PESTICIDES
Introduction
Pesticides are chemical, biological, or physical agents used to prevent, destroy, repel, or control pests that damage crops, stored food, human health, and livestock. Pests include insects, weeds, fungi, rodents, nematodes, and microorganisms. The use of pesticides has significantly increased agricultural productivity and helped control vector-borne diseases. However, indiscriminate use has resulted in environmental pollution and health hazards.
Need for Pesticides
To protect crops from pests and diseases
To increase agricultural yield and food security
To reduce post-harvest losses
To control disease vectors such as mosquitoes
To improve quality and market value of crops
Classification of Pesticides
1. Based on Target Organism
a) Insecticides
Used to control insect pests.
Examples:
DDT – controls mosquitoes
Malathion – used against flies and lice
Carbaryl – controls chewing insects
b) Herbicides (Weedicides)
Used to kill unwanted plants.
Examples:
2,4-D – controls broad-leaf weeds
Glyphosate – non-selective herbicide
c) Fungicides
Used to control fungal diseases in plants.
Examples:
Bordeaux mixture – controls grape mildew
Mancozeb – controls leaf spot diseases
d) Rodenticides
Used to kill rats and mice.
Examples:
Zinc phosphide
Warfarin
e) Nematicides
Used to control nematode pests.
Examples:
Aldicarb
Carbofuran
Classification Based on Chemical Nature
1. Organochlorine Pesticides
Highly persistent and accumulate in the environment
Cause biomagnification
Examples: DDT, BHC, Endosulfan
2. Organophosphate Pesticides
Less persistent but highly toxic
Affect nervous system by inhibiting acetylcholinesterase
Examples: Parathion, Malathion, Chlorpyrifos
3. Carbamate Pesticides
Moderate toxicity
Short persistence
Examples: Carbaryl, Aldicarb
4. Synthetic Pyrethroids
Synthetic forms of natural pyrethrins
Effective at low doses
Examples: Cypermethrin, Permethrin
5. Biopesticides
Derived from natural organisms
Environment-friendly
Examples:
Neem (Azadirachtin)
Bacillus thuringiensis (Bt)
Advantages of Pesticides
Increase crop productivity
Protect crops from severe pest attacks
Control vector-borne diseases like malaria and dengue
Reduce storage losses
Improve farmer income and food availability
Harmful Effects of Pesticides
1. Environmental Effects
Soil pollution and loss of beneficial microbes
Water pollution through runoff and leaching
Air pollution during spraying
Destruction of non-target organisms (birds, bees, fish)
Biomagnification (e.g., DDT in food chains)
2. Health Effects
Acute poisoning (vomiting, headache, dizziness)
Chronic effects such as:
Cancer
Nervous disorders
Hormonal imbalance
Pesticide residues in food cause long-term health risks
Biomagnification
Biomagnification is the increase in concentration of pesticides at higher trophic levels of the food chain.
Example:
DDT → plankton → fish → birds → humans
Leads to eggshell thinning in birds like eagles and vultures.
Pesticide Resistance
Repeated use of the same pesticide leads to genetic resistance in pests, making pesticides ineffective and increasing the need for higher doses.
Integrated Pest Management (IPM)
IPM is a sustainable and eco-friendly approach that combines:
Biological control – use of predators (ladybird beetle)
Cultural methods – crop rotation
Mechanical methods – traps
Chemical methods – minimal and need-based pesticide use
Preventive and Control Measures
Use pesticides only when necessary
Follow recommended dosage
Prefer biopesticides
Proper storage and disposal
Use protective clothing
Strict government regulation
Conclusion
Pesticides play a crucial role in modern agriculture, but their misuse causes serious environmental and health problems. The adoption of biopesticides and Integrated Pest Management is essential for sustainable agriculture and environmental protection.
Here are MCQs on Pesticides with answers given after each question (easy for exam practice and quick revision):
MCQs on Pesticides (With Answers)
1. Pesticides are substances used to
A. Increase soil fertility
B. Control pests harmful to crops
C. Increase crop growth
D. Improve climate
✔ Answer: B
2. Which of the following is an insecticide?
A. 2,4-D
B. DDT
C. Bordeaux mixture
D. Warfarin
✔ Answer: B
3. Herbicides are mainly used to control
A. Insects
B. Weeds
C. Fungi
D. Rodents
✔ Answer: B
4. Which pesticide is known to cause biomagnification?
A. Malathion
B. Carbaryl
C. DDT
D. Neem oil
✔ Answer: C
5. Bordeaux mixture is an example of
A. Insecticide
B. Herbicide
C. Fungicide
D. Rodenticide
✔ Answer: C
6. Organophosphate pesticides primarily affect the
A. Digestive system
B. Nervous system
C. Circulatory system
D. Respiratory system
✔ Answer: B
7. Which of the following is a biopesticide?
A. Endosulfan
B. Parathion
C. Bacillus thuringiensis
D. BHC
✔ Answer: C
8. 2,4-D belongs to which group?
A. Insecticide
B. Fungicide
C. Herbicide
D. Rodenticide
✔ Answer: C
9. Pesticide resistance develops due to
A. Seasonal changes
B. Repeated use of the same pesticide
C. Crop rotation
D. Biological control
✔ Answer: B
10. Which method is most eco-friendly for pest control?
A. Excessive pesticide use
B. Integrated Pest Management (IPM)
C. Monoculture farming
D. Chemical spraying
✔ Answer: B
11. Biomagnification refers to
A. Reduction of pesticide toxicity
B. Increase of pesticide concentration at higher trophic levels
C. Breakdown of pesticides in soil
D. Removal of pests
✔ Answer: B
12. Warfarin is used as a
A. Fungicide
B. Herbicide
C. Rodenticide
D. Insecticide
✔ Answer: C
13. Synthetic pyrethroids are
A. Derived from bacteria
B. Highly persistent pesticides
C. Synthetic forms of natural pyrethrins
D. Used only as fungicides
✔ Answer: C
14. Neem-based pesticides are
A. Highly toxic
B. Non-biodegradable
C. Eco-friendly
D. Persistent
✔ Answer: C
15. Which pesticide caused eggshell thinning in birds?
A. Glyphosate
B. DDT
C. Malathion
D. Carbaryl
✔ Answer: B
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