Pesticides

Types, Effects and Benefits of Pesticides

What are Pesticides?


A pest is any type of living organism that causes unwanted effects. Pests include organisms in the following groups: fungi, rodents, weeds, slugs and snails, insects, bird mites, and certain wildlife forms (e.g., moose, rabbits). A pesticide is any material used for killing, controlling or managing pests. Pesticides include products that are used to manage plant growth (e.g., growth regulators). A variety of agricultural pests that can damage crops and livestock and reduce farm productivity are commonly used to eliminate or control it.

History


Sumerians used sulphur compounds to control insects and mites about 4500 years ago, while the Chinese used mercury and arsenic compounds to control body lice about 3200 years ago. Writings from ancient Greece and Rome show that for the control of plant diseases, weeds, insects and animal pests, the use of what can be called chemical methods have been tried. Like various plant extracts such as bitter lupin or wild cucumber smokes were also used against insects. Tar was also used for trapping crawling insects on tree trunks.

Weeds were mainly controlled by hand weeding, but various "chemical" methods such as the use of salt or seawater are also described. Pyrethrum, derived from Chrysanthemum cinerariaefolium's dried flowers "Pyrethrum daisies," has been used for over 2000 years as an insecticide.

Persians used the powder to try and protect stored grain and later Crusaders brought back to Europe relevant information that dried round daisies controlled head lice.

With the discovery of the effects of DDT, BHC, aldrin, dieldrin, endrin, chlordane, captan and 2,4-D, growth in synthetic pesticides accelerated in the 1940s. Due to its broad - spectrum activity, these products were effective and inexpensive with DDT being the most popular.

Research activities in the 1990s focused on finding new members of existing families with higher selectivity and better environmental and toxicological profiles. Moreover, newly developed pesticide families such as triketone and isoxazole herbicides, strobilurin and azolone fungicides and chloronicotinyl, spinosyn, fiprole, diacylhydrazine and triazolopyrimidine insecticides have been launched in the market. Many of the new pesticides could be used in grams instead of kilograms per hectare.

Types of Pesticides


Pesticides can be classified in a number of different ways. Most commonly, they are classified according to:

  • • their target

  • • their mode of action

  • • their chemical structure

  • Let discuss some of the classification types in detail.

    Based on Target Pest


    Pesticides are frequently grouped by the pest they control. Here are some examples of target pest classified pesticide groups.

  • • Fungicide: It controls fungi (moulds, mildews). Eg: benomyl

  • • Herbicide: It kills weeds. E.g.: 2,4-D

  • • Insecticide: Kills insects. E.g.: diazinon

  • • Miticide or Acaricide: Kills mites. E.g: propargite

  • • Nematicide: Kills nematodes (roundworms and hookworms). E.g.: oxamyl

  • • Rodenticide: Kills rodents. E.g: warfarin

  • • Molluscicide: Kills slugs and snails. E.g.: metaldehyde

  • • Avicide: Kills birds. E.g.: avitrol

  • Based on Mode of Action


    It is also possible to group pesticides according to their mode of action - how they enter or affect the target pest. Two examples of pesticide groups are contact pesticides and systemic pesticides in this type of classification.

    Contact pesticides directly kill their targets in contact. For example, if enough of their surface area is covered with a contact herbicide, weeds are killed. Insects can be killed by spraying directly or crawling with contact insecticides across surfaces.
    Systemic pesticides eliminate their targets by being translocated in treated plants. Translocation is the process through which a systemic pesticide moves through a plant being treated. For example, some weeds that receive only limited spray coverage will be killed as a systemic herbicide moves into untreated areas of leaves, stems or roots within the plant. As they feed on the juices that carry systemic insecticides through a plant, some insects may be killed. Some systemic insecticides are carried by treated animals. For example, to control fly larvae in the body, a systemic insecticide may be poured on the backs of beef cattle.

    Based on chemical structure


    Pesticides in the same chemical class or family have a similar chemical structure and typically have a similar mode of action as well as similar symptoms of poisoning, persistence, first aid, clean - up and safety guidelines.Chemical families are:

  • • Organophosphates: Most organophosphates are insecticides, they impair the nervous system by destroying a neurotransmitter.

  • • Carbamates: The carbamate pesticides, like the organophosphorus pesticides, also impair the nervous system by destroying an enzyme that regulates the neurotransmitter. The impacts of the enzyme are usually reversible.

  • • Organochlorine insecticides: Earlier, they were commonly used, but now, due to their health and environmental effects and persistence many countries have been removed from their markets.

  • • Pyrethroid: These are a synthetic version of pyrethrin found in chrysanthemums (Flower), a naturally occurring pesticide. They were developed to maximize their environmental stability.

  • Based on biodegradation
    Pesticides can also be considered as:
  • • Biodegradable: The biodegradable type is those that can be degraded into completely harmless compounds by microbes and other living beings.

  • • Persistent / Non-biodegradable: While the persistent ones may take months or years to break down.

  • Benefits of Pesticides


  • 1. Pesticides increase yields generate more with less land: Farmers have been able to produce larger crops on less land with the introduction of pesticides, increasing crop productivity by 20 to 50 %. Furthermore, pesticides enable farmers to maximize the benefits of other valuable agricultural tools such as seeds of high quality, fertilizers and water resources. Consequently, pesticides are an essential tool for the sustainable production of high - quality food and fibers.

  • 2. Pesticides ensure bountiful harvests: Numerous scientific studies have found that eating fruit and vegetables reduces the risk of many cancers, high blood pressure, heart disease, diabetes, stroke, and other chronic diseases on a regular basis.

  • 3. Pesticides help keep food affordable: Using pesticides, farmers grow more food on the same land. Studies have shown that organic vegetable growers spend considerably more on hand weeding than herbicide growers. This explains why organic foods are more expensive than conventional foods.

  • 4. Pesticides help reduce waterborne and insect transmitted diseases: Such as malaria, the disease of Lyme and virus of West Nile. Pesticides help improve human health by preventing disease outbreaks by controlling populations of rodents and insects.

  • 5. Pesticides help conserve the environment: They allow farmers to produce more crops with less tillage per unit area, thus reducing deforestation, preserving natural resources, and curbing soil erosion. Pesticides are also critical for invasive species and harmful weed control.

  • 6. Herbicides have removed the hardship of hand weeding: This means that farming families around the world have the choice to pursue education and opportunities away from farming, thus bettering living standards and quality of life.

  • 7. Pesticides have transformed developing countries into food producers: In the developing world, crop protection brands have helped farmers grow two or three crops a year, so much so that they can become ' breadbaskets ' for the rest of the world. Agricultural exports benefit people with shorter growing seasons in temperate countries.

  • 8. Securing what’s in storage: It can be attacked by pests even after the crop is in. Precious grains can be harmed by bugs, moulds and rodents. Pesticides used in stored products can extend the product's sustainable life, prevent enormous post-harvest losses from pests and diseases and protect the grain so that it is safe to eat.

  • Effects of Pesticides


  • Pesticides contribute to air pollution: When a pesticide drift occurs and they are suspended in the air and move when the wind blows, it may pollute the air.

  • Contamination of water bodies: Pesticides contaminate every stream of water and more than 90%

  • Killing of aquatic life: When the chemicals in the pesticides reach water bodies, forms of aquatic life such as fish are absorbed or ingested, resulting in organ failure and diseases, eventually killing them. Chemicals can also alter the pH of the water body, thus interfering with normal aquatic life function.

  • Pesticides end up killing the micro-organisms in the soil: With long - term use of pesticides on crops, it will percolate into the soil killing micro-organisms despite their crucial role in breaking down organic substances and helping grow crops.

  • Pesticides can cause diseases which can be chronic: Even after one single consumption, breathing or contact with the skin, pesticides can lead to dangerous and deadly consequences. There are even symptoms that may appear shortly after the chemicals come into contact.

  • Pesticides alter an individuals’ regular functioning: Everyday people are exposed to a combination of pesticides and the reality is that no one is sure of the actual effects of being exposed to even low levels of pesticides consistently. It can often lead to reduced physical activity and changes in the normal functioning of some body organs.

  • Pesticides can damage the ecosystem severely: The use of pesticides can create an imbalance in the energy flow in the ecosystem.