely to be shaped by advancements in technology
and sustainability. Predictions suggest that artificial intelligence, drones, and precision
agriculture will play a significant role in identifying and managing pest populations in the
coming years. In addition, there will be a greater emphasis on eco-friendly pest control
methods and the use of natural predators as an alternative to chemical treatments.
With the ever-increasing demand for sustainable solutions, pest control companies
must adapt and innovate to meet these evolving needs.
The future of pest control looks promising, with a focus on reducing the environmental
impact of pest management while ensuring effective results.

CONTROL OF WEEDS
Weed control is important in agriculture. Methods include hand cultivation
with hoes, powered cultivation with cultivators, smothering with mulch,
lethal wilting with high heat, burning, and chemical control with
herbicides (weed killers).
Weed control is a type of pest control, which attempts to stop or reduce growth
of weeds, especially noxious weeds, with the aim of reducing their competition
with desired flora and fauna including domesticated plants and livestock, and in
natural settings preventing non native species competing with native species.
Weed control is important in agriculture. Methods include hand cultivation
with hoes, powered cultivation with cultivators, smothering with mulch,
lethal wilting with high heat, burning, and chemical
control with herbicides (weed killers).
Need for control
Weeds compete with productive crops or pasture, they can be poisonous,
distasteful, produce burrs, thorns or otherwise interfere with the use and
management of desirable plants by contaminating harvests or interfering with
livestock.
Weeds compete with crops for space, nutrients, water and light. Smaller, slower
growing seedlings are more susceptible than those that are larger and more
vigorous. Onions are one of the most vulnerable, because they are slow to
germinate and produce slender, upright stems. .By contrast broad beans produce
large seedlings and suffer far fewer effects other than during periods of water
shortage at the crucial time when the pods are filling out. Transplanted crops
raised in sterile soil or potting compost gain a head start over germinating
weeds.
Weeds also vary in their competitive abilities according to conditions and
season. Tall-growing vigorous weeds such as fat hen (Chenopodium album) can
have the most pronounced effects on adjacent crops, although seedlings of fat
hen that appear in late summer produce only small plants. Chickweed (Stellaria
media), a low growing plant, can happily co-exist with a tall crop during the
summer, but plants that have overwintered will grow rapidly in early spring and
may swamp crops such as onions or spring greens.
The presence of weeds does not necessarily mean that they are damaging a crop,
especially during the early growth stages when both weeds and crops can grow
without interference. However, as growth proceeds they each begin to require
greater amounts of water and nutrients. Estimates suggest that weed and crop
can co-exist harmoniously for around three weeks before competition becomes
significant. One study found that after competition had started, the final yield of
onion bulbs was reduced at almost 4% per day.
Perennial weeds with bulbils, such as lesser celandine and oxalis, or with
persistent underground stems such as couch grass (Agropyron repens)
or creeping buttercup (Ranunculus repens) store reserves of food, and are thus
able to persist in drought or through winter. Some perennials such as couch
grass exude allelopathic chemicals that inhibit the growth of other nearby
plants.
Weeds can also host pests and diseases that can spread to cultivated
crops. Charlock and Shepherd's purse may carry clubroot, eelworm can be
harboured by chickweed, fat hen and shepherd's purse, while the cucumber
mosaic virus, which can devastate the cucurbit family, is carried by a range of
different weeds including chickweed and groundsel.
Pests such as cutworms may first attack weeds but then move on to cultivated
crops.
Some plants are considered weeds by some farmers and crops by
others. Charlock, a common weed in the southeastern US, are weeds according
to row crop growers, but are valued by beekeepers, who seek out places where it
blooms all winter, thus providing pollen for honeybees and other pollinators. Its
bloom resists all but a very hard freeze, and recovers once the freeze ends.
Weed propagation
Seeds
Annual and biennial weeds such as chickweed, annual meadow
grass, shepherd's purse, groundsel, fat hen, cleaver, speedwell and hairy
bittercress propagate themselves by seeding. Many produce huge numbers of
seed several times a season, some all year round. Groundsel can produce 1000
seed, and can continue right through a mild winter, whilst Scentless
Mayweed produces over 30,000 seeds per plant. Not all of these
will germinate at once, but over several seasons, lying dormant in the soil
sometimes for years until exposed to light. Poppy seed can survive 80–100
years, dock 50 or more. There can be many thousands of seeds in a square foot
or square metre of ground, thus any soil disturbance will produce a flush of
fresh weed seedlings.
Subsurface/surface
The most persistent perennials spread by underground creeping rhizomes that
can regrow from a tiny fragment. These include couch grass, bindweed, ground
elder, nettles, rosebay willow herb, Japanese knotweed, horsetail and bracken,
as well as creeping thistle, whose tap roots can put out lateral roots. Other
perennials put out runners that spread along the soil surface. As they creep they
set down roots, enabling them to colonise bare ground with great rapidity. These
include creeping buttercup and ground ivy. Yet another group of perennials
propagate by stolons- stems that arch back into the ground to reroot. The most
familiar of these is the bramble.
Methods
Weed control plans typically consist of many methods which are divided into
biological, chemical, cultural, and physical/mechanical control.
Physical/mechanical methods
Coverings
In a domestic gardens, methods of weed control include covering an area of
ground with a material that creates an unsuitable environment for weed growth,
known as a weed mat. For example, several layers of wet newspaper prevent
light from reaching plants beneath, which kills them.
In the case of black plastic, the greenhouse effect kills the plants. Although the
black plastic sheet is effective at preventing weeds that it covers, it is difficult to
achieve complete coverage. Eradicating persistent perennials may require the
sheets to be left in place for at least two seasons.
Some plants are said to produce root exudates that
suppress herbaceous weeds. Tagetes minuta is claimed to be effective against
couch and ground elder, whilst a border of comfrey is also said to act as a
barrier against the invasion of some weeds including couch. A 5–10 centimetres
(2.0–3.9 in) layer of wood chip mulch prevents some weeds from sprouting.
Gravel can serve as an inorganic mulch.
Irrigation is sometimes used as a weed control measure such as in the case
of paddy fields to kill any plant other than the water-tolerant rice crop.
Manual removal

Many gardeners still remove weeds by manually pulling them out of the ground,
making sure to include the roots that would otherwise allow some to re-sprout.
Hoeing off weed leaves and stems as soon as they appear can eventually
weaken and kill perennials, although this will require persistence in the case of
plants such as bindweed. Nettle infestations can be tackled by cutting back at
least three times a year, repeated over a three-year period. Bramble can be dealt
with in a similar way.
A highly successful, mostly manual, removal programme of weed control in
natural bush land has been the control of sea spurge by Sea Spurge Remote
Area Teams in Tasmania.
Tillage
Weed control through tilling with hoes, circa
1930-40s
Ploughing includes tilling of soil, intercultural ploughing and summer
ploughing. Ploughing uproots weeds, causing them to die. Summer ploughing
also helps in killing pests.

A mechanical weed control device


Mechanical tilling with various types of cultivators can remove weeds around
crop plants at various points in the growing process.
An Aquamog can be used to remove weeds covering a body of water.
Thermal

Pesticide-free thermic weed control with a weed


burner on a potato field in Dithmarschen, Germany
Several thermal methods can control weeds.
Flame weeding uses a flame several centimetres/inches away from the weeds to
singe them, giving them a sudden and severe heating. The goal of flame
weeding is not necessarily burning the plant, but rather causing a
lethal wilting by denaturing proteins in the weed. Similarly, hot air weeders can
heat up the seeds to the point of destroying them. Flame weeders can be
combined with techniques such as stale seedbeds (preparing and watering the
seedbed early, then killing the nascent crop of weeds that springs up from it,
then sowing the crop seeds) and pre-emergence flaming (doing a flame pass
against weed seedlings after the sowing of the crop seeds but before those
seedlings emerge from the soil—a span of time that can be days or weeks).
Hot foam causes the cell walls to rupture, killing the plant. Weed burners heat
up soil quickly and destroy superficial parts of the plants. Weed seeds are often
heat resistant and even react with an increase of growth on dry heat.
Since the 19th century soil steam sterilization has been used to clean weeds
completely from soil. Several research results confirm the high effectiveness of
humid heat against weeds and its seeds.
Soil solarization in some circumstances is very effective at eliminating weeds
while maintaining grass. Planted grass tends to have a higher heat/humidity
tolerance than unwanted weeds.
Lasers
In precision agriculture, novel agricultural robots and machines can use
lasers for weed control, called "laserweeding".Their benefits may include
"healthier crops and soil, decreased herbicide use, and reduced chemical and
labor costs".
Seed targeting
In 1998, the Australian Herbicide Resistance Initiative debuted. gathered fifteen
scientists and technical staff members to conduct field surveys, collect seeds,
test for resistance and study the biochemical and genetic mechanisms of
resistance. A collaboration with DuPont led to a mandatory herbicide labelling
program, in which each mode of action is clearly identified by a letter of the
alphabet.
The key innovation of the Australian Herbicide Resistance Initiative has been to
focus on weed seeds. Ryegrass seeds last only a few years in soil, so if farmers
can prevent new seeds from arriving, the number of sprouts will shrink each
year. Until the new approach farmers were unintentionally helping the seeds.
Their combines loosen ryegrass seeds from their stalks and spread them over the
fields. In the mid-1980s, a few farmers hitched covered trailers, called "chaff
carts", behind their combines to catch the chaff and weed seeds. The collected
material is then burned.
An alternative is to concentrate the seeds into a half-meter-wide strip called
a windrow and burn the windrows after the harvest, destroying the seeds. Since
2003, windrow burning has been adopted by about 70% of farmers in Western
Australia.
Yet another approach is the Harrington Seed Destructor, which is an adaptation
of a coal pulverizing cage mill that uses steel bars whirling at up to 1500 rpm. It
keeps all the organic material in the field and does not involve combustion, but
kills 95% of seeds.
Cultural methods
Stale seed bed
Another manual technique is the ‘stale seed bed’, which involves cultivating the
soil, then leaving it fallow for a week or so. When the initial weeds sprout, the
grower lightly hoes them away before planting the desired crop. However, even
a freshly cleared bed is susceptible to airborne seed from elsewhere, as well as
seed carried by passing animals on their fur, or from imported manure.
Buried drip irrigation
Buried drip irrigation involves burying drip tape in the subsurface near the
planting bed, thereby limiting weeds access to water while also allowing crops
to obtain moisture. It is most effective during dry periods.
Crop rotation
Rotating crops with ones that kill weeds by choking them out, such
as hemp, Mucuna pruriens, and other crops, can be a very effective method of
weed control. It is a way to avoid the use of herbicides, and to gain the benefits
of crop rotation.
Biological methods
A biological weed control regiment can consist of biological control
agents, bioherbicides, use of grazing animals, and protection of natural
predators. Post-dispersal, weed seed predators, like ground beetles and small
vertebrates, can substantially contribute to the weed regulation by removing
weed seeds from the soil surface and thus reduce seed bank size. Several studies
provided evidence for the role of invertebrates to the biological control of weeds
Animal grazing
Companies using goats to control and eradicate leafy spurge, knapweed, and
other toxic weeds have sprouted across the American West.
Chemical methods
Herbicides

A tractor spraying herbicide onto a field of crops


The above described methods of weed control use no or very limited chemical
inputs. They are preferred by organic gardeners or organic farmers.
However weed control can also be achieved by the use of herbicides. Selective
herbicides kill certain targets while leaving the desired crop relatively
unharmed. Some of these act by interfering with the growth of the weed and are
often based on plant hormones. Herbicides are generally classified as follows;
Contact herbicides destroy only plant tissue that contacts the herbicide.
Generally, these are the fastest-acting herbicides. They are ineffective on
perennial plants that can re-grow from roots or tubers.

 Systemic herbicides are foliar-applied and move through the plant


where they destroy a greater amount of tissue. Glyphosate is currently
the most used systemic herbicide.
 Soil-borne herbicides are applied to the soil and are taken up by the
roots of the target plant.
 Pre-emergent herbicides are applied to the soil and prevent
germination or early growth of weed seeds.
In agriculture large scale and systematic procedures are usually required, often
by machines, such as large liquid herbicide 'floater' sprayers, or aerial
application.
These are thought to likely have several substantial detrimental impacts (e.g. on
soils, health and insects) – which may partly explain the development of
alternatives described here – and there are also systematic procedures using
herbicides that have lower impacts such as robots and machines that apply low
amounts with high precision.
Organic approaches
Organic weed control involves anything other than applying manufactured
chemicals. Typically a combination of methods are used to achieve satisfactory
control.
Sulfur in some circumstances is accepted within British Soil
Association standards.
Bradley method
The Bradley Method of Bush Regeneration uses ecological processes to do
much of the work.
Perennial weeds also propagate by seeding; the airborne seed of
the dandelion and the rose-bay willow herb parachute far and wide. Dandelion
and dock also put down deep tap roots, which, although they do not spread
underground, are able to regrow from any remaining piece left in the ground.
Hybrid
One method of maintaining the effectiveness of individual strategies is to
combine them with others that work in complete different ways. Thus seed
targeting has been combined with herbicides. In Australia seed management has
been effectively combined with trifluralin and clethodim.
Herbicide resistance
Resistance occurs when a target plant species does not respond to a chemical
that previously used to control it. It has been argued that over-reliance on
herbicides along with the absence of any preventive or other cultural practices
resulted in the evolution and spread of herbicide-resistant weeds. Increasing
number of herbicide resistance weeds around the world has led to warnings on
reducing frequent use of herbicides with the same or similar modes of action
and combining chemicals with other weed control methods; this is called
'Integrated Weed Management'.
Farming practices
Herbicide resistance recently became a critical problem as many Australian
sheep farmers switched to exclusively growing wheat in their pastures in the
1970s. In wheat fields, introduced varieties of ryegrass, while good for grazing
sheep, are intense competitors with wheat. Ryegrasses produce so many seeds
that, if left unchecked, they can completely choke a field. Herbicides provided
excellent control, while reducing soil disrupting because of less need to plough.
Within little more than a decade, ryegrass and other weeds began to develop
resistance. Australian farmers evolved again and began diversifying their
techniques.
In 1983, patches of ryegrass had become immune to Hoegrass, a family of
herbicides that inhibit an enzyme called acetyl coenzyme A carboxylase.
Ryegrass populations were large, and had substantial genetic diversity, because
farmers had planted many varieties. Ryegrass is cross-pollinated by wind, so
genes shuffle frequently. Farmers sprayed inexpensive Hoegrass year after year,
creating selection pressure, but were diluting the herbicide in order to save
money, increasing plants survival. Hoegrass was mostly replaced by a group of
herbicides that block acetolactate synthase, again helped by poor application
practices. Ryegrass evolved a kind of "cross-resistance" that allowed it to
rapidly break down a variety of herbicides. Australian farmers lost four classes
of herbicides in only a few years. As of 2013 only two herbicide classes,
called Photosystem II and long-chain fatty acid inhibitors, had become the last
hope.
Weed societies
Internationally, weed societies help collaboration in weed science and
management. In North America the Weed Science Society of America (WSSA)
was founded in 1956 and publishes three journals: Weed Science, Weed
Technology, and Invasive Plant Science and Management. In Britain, European
Weed Research Council was established in 1958 and later expanded their scope
under the name European Weed Research Society. The main journal of this
society is Weed Research. Moreover, the Council of Australasian Weed Society
(CAWS) serves as a centre for information on Australian weeds, while New
Zealand Plant Protection Society (NZPPS) facilitates information sharing in
New Zealand.
Strategic weed management is a process of managing weeds at a district,
regional or national scale. In Australia the first published weed management
strategies were developed in Tasmania, New South Wales and South Australian
1999, followed by the National Weeds Strategy in 1999.
HOUSEHOLD AGROCHEMICALS
Households use chemical pesticides, which include herbicides, insecticides and
fungicides, to kill pests and to help improve the look of lawns and gardens.
These products can contaminate the air, water, soil and food sources and have
negative effects on human and environmental health.
Pesticides used in and around the home to control pests including insects,
weeds, rodents, fungi, and germs. Many household products, such as bleach, are
pesticides. Liquid soap, furniture polish, and antifreeze are examples of
household chemicals which have hazards similar to pesticides; some are quite
dangerous, while others are much less harmful. Signal words such as danger,
warning, or caution, and precautionary statements (example: irritant to skin and
eyes, harmful if swallowed) on labels of all household chemicals indicate
product hazards and how to handle them safely.
HAZARDS ASSOCIATED WITH THE USE OF AGROCHEMICALS
AND ENVIRONMENTAL ASPECTS
Agrochemicals is the generic name given to chemicals such as fertilizers,
pesticides and insecticides. Agrochemicals, as the name suggests, are used in
agriculture to facilitate plant growth and protection. They are also called
agricultural chemicals.
These chemicals were initially used to improve crop production, however, their
overuse has now affected the environment. Agrochemicals seep into the
surrounding land and water bodies, entering the food chain which leads to
bioaccumulation. Regarding their impact on crops, excessive use of such
chemicals generates a significant amount of residues. These residues cause
nutrient imbalance and quality-reduction of agricultural produce. Consumption
of these residues has been linked to various illnesses. For example, pesticide
residues in food can increase the risk of asthma in humans.
Effect on Soil
 They may kill bacteria and other organisms beneficial to the soil
 Increase nitrate content in the soil
 Alter pH levels
 Unnatural growth effects
 Residual effects
 Can bioaccumulate; thereby entering the food chain

Effect on Water
 Make water unfit for consumption.
 Agrochemicals in water diffuse with larger water bodies to promote the
growth of algae – which can cause organisms such as fish to die. (This
phenomenon is widely called Fish kills)
 Excess chemicals lead to eutrophication.
 Leads to water pollution.
 Alters the chemical properties of water.
Eutrophication.
Eutrophication, defined as the addition of ‘excess’ nutrients to a water body, is a
widespread environmental problem facing the world’s aquatic habitats.
Eutrophication is the process in which a water body becomes overly enriched
with nutrients, leading to the plentiful growth of simple plant life. The excessive
growth (or bloom) of algae and plankton in a water body are indicators of this
process. Eutrophication is considered to be a serious environmental concern since
it often results in the deterioration of water quality and the depletion of
dissolved oxygen in water bodies. Eutrophic waters can eventually become “dead
zones” that are incapable of supporting life.
Aquatic ecosystems are home to several plant and animal life forms – both simple
and complex. The process of eutrophication destroys the balance in these
ecosystems by favouring the growth of simple plant life. This greatly decreases
the biodiversity of the ecosystem by killing off several desirable species.

Causes of Eutrophication
The availability of nutrients such as nitrogen and phosphorus limits the growth of
plant life in an ecosystem. When water bodies are overly enriched with these
nutrients, the growth of algae, plankton, and other simple plant life is favoured
over the growth of more complex plant life.

How do Water Bodies Become Overly Enriched?


Phosphorus is considered one of the primary limiting factors for the growth of
plant life in freshwater ecosystems. Several sources also claim that the
availability of nitrogen is an important limiting factor for the growth of algae.
Phosphates tend to stick to the soil and are transported along with it. Therefore,
soil erosion is a major contributor to the phosphorus enrichment of water bodies.
Some other phosphorus-rich sources that enrich water bodies with the nutrient
include:

 Fertilizers
 Untreated sewage
 Detergents containing phosphorus
 Industrial discharge of waste.
Among these sources, the primary contributors to eutrophication include
agriculture and industrial wastes.

What Happens to the Huge Biomass of Algae in Eutrophic Waters?


The excessive growth of algae in eutrophic waters is accompanied by the
generation of a large biomass of dead algae. These dead algae sink to the bottom
of the water body where they are broken down by bacteria, which consume
oxygen in the process.
Process of Eutrophication
The overconsumption of oxygen leads to hypoxic conditions (conditions in which
the availability of oxygen is low) in the water. The hypoxic conditions at the
lower levels of the water body lead to the suffocation and eventual death of larger
life forms such as fish.

Classification of Eutrophication
The process of eutrophication can be categorized into two types based on its root
cause. Both these types are explained in this subsection.

Anthropogenic Eutrophication
Anthropogenic eutrophication is caused by human activity – Agricultural farms,
golf courses, lawns, etc. are supplied with nutrients by humans in the form of
fertilizers. These fertilizers are washed away by rains and eventually find their
way into water bodies such as lakes and rivers.
When introduced to an aqueous ecosystem, the fertilizers supply plentiful
nutrients to algae and plankton, resulting in the eutrophication of the water body.
Overpopulation places a huge demand on industrial and agricultural expansion,
which in turn leads to deforestation. When this occurs, the soil erodes more
easily, resulting in increased soil deposits in water bodies. If the soil is rich in
phosphorus, it can lead to eutrophication and severely damage the ecosystem in
and around the water body.
When sewage pipes and industrial wastes are directed to water bodies, the
nutrients present in the sewage and other wastes increase the rate at which
eutrophication occurs.

Natural Eutrophication
Natural eutrophication refers to the excessive enrichment of water bodies via
natural events. For example, the nutrients from the land can be washed away in a
flood and deposited into a lake or a river. These water bodies become overly
enriched with nutrients, enabling the excessive growth of algae and other simple
plant life.
The process of natural eutrophication is much slower when compared to the
process of anthropogenic eutrophication. This process is also somewhat
dependent on the temperature of the environment. It may even be complemented
by the temperature changes brought on by global warming.

Effects of Eutrophication
Primarily, the adverse effects of eutrophication on aquatic bodies include a
decrease in biodiversity, an increase in toxicity of the water body, and a change
in species dominance. Some other important effects of this process are listed
below.

 Phytoplanktons grow much faster in such situations. These phytoplankton


species are toxic and are inedible.
 Gelatinous zooplankton blooms fast in these waters.
 Increased biomass of epiphytic and benthic algae can be observed in
eutrophic waters.
 Significant changes arise in the species composition of macrophytes and
the biomass.
 The water loses its transparency and develops a bad smell and colour. The
treatment of this water becomes difficult.
 Depletion of dissolved oxygen in the water body.
 Frequent fish kill incidents occur and many desirable fish species are
removed from the water body.
 The populations of shellfish and harvestable fish are lowered.
 The aesthetic value of the water body diminishes significantly.

An image detailing the change in the quality of water in eutrophic water bodies
is provided above.

Ecological Effects of Eutrophication


Natural standing waters range from ultra oligotrophic to eutrophic with a
progressive increase in productivity and related parameters. In addition to such
general changes, eutrophication also affects the vertical structure of lakes with
further implications for the biology of freshwater organisms. The transition
from eutrophic to hypertrophic status is usually the result of human activities,
and ultimately affects the whole ecological balance of the freshwater system.

Decrease in Biodiversity
When an aquatic ecosystem is enriched with nutrients by either natural or
artificial means, the conditions become extremely beneficial to primary
producers. Commonly, algae and other similar species utilize these nutrients and
a huge increase in their population (algal bloom) is observed.
These algal blooms hinder the flow of sunlight to the bottom of the aquatic body
and also cause wide swings in the dissolved oxygen levels in the water.
When the dissolved oxygen in the water reduces to an amount below the hypoxic
level, many marine animals suffocate and die. This reduces the effective
biodiversity of the water body.

Increase in Water Toxicity


A few algae are toxic to many plants and animals. When these algae bloom in
eutrophic waters, they release neurotoxins and hepatotoxins. These toxins can
also move up the food chain via shellfish or other marine animals and lead to the
death of many animals.
Toxic algal blooms can also be harmful to humans and are the root cause of many
cases of neurotoxic, paralytic, and diarrhoetic shellfish poisoning.

Invasion of New Species


A limiting nutrient corresponding to a water body can be made abundant by the
eutrophication process, leading to a shift in the species composition of the aquatic
body and the ecosystem surrounding it.
If a nitrogen-deficient water body is suddenly enriched with it, many other
competitive species might relocate to the water body and out-compete the original
inhabitants of the ecosystem. One such example of a new species invading
eutrophic conditions is the common carp, which has adapted to these conditions.
Eutrophication is the world’s most widespread water quality problem, occurring
in fresh waters of all continents with the exception of Antarctica and in
developed and developing countries alike. Although eutrophication may be
observed in rivers and indeed riverine discharges from sewage treatment works
are a common source of freshwater fisheries ecology.

Effect on Air

 Pesticide particles diffuse with air, altering their composition.


 Winds disperse polluted air across large areas, spreading their ill effects.
 Increases risk of respiratory illnesses.
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EFFECTS OF AGROCHEMICALS ON HUMAN HEALTH
Pesticides can cause short-term adverse health effects, called acute effects, as
well as chronic adverse effects that can occur months or years after exposure.
Examples of acute health effects include stinging eyes, rashes, blisters,
blindness, nausea, dizziness, diarrhea and death. Examples of known chronic
effects are cancers, birth defects, reproductive
harm, immunotoxicity, neurological and developmental toxicity, and disruption
of the endocrine system.
Some people are more vulnerable than others to pesticide impacts. For example,
infants and young children are known to be more susceptible than adults to the
toxic effects of pesticides. Farm workers and pesticide applicators are also more
vulnerable because they receive greater exposures.
For more information about the effects of specific chemicals or pesticide
products, see Pesticide Action Network’s Pesticide Database. For a survey of
scientific studies linking pesticides to specific diseases, see Beyond Pesticides’
Pesticide-induced diseases database.
Acute (Immediate) Health Effects
Immediate health effects from pesticide exposure includes irritation of the nose,
throat, and skin causing burning, stinging and itching as well as rashes and
blisters. Nausea, dizziness and diarrhea are also common. People with asthma
may have very severe reactions to some pesticides, particularly
pyrethrin/pyrethroid, organophosphate and carbamate pesticides.

In many cases, symptoms of pesticide poisoning mimic symptoms of colds or


the flu. Since pesticide-related illnesses appear similar or identical to other
illnesses, pesticide poisonings are often misdiagnosed and under-reported.
Immediate symptoms may not be severe enough to prompt an individual to seek
medical attention, or a doctor might not even think to ask about pesticide
exposure. Still, seek medical attention immediately if you think you may have
been poisoned by pesticides.
Chronic (Long-term) Health Effects
Chronic health effects include cancer and other tumors; brain and nervous
system damage; birth defects; infertility and other reproductive problems; and
damage to the liver, kidneys, lungs and other body organs. Chronic effects may
not appear for weeks, months or even years after exposure, making it difficult to
link health impacts to pesticides.
Pesticides have been implicated in human studies of leukemia, lymphoma and
cancers of the brain, breasts, prostate, testes and ovaries. Reproductive harm
from pesticides includes birth defects, still birth, spontaneous
abortion, sterility and infertility.
Endocrine disruptors are chemicals that — often at extremely low doses
— interfere with important bodily functions by mimicking or blocking
hormones (the chemical messengers that circulate in blood and regulate many
body processes including metabolism, brain development, the sleep cycle and
stress response). Some pesticides act as endocrine disruptors and have been
shown to cause serious harm to animals, including cancer, sterility and
developmental problems. Similar impacts have been associated with human
exposure to these chemicals.
Children are More Vulnerable to Pesticide Exposure
Children are not simply “little adults.” Children are more vulnerable to pesticide
exposure because their organs, nervous systems and immune systems are still
developing. Children are also less able to detoxify and excrete
pesticides. Exposure during certain early development periods can cause
permanent damage.
In addition to being more vulnerable to pesticide toxicity, children’s behavior
and physiology make them more likely to receive greater pesticide
exposure than adults. Most pesticide exposure occurs through the skin and
children have more skin surface for their size than adults. Children have a
higher respiratory rate and so inhale airborne pesticides at a faster rate than
adults. Children also consume proportionately more food and water — and
pesticide residues — than adults. With their increased contact with floors, lawns
and playgrounds, children’s behavior also increases their exposure to pesticides.
Health Effects of Certain Classes of Pesticides
Organophosphates & Carbamates:
These pesticides are like nerve gas: they attack the brain and nervous
system, interfering with nerve signal
transmission. Symptoms include headaches, nausea, dizziness, vomiting, chest
pain, diarrhea, muscle pain and confusion. In severe poisoning incidents,
symptoms can include convulsions, difficulty breathing, involuntary urination,
coma and death. Acute poisoning of the nervous system by these pesticides
affects hundreds of thousands of people around the world each year.
Soil Fumigants:
These pesticides are applied to soil, forming a gas that is toxic to nematodes,
fungi, bacteria, insects, and plants in the soil. Because they are gases, they move
from the soil into the air and expose people living or working
nearby. Commonly used soil fumigants in California include 1,3-
dichloropropene, chlorpicrin, metam sodium, and metam potassium. Symptoms
of fumigant exposure include irritation of skin, eyes, and lungs
(dichloropropene and chloropicrin), and extremely irritating to eyes and lungs
(metam sodium and metam potassium). Dichloropropene, metam sodium, and
metam potassium are all cancer causing chemicals and metam sodium causes
reproductive harm. In counties where fumigant use is high, premature birth
is more common than in counties with low fumigant use.
Pyrethroids:
These insecticides are synthetic chemicals that are structurally similar to
botanical compounds but have been designed to be more persistent. They are
toxic to the nervous system, and there is concern that during pregnancy a fetus
is not able to efficiently break down these chemicals. Symptoms of pyrethroid
poisoning include tremors, salivation, headache, fatigue, vomiting, stinging and
itching skin, and involuntary twitching. Many pyrethroids also cause long term
health problems. For example, resmethrin causes both cancer and reproductive
harm. Cypermethrin, fenvalerate, and deltamethrin all cause genetic damage and
reproductive harm. Data from the Center for Disease Control and Prevention’s
national biomonitoring program links pyrethroid exposure to heart disease.

PLANT GROWTH REGULATORS & BACKGROUND CHEMISTRY


Plant growth regulators are the chemical substances which govern all the factors
of development and growth within plants. Some other names used to refer to it
are phytohormones and plant growth hormones.
Phytohormones are organic compounds which are either synthesized in
laboratories or produced naturally within the plants. They profoundly
control and modify the physiological processes like the growth,
development, and movement of plants.
Based on their actions, plant growth regulators are broadly classified into
two major groups:
 Plant growth promoters
 Plant growth inhibitors.
Auxins, Gibberellins, and Cytokinins are grouped into Plant growth
promoters while Abscisic acid and Ethylene are grouped into Plant growth
inhibitors.
Ethylene can be grouped either into the promoters or into the plant
inhibitors.

Discovery of Plant Growth Regulators


Though it was serendipity, initial steps of the discovery of major plant
growth regulators began with Charles Darwin and his son, Francis Darwin.
They observed the growth of coleoptiles of canary grass towards the light
source-phototropism. Followed by a series of experiments, they concluded
the presence of a transmittable substance that influences the growth of
canary grass towards the light. That transmittable substance was what we
know as auxin which was isolated later by F.W. Went.

Effect of Auxin on Plant Growth


Later, many scientists discovered and isolated different plant growth
regulators. Gibberellins or gibberellic acid was formerly found in uninfected
rice seedlings and was reported by E. Kurosawa. F. Skoog and Miller
discovered another growth-promoting substance named kinetin, which is
now known as cytokinins.

Characteristics of Plant Growth Regulators


As the plants require oxygen, water, sunlight, and nutrition to develop and
grow, they do require certain chemical substances to manage their growth
and development. These chemical substances are known as Plant Growth
Regulators and are naturally produced by the plants itself.
These are simple organic molecules having several chemical
compositions. They are also described as phytohormones, plant growth
substances, or plant growth hormones.
They can accelerate as well as retard the rate of growth in plants.
Plants growth hormones or plant growth regulators exhibit the following
characteristics:
1. Differentiation and elongation of cells.
2. Formation of leaves, flowers, and stems.
3. Wilting of leaves.
4. Ripening of fruit.
5. Seed dormancy, etc.
Generally, there are five types of plant hormones, namely, auxin,
gibberellins (GAs), cytokinins, abscisic acid (ABA) and ethylene. In addition
to these, there are more derivative compounds, both natural and synthetic,
which also act as plant growth regulators.
Types of Plant Growth Regulators
Plant growth hormones or regulators are of the following types:

1. Plant Growth Promoters


2. Plant Growth Inhibitors

Plant Growth Promoters


Auxins

The first phytohormone to be discovered is the Auxin and it was discovered


by the biologist Charles Darwin.
Auxins are one of the most important plant hormones. The chief naturally
occurring auxin is indole-3 acetic acid – IAA and other related compounds.
The term Auxin is derived from the Greek language meaning to grow.
These plant growth regulators are generally produced at the points of stems
and roots from where they are transported to other parts of the plants. These
plant hormones include both natural and synthetic sources. Indole-3-acetic
acid and indole butyric acid are obtained from natural plant sources,
whereas naphthalene acetic acid and 2, 4-dichlorophenoxyacetic acid are
obtained from synthetic sources.

Functions of Auxins
1. Facilitate flowering in plants
2. Used in the process of plant propagation.
3. Used by gardeners to keep lawns free from weeds.
4. Involved in the initiation of roots in stem cuttings.
5. Prevention of dropping of leaves and fruits at early stages.
6. Regulate xylem differentiation and assists in cell division.
7. Auxins are widely used as herbicides to kill dicot weeds.
8. Used to produce fruit without preceding fertilization.
9. Promote natural detachment (abscission) of older leaves and fruits.
10. Apical dominance may occur in which the growth of lateral buds is
inhibited by the growth of apical buds. In such cases, the shoot caps
may be removed.
11. These are produced by the apex of root and shoot.

Gibberellins
Gibberellins are an extensive chemical family based on the ent-
gibberellane structure. The first gibberellin to be discovered was gibberellic
acid. Now there are more than 100 types of gibberellins and are mainly
gathered from a variety of organisms from fungi to higher plants.
They are acidic and are denoted as follows – GA1, GA2, GA3etc.

Functions of Gibberellins
1. Delay senescence in fruits.
2. Involved in leaf expansion.
3. Break bud and seed dormancy.
4. Promote bolting in cabbages and beet.
5. Facilitate elongation of fruits such as apples and enhance their
shape.
6. Used by the brewing industry to accelerate the malting process.
7. Used as the spraying agent to increase the yield of sugarcane by
elongation of the stem.
8. In young conifers, utilized to fasten the maturity period and facilitate
early seed production
9. Helps in increasing the crop yield by increasing the height in plants
such as sugarcane and increase the axis length in plants such as
grape stalks.
10. Gibberellins are acidic in nature.
11. It also delays senescence.

Cytokinins

These are produced in the regions where cell division occurs; mostly in the
roots and shoots. They help in the production of new leaves, lateral shoot
growth, chloroplasts in leaves etc. They help in overcoming apical
dominance and delay ageing of leaves.

Functions of Cytokinins
1. Break bud and seed dormancy.
2. Promotes the growth of the lateral bud.
3. Promotes cell division and apical dominance.
4. They are used to keep flowers fresh for a longer time.
5. Used in tissue culture to induce cell division in mature tissues.
6. Facilitate adventitious shoot formation and lateral shoot growth.
7. Promotes nutrient mobilization that in turn assists delaying leaf
senescence.
8. Helps in delaying the process of ageing (senescence) in fresh leaf
crops like cabbage and lettuce.
9. Involved in the formation of new leaves and chloroplast organelles
within the plant cell.
10. Used to induce the development of shoot and roots along with auxin,
depending on the ratio.

Plant Growth Inhibitors


Abscisic acid
It is a growth inhibitor, which was discovered in the 1960s. It was initially
called dormant. Later, another compound abscisin-II was discovered and
are commonly called as abscisic acid. This growth inhibitor is synthesized
within the stem, leaves, fruits, and seeds of the plant. Mostly, abscisic acid
serves as an antagonist to Gibberellic acid. It is also known as the stress
hormone as it helps by increasing the plant-tolerance to various types of
stress.

Functions of Abscisic acid


1. Stimulates closing of stomata in the epidermis.
2. Helps in the maturation and development of seeds.
3. Inhibits plant metabolism and seed germination.
4. It is involved in regulating abscission and dormancy.
5. It is widely used as a spraying agent on trees to regulate dropping of
fruits.
6. Induces seed-dormancy and aids in withstanding desiccation and
various undesired growth factors.

Ethylene
Ethylene is a simple, gaseous plant growth regulator, synthesised by most
of the plant organs includes ripening fruits and ageing tissues. It is an
unsaturated hydrocarbon having double covalent bonds between and
adjacent to carbon atoms.
Ethylene is used as both plant growth promoters and plant growth
inhibitors. Ethylene is synthesized by the ripening fruits and ageing tissues.
Functions of Ethylene
Ethylene is the most widely used plant growth regulator as it helps in
regulating many physiological processes.
1. Induce flowering in the mango tree.
2. Promotes sprouting of potato tubers.
3. Breaks the dormancy of seeds and buds.
4. Enhances respiration rate during ripening of fruits.
5. Applied to rubber trees to stimulate the flow of latex.
6. Facilitates senescence and abscission of both flowers and leaves.
7. Used to stimulate the ripening of fruits. For example, tomatoes and
citrus fruits.
8. Affects horizontal growth of seedlings and swelling of the axis in dicot
seedlings.
9. Increases root hair formation and growth, thus aids plant to expand
their surface area for absorption.

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