Pest Control

Pest Control

• A pest is any living organism that causes damage or discomfort, or transmits or produces disease, and spreads diseases to mankind and harms the environment.
• The three goals of pest management are prevention, suppression, and eradication, aiming for a clean environment and disease-free environment.

Natural Control

• Natural control enhances naturally occurring pest management methods.
• Cultural control makes the crop environment unsuitable for pests to feed, live, or reproduce, and includes methods such as soil tillage, crop rotation, harvest or planting date adjustment, irrigation schemes, variety selection, clean culture, and trap crops.
• Clean culture removes breeding sites or the habitat of the pest, and trap crops attract pests to a localized area where the trap crop is destroyed or treated with a pesticide.

Genetic Control

• Genetic control introduces genetic abnormalities into the eggs of the wild population, exploiting the insect's mating expertise.
• The Sterile Insect Technique (SIT) involves mass rearing of the target insect species (males), sterilizing them with ionizing radiation or chemosterilants, and releasing them in large numbers to reduce the probability of successful matings in the wild population.
• SIT was first described by E.F. Knipling in 1955 and has been successfully used to eradicate screwworm flies, Mexican fruit flies, tsetse flies, and sweet potato weevils from various regions.

Advantages of SIT

• Creates inverse density-dependent feedback, making it more efficient as the wild population decreases.

Insecticides

• Pyrethroid insecticides kill insects by disrupting their nervous systems and are non-persistent and less acutely toxic than organophosphates and carbamates.
• Biological insecticides include plant toxins (e.g., caffeine, nicotine, pyrethrum, and rotenone) and bacterial diseases (e.g., Bacillus thuringiensis), which are environmentally friendly.

Types of Insecticides

• Organophosphates (e.g., Chlorpyrifos, diazinon, and malathion) interfere with the transmission of nerve impulses.
• Chlorinated hydrocarbons (e.g., methoxychlor and dicofol) interfere with the normal movement of potassium and sodium ions across nerve cell surfaces.
• Microbial insecticides consist of microorganisms that attack insects, such as Bacillus thuringiensis.
• Fungal insecticides attack from the outside, growing through the cuticle and exoskeleton, and spreading throughout the body.
• Insecticidal soaps (e.g., potassium salts of fatty acids) dissolve nearby cells, causing cell fluids to leak out and resulting in dehydration and death.
• Oils are used to smother mites, scale insects, and aphid eggs.

Limitations of SIT

• Geography: requires natural barriers or defensible borders to prevent the immigration of the target pest from outside the eradication zone.
• Economics: high cost of rearing, sterilizing, and releasing a large number of insects needs to be justified.
• Desirability of sterile males: lab-reared and sterilized males must be equally or more competitive than native males in mating with native females.
• Knowledge about the pest: reproductive behavior, population dynamics, dispersal, and ecology of the insect are crucial for SIT.
• Timing: development of the lab-reared colony must be synchronous with that of the wild population.
• Resistance: native females may recognize and refuse to mate with sterile males.
• Inherited/delayed sterility: an alternative genetic strategy to SIT, requiring fewer insects and lower doses of radiation.