INSECTICIDES, RESISTANCE & PESTICIDES.pptx

This presentation includes a brief note on botanical insecticides, which are plant-derived compounds used to control pests in an eco-friendly way. It also covers insecticide residue, the traces left on crops and in the environment after application, and resistance, where pests evolve to survive chemical treatments. The issue of resurgence of insect pests—a rebound in pest populations after pesticide use—is discussed, along with the environmental degradation of pesticides, highlighting how these chemicals break down and impact ecosystems.

1. BOTANICAL INSECTICIDES, INSECTICIDE RESIDUE,RESISTANCE   RESURGENCE OF INSECT PESTS,  ENVIRONMENTAL DEGRADATION OF PESTICIDES ​

2. BOTANICAL INSECTICIDES Botanical insecticides   are those products used to kill or repel insects, that consist of dried, ground plant material, crude plant extracts, or chemicals isolated from plants. Botanicals are enjoying renewed interest as the popularity of organically-grown food increases  Although botanicals are products of nature, they should not be considered absolutely safe or non-toxic unless so demonstrated. They are active ingredients in certain botanical preparations used as insecticides are relatively toxic to animals and humans . They are insect toxins derived from certain plants, having quick action on target pests, broad spectrum of action and do not persist in the environment. Eg.  Nicotine, Rotenone, Pyrethrum, Neem Products 

3. INSECTICIDE RESIDUE Initial deposit or simply pesticide deposit  is the quantity of pesticide remaining attached to the plant surface or the other surface soon after its application. It progressively decreases due to the chemical breakdown, volatilization and other weathering process. The deposit still remaining at the crop majority is called  pesticide residue or residual deposit . Expressed in parts per million of the fresh weight of the produce. It is seriously harmful to humans   The persisting effect of the residual pesticide is called a  residual effect The maximum permissible insecticide residue level in the harvested product is called  tolerance level.  It depends on the toxicity of the insecticide and the status of the food item

4. Insecticide residues can be maintained below the tolerance level by restricting the application of insecticides, proper use of insecticides, strictly observing the prescribed dosage, time of application and length of the waiting period.(specific interval between the last application and the harvest) The major factor which directly or indirectly influence insecticide residues include       1. The nature of the insecticide and the method of its application        2. Enviromental Factors which affect the dissipation of insecticides      3.  Agricultural practices and plant characters    

5. Steps to reduce toxic residue -  Select insecticides which are less toxic and safest to mammals.  Use non-persistent insecticides (organochlorides on vegetable crops). Avoid the application of insecticides at the time of fruiting. Avoid the over dosage, Apply Uniformly,  Harvest the edible parts only after the expiry of the waiting period.  Thoroughly wash and dry the harvested produce to remove insecticide residues.

6. INSECTICIDE RESISTANCE The development of an ability in strain of insect tolerate doses of toxicants which would prove lethal to majority of individuals in normal population of the same species Insects may exhibit a natural tolerance or can be  due to genetic changes in the pest Behavioristic resistance -  The ability of a pest species to habitually avoid toxic substance.     Eg : avoidance of DDT treated substance by mosquito  Cross Resistance - it is the resistance to more than one insecticide following exposure to only one insecticide compound. it is a kind of pre-adaptation. Physiological resistance -  The resistance developed against organophosphates. It is due to the development of genetically controlled ability in pest to enzymatically hydrolyze the pesticide.     Eg  :the house fly which is resistant to organophosphates the enzyme  Diesterase  gets transformed to      phosphatase by genetic mutation this phosphate degrades organophosphates.

7. DDT resistance in houseflies is the detoxification of DDT to DDE by the enzyme DDT  dihydrochlorinase In India DDT resistance is seen in mosquito  culex  fatigans (1952) ,  the bed bug  cimex lectularius(1953)   and in  singhara  beetle (1963) . The objective of  Insecticide Resistance Managemen t  is to prevent or delay resistance developing to insecticides, or to help regain susceptibility in insect pest populations in which resistance has already arisen. IRM is important in maintaining the efficiency of valuable insecticides.  Insecticide resistance action committee has recommended some guidelines in the use of agrochemical products

8. RESURGENCE OF INSECT PESTS Resurgence is the situation where insecticide application initially reduces an infestation, but soon afterwards the pest rebounds (resurges) to higher levels than before treatment. Replacement, or secondary pest outbreak , is resurgence of non-target pests. It occurs when pesticide is used to control the target pest, but afterwards a formerly insignificant pest replaces the target pest as an economic problem. Pest populations are balanced by the relationship between predators and pests. If predators are removed from or migrate away from a particular environment, opportunistic pest species are able to breed unchecked.

9. It is virtually impossible to annihilate an entire pest population from an area.  Survivors may be safe in areas not covered by the pesticide application or survive sub-lethal doses as a result of uneven pesticide application.  With predators no longer a factor, they are able to multiply very rapidly causing infestations that are worse than ever before. The problem can be addressed through Integrated Pest Management (IPM) strategies.

10. ENVIRONMENTAL DEGRADATION OF PESTICIDE Pesticide degradation   or the breakdown of pesticides pesticide residues in the environment to nontoxic or harmless compounds, usually is beneficial. Persistent pesticides  which primarily consist of organochlorine pesticides, are considered persistent because they are stable in the environment and resist being broken down.  Eg  : DDT, chlordane, endrin, dieldrin Three types of pesticide degradation are microbial, chemical, and photodegradation.

11. Microbial degradation  is the breakdown of pesticides by fungi, bacteria, and other microorganisms that use pesticides as a food source. It occurs in the soil.  Soil conditions such as moisture, temperature, aeration, pH, and the amount of organic matter affect the rate of microbial degradation. Chemical degradation  is the breakdown of pesticides by processes that do not involve living organisms.  Temperature, moisture, pH and adsorption, in addition to the chemical and physical properties of the pesticide, affect degradation process. Photo degradation  is the breakdown of pesticides by   light particularly sunlight. Photodegradation can destroy pesticides on foliage, on the surface of the soil, and even in the air.  The intensity of the sunlight, properties of the application site, the application method and the properties of the pesticide affect the degradation process.

12. They contaminate aquatic environment – killing  phytoplanktons They pollute and poison soil – killing microbes, lower fertility They cause large destruction to non-targeted species and to enemies of pest – disturbs ecological equilibrium They kill insect pollinators, affect agricultural production.  They Enter food chain and cause Biological magnification They interfere with enzyme action, metabolic process, reproductive physiology and behaviour of animals.

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