- Insect control implies everything that make the life hard, tends to kill them and prevents them from increasing in number or spreading.
- Almost everything grown on earth is destroyed by insects.
- Insect control is required to prevent the damage in agriculture, horticulture, and forest products and to protect the human health and that of domestic animals.
Methods of Insect control/Pest control
Physical methods of insect control include use of hands, traps, fire and water, etc. Chemical and Biological are better developed methods.
CHEMICAL CONTROL
- Killing of insects by the use of insecticides
- All the chemical substances that kill the insects by their chemical action are known as insecticides or pesticides.
- Insecticides are widely used in the form of powders, solutes, emulsions, sprays, or fumes.
- Insecticides are divided into 4 major groups based upon physiology and mode of action- stomach poisons, contact poisons, fumigants, and repellents.
1. Stomach poison
- These constitute of toxicants that poison the insect food, which upon ingested are fatal for insects.
- Insects with chewing, sponging, lapping or siphoning mouthparts are killed by such poisons.
Lead arsenate:
- Used to protect the ornamental plants, fruit trees and truck crops from chewing insects.
- Either used as spray or dust.
Sodium arsenate:
- Used in soil poison in termite control.
- Parsis green, Copper-aceto arsenite is used as spray to kill eggs, larva and pupa of mosquitos in rain-bound areas.
Sodium fluoride:
- Water soluble, white powdered compound, used for killing cockroaches and poultry lice.
Sodium fluosilicate:
- Used in Poison baits for moths that destroy garments.
Cryolite
- It is Sodium Aluminum fluorite
- Used as dust or spray on vegetable crops.
2. Contact poisons
- Kills insects on coming direct contact with them.
- Used in control of insects with piercing and sucking mouthparts, can kill insects with other mouthparts type too.
DDT (Dichloro-diphenyl trichloroethane)
- White amorphous powder, insoluble in water, dissolves in most organic solvents (xylene, napthas etc.)
- Used as spray for killing insects’ pests of man and crops.
- Extensively used, being relatively safe, however, houseflies, certain mosquitoes and other arthropods have become immune to it.
BHC (Benzene hexachloride or gammaxene)
- White or chocolate colored powder, insoluble in water, but soluble in organic solvents.
- Used like DDT as sprays for killing mainly aphids on fruit and nut crops.
Malathion
- Dark brown or yellow liquid, smells like garlic.
- Slightly water soluble, miscible with organic solvents.
- Low toxicity to humans, used as alternative to DDT.
Pyrethrum
- Extracted from flowers of Chrysanthemum cinerariafolium.
- Spray to kill household, and livestock pests and certain vegetable pests.
- Kills on mere contact but no residual effect like DDT.
Aldrin
- Found as powder, emulsion, dust, or granules.
- Moderately soluble in mineral oils but highly soluble in organic solvents.
- Used for control of grasshoppers, cotton pests and soil insects.
- Toxic to humans and animals.
Toxophene
- Yellow waxy solid
- Readily soluble in organic solvents, has residual effect.
- Used in killing wide range of pests, affecting crops, vegetables and livestock.
Mineral oils
- Kerosene, crude oils, mobile oil, etc.
- Used to kill mosquito larvae and pupae, scaly insects, mealy bugs, mites etc.
3. Fumigants
- Toxicants used as gases for killing insects in enclosure like warehouses, ships, mills, shop etc.
- Common fumigants are hydrogen cyanide, carbon disulphide, ethylene dichloride, methyl bromide, Sulphur dioxide etc.
4. Repellants
- Substances that repel insects rather than killing them.
- Mildly poisonous
- Trichlorobenzene is used to protect buildings from termites.
- Bordeux mixture and lime ward off leaf hoppers and some chewing insects.
- Oil of cidar protects materials from attack of carpet beetles and clothes moths.
- Pinetar oil (diphenylamine) prevents saw flies from laying eggs in the wounds of animals.
- Mosquito repellants and fly sprays lessen the attacks of blood sucking flies and mosquitoes.
Hazards of Insecticides
- Harmful to human health: Insecticides can be dangerous to people if not handled appropriately. Insecticide exposure can cause skin and eye irritation, respiratory issues, neurological damage, and even cancer.
- Non-target organism poisoning: Although insecticides are intended to kill insects, they can also affect other creatures in the ecosystem, including beneficial insects, birds, fish, and mammals.
- Resistance: Insects can acquire insecticide resistance over time, rendering insecticides less efficient to manage pest populations. This can lead to greater usage of harsher or more toxic pesticides, exacerbating the issues described above.
- Pollution of the environment: Insecticides can pollute soil, air, and water, resulting in pollution of the environment. This can harm the ecology and produce long-term environmental damage.
- Persistence: Many pesticides are tenacious and can linger in the environment for a long period after they have been applied. This might result in a buildup of pesticide residues in the food chain, potentially posing health concerns to people and other animals.
- Disrupt beneficial insect populations: Because insecticides are not species-specific, they can also kill beneficial insects such as bees, butterflies, and ladybugs, which are important for pollination, pest management, and preserving the natural balance of ecosystems.
- Financial strain: The application of pesticides can be costly, resulting in a financial hardship for farmers or homeowners who must purchase and use them on a regular basis to manage pests.
BIOLOGICAL CONTROL
- Most promising weapon against insect control.
- Can be aimed at specific pests without adversely affecting human beings or environment.
Hormones
Hormones have been utilized as a substitute to typical insecticides in insect control. Hormones are molecules made naturally by insects to govern their growth and development. Synthetic versions of these hormones can be used to impair the natural development of insects, preventing them from maturing and reproducing.
There are two types of hormones that are commonly used in insect control:
Juvenile Hormones:
- Prevents insects from reaching adulthood.
- Synthetic versions of juvenile hormones can be used to mimic the natural hormone, causing insects to remain in their juvenile state and preventing them from reproducing.
- Effective against a wide range of insect pests, including mosquitoes, flies, and beetles.
Ecdysone Analogues:
- Ecdysone triggers the molting process in insects.
- Synthetic versions of ecdysone can be used to disrupt the molting process, preventing insects from developing properly and causing them to die.
- Effective against a variety of insect pests, including moths, caterpillars, and mites.
Advantages:
- More specific in their target, meaning that they are less likely to harm beneficial insects or other organisms in the environment.
- Shorter persistence in the environment, meaning that they break down more quickly and have less of an impact on the ecosystem.
Limitations:
- More expensive than traditional insecticides
- Require more frequent application.
- Development of resistance to hormones is possible.
Pheromones
Pheromones are substances that insects naturally make to communicate with one another. They attract mates, mark territory, and warn of danger. Pheromones have also been employed in insect control as an alternative to standard pesticides.
The use of synthetic analogues of pheromones to disturb the normal behavior of insect pests is referred to as pheromone-based insect control. There are two kinds of pheromones used in insect control:
Sex Pheromones:
- Produced by female insects to attract males for mating.
- Synthetic versions of sex pheromones can be used to confuse male insects and prevent them from finding mates.
- Effective against a variety of insect pests, including moths, beetles, and fruit flies.
Aggregation Pheromones:
- Used by some insects to signal the presence of a food source.
- Synthetic versions of aggregation pheromones can be used to attract insects to a specific location, making it easier to monitor and control their populations.
- Effective against a variety of insect pests, including bark beetles and weevils.
Advantages
- More specific in their target
- Shorter persistence in the environment, meaning that they break down more quickly and have less of an impact on the ecosystem.
Limitations
- More expensive
- Development of resistance
Sterilization
Sterilization is a technique used in insect control to diminish or destroy insect problem populations. In sterilization, insects are exposed to radiation or chemicals that render them sterile, preventing them from reproducing. This strategy is frequently used in conjunction with other insect management approaches to diminish or eliminate pest populations.
In insect control, there are two types of sterilizing methods:
Irradiation:
- Exposing insects to high levels of radiation, which damages their reproductive cells and prevents them from reproducing.
- Often used to control the populations of fruit flies, moths, and other insect pests that damage crops.
Chemical sterilization:
- Treating insects with chemicals that disrupt their reproductive processes.
- Done by applying the chemical directly to the insect or by treating the food source of the insect.
- Used to control the populations of mosquitoes, which can transmit diseases such as malaria and dengue fever.
Genetic control
Genetic control is an insect management strategy that includes modifying insect genes to diminish or eradicate pest populations. This method is separated into two categories: suppression and replacement.
Suppression:
- In suppression, the genes of the target insect population are manipulated to reduce their numbers.
- Done by introducing a gene that causes sterility or by introducing a gene that causes the death of the insect at an early age.
- The genetically modified insects are then released into the wild to mate with the wild population, with the goal of reducing the size of the population over time.
- Used to control insect pests that damage crops, such as fruit flies and mosquitoes.
Replacement:
In replacement, the genes of the target insect population are manipulated to replace the wild population with a genetically modified population that is less harmful or has a beneficial effect on the environment.
For example, a genetically modified mosquito can be created that is resistant to the malaria parasite, or a genetically modified beetle can be created that is less harmful to crops. The genetically modified insects are then released into the wild to mate with the wild population, with the goal of replacing the wild population with the modified population over time.
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