Chemical Control Methods in Pest Management PDF

Lesson 4.1: Chemical Control Methods in Pest Management  Chemical Control Generally called pesticides Strictly speaking, pesticides supposedly applies only to chemicals that kill pests. However, at present, pesticides can include those chemicals that do not necessarily kill...

Lesson 4.1: Chemical Control Methods in Pest Management  Chemical Control Generally called pesticides Strictly speaking, pesticides supposedly applies only to chemicals that kill pests. However, at present, pesticides can include those chemicals that do not necessarily kill the pests directly such as insect growth regulators or pathogen growth inhibitors Very common practice in the Philippines  Chemical Control Pesticide is a toxic chemical substance or a mixture of substances or biological agents intentionally released into the environment to control and destroy pests Pesticides are either: A chemical substance (chemical pesticide) could be synthetic organic compounds (e.g., organochlorines, organophosphorus, and carbamates)  Chemical Control Pesticides are either: A biological agent or microbial agents (biopesticide) such as Bacillus thuringiensis (Aztron or Thuricide) or baculovirus, used in insect control An antimicrobial agent/compounds or disinfectants used to disinfect seeds and postharvest products, A botanical compounds such as pyrethrins (from chrysanthemum), nicotine (from tobacco), and rotenone (from Derris) Synthetic pyrethroids, nicotinoids, and rotenoids (synthesized from petroleum-based chemicals)  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 1. Target organism (the pest they control)  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 2. Sources of origin chemical pesticides biological or biopesticides - derived from natural materials such as animals, plants, and microorganisms (bacteria, viruses, fungi, and nematodes). - more host-specific, less toxic to non-target organisms, and environmentally friendly than chemical pesticides.  Pesticide Classification  Pesticide Classification 2. Sources of origin biological or biopesticides They are classified into three groups: a) microbial pesticides, b) botanical pesticides, and c) biochemical pesticides.  a. Microbial Pesticides Microbial pesticides could be the microorganism itself or a toxin, or any product from microorganisms - Bacillus thuringiensis (Dipel, Thuricide, Aztron)  b. Botanical Pesticides Organic pesticides derived from plants (pyrethrins, rotenone, nicotine, sabadilla, ryania) Pyrethrins - refined 6 esters obtained from pyrethrum extracted from chrysanthemum (Tanacetum genus) Pyrethroids - synthetic compounds produced to mimic the effects of the pyrethrin esters Other synthetics copied from botanicals Rotenoids and nicotinoids – synthetic forms of rotenone and nicotine. Ex. imidacloprid (Confidor or Winner) and thiamethoxam (Actara) effective against thrips, leafhoppers, whiteflies, cutworms etc. Derris elliptica (tubli) extract contain rotenone Caused convulsions and death of insects Tobacco extract has nicotine the source of the copied synthetic chemical nicotinoid a contact poison that affect the nerves causing death Other synthetics copied from botanicals Sabadilla (from seeds of Schoenocaulon officinale (Liliaceae)) contact and stomach poison It affects the nerves causing death of caterpillars, leafhoppers, thrips, stink bugs, and squash bugs attacking vegetables Other synthetics copied from botanicals Azadiractin obtained from neem tree Azadiracta indica tree's bark, leaves, and fruits, but seeds have the highest concentration (Neemcure, Azatin, and Azadin) Other synthetics copied from botanicals Ryania obtained from the roots and stems of Ryania speciosa (Flacourtiaceae) This alkaloid is useful as a contact or stomach poison and directly prevents muscles from contracting, causing paralysis.  The majority of the insecticidal plants are insect deterrents or repellents and insect growth regulators (IGRs) rather than insecticidal IGRs mimic hormones in young insects and disrupt their growth and reproduction or affects metamorphosis, causing malformations, sterility, and death.  c. Biochemical Pesticides natural materials with nontoxic mechanisms to control pests. Example: insect sex pheromones  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 3. Based on Toxicity Usually expressed in LD50 (Median Lethal Dose) that produces death in 50% of exposed animals and LC50 (50 % lethal concentration)  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 4. Based on their chemical composition and nature of A.I. The most common and useful method of classifying pesticides 1. Natural insecticides are either plant-based or from mineral oils. 2. Synthetic insecticides are also either inorganic or organic in origin, but most are of organic origin. Organic insecticides are categorized into four kinds. 1) organochlorines, 2) organophosphates, 3) Different kinds of Insecticides and examples  Organochlorines Also known as chlorinated hydrocarbons. They were extensively used in the 1940s through 1960. Some were banned in advanced countries like the US because of persistence or long-term residual effect in the environment DDT, BHC  Organophosphates or organophosphorus pesticides are derivatives of phosphoric acid are formulated either as: a stomach poison, contact poison, fumigant poison leading to nerve poisons.  Organophosphates or organophosphorus pesticides These pesticides are biodegradable, causing minimum environmental pollution but are potentially toxic to various non-target species affecting the nervous impulses leading to paralysis and death Malathion, Parathion, Diazinon, Dichlorvos  Carbamates Similar to organophosphates but are derived from carbamic acid while organophosphates from phosphoric acid. Used as stomach and contact poisons and affect the nerves resulting in death. Sometimes, they are used as a fumigant.  Carbamates They can be easily degraded in the natural environment with minimum environmental pollution. Examples are carbaryl (Sevin), carbofuran (Furadan), and propoxur (one of Baygon products)  Synthetic pyrethroids Synthesized by duplicating the structure of natural pyrethrins. Relatively more stable with more prolonged residual effects. are highly toxic to insects and fish but slightly toxic to mammals and birds. Most are non-persistent and got broken easily on exposure to light and considered the safest insecticides for use. E.g. Allethrin and Permethrin Synthetic pyrethroids  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 5. Based on the Mode of Action 1. physical poison (e.g., heavy mineral oils and inert dust), 2. protoplasmic poison (e.g., Arsenicals), 3. heavy metals (e.g., Hg and acids), 4. respiratory poison (e.g., hydrogen cyanide, rotenone, dinitrophenols), 5. nerve poison (e.g., organophosphates such as malathion); 6. chitin synthesis inhibitors (e.g., diflubenzuron), and 7. stomach poison (e.g., Bt formulation).  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 6. Based on Selectivity Broad-spectrum pesticides kill a wide range of pests and other non-target organisms. Broad-spectrum insecticide is chlorpyrifos (Dursban) Broad-spectrum herbicide is glyphosate (Roundup)  Pesticide Classification 6. Based on Selectivity Selective or narrow-spectrum pesticides kill only a specific or group of pests leaving other organisms unaffected or with little effect. Examples of selective insecticide are Pirimicarb with aphids as target. Example of selective herbicide 2, 4-D affects broad-leaved plants leaving the grassy crops unaffected  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 7. Based on Type of Formulation Pesticide formulations are a mixture of: 1. active ingredient (a.i.) - chemicals that aimed to control target pests 2. inert ingredients - materials added to the a.i. to make pesticides safer, more effective, and easier to measure, mix, and apply or store longer to increase shelf life (water, petroleum solvent, wetting agents, spreaders, stickers, and extenders) Pesticide Classification  Pesticide Classification 7. Based on Type of Formulation Three main types: 1. Solid 2. Liquid 3. Gas Some formulations are ready for use, while others need further dilution.  Solid formulations In granules, the active ingredient is mixed with inert clays to form particles of various sizes. Granular formulations are prepared for direct application and require specialized dispersal equipment, scattered by hand or small hand-cranked units. Examples are Imidacloprid 5G (Merit) and carbofuran (Furadan 3G);  Solid formulations Dust formulations are finely ground mixtures of the active ingredient and an inert carrier such as clay, talc, silica gel, pyrophyllite, diatomaceous earth, bentonite, hydrated lime, or kaolin. They are intended for direct application without further mixing. E.g., Permethrin Dust and Bt or Dipel Dust  Miscellaneous formulations Ultra-low volume concentrates (ULV) - are in their original liquid form dissolved in a small amount of solvent These concentrates may approach 100% active ingredients. E.g., Endosulfan for combating cotton and rice pests  Miscellaneous In baits formulations - the active ingredients are mixed with pest food or attractant. They can also control birds, ants, slugs, snails, and agricultural pests such as crickets and grasshoppers. Examples of insecticide baits contain active ingredients such as imidacloprid, dinotefuran, nicotinoid, and abamectin to control cockroaches, ants, and flies  Pesticide Classification 1. target organism (the pest they control) 2. sources of origin 3. toxicity 4. chemical structure 5. mode of action (the way they control the pest) 6. selectivity 7. physical state or formulation 8. mode of entry  Pesticide Classification 8. Based on Mode of Entry According to the mode of entry to the insect pest body in case of insecticides or plants in case of herbicides, pesticides are classified as 1) systemic pesticides, 2) non-systemic or contact poisons, 3) stomach poisons, 4) fumigants and repellents  Systemic pesticides Absorbed by plants or animal hosts and transfer to untreated tissues. Systemic herbicides penetrate plant tissues and move through the vascular system killing weeds with partial spray coverage. Examples: Acephate (Orthene®), imidacloprid (Bayer's Tree & Shrub Insect Control™, Merit®), and dinotefuran (Greenlight Tree and Shrub Insect Control™, Safari®). Examples of systemic herbicides are 2, 4-D), and glyphosate (Roundup).  Contact pesticides Must come into physical contact with the pest to be effective. Upon contact, the pesticide enters the body of pests via their epidermis and causes death by poisoning. Examples of contact herbicides are paraquat and diquat dibromide. Examples of contact insecticide include carbaryl (Sevin®), fipronil (Over 'N Out®), pyrethrins, pyrethroids lambda- cyhalothrin, permethrin, and liquid fipronil or spinosad Stomach poisons Stomach poisons enter the pest's body through their mouth and digestive system and cause death by poisoning. They are applied as sprays or dust onto the leaves and stems of plants and eaten by the target insects Examples are Paris green, lead arsenate, calcium arsenate, and fluorine compounds, including sodium fluoride and cryolite.  Fumigants pesticides that form poisonous gases when applied. They enter through the insect spiracles and cause death by poisoning. Some of their active ingredients are liquids when packaged under high pressure but change to gases when released. Common fumigants used to treat stored products or nursery stock include hydrogen cyanide, naphthalene, nicotine, and methyl bromide. Soil fumigants commonly used as nematicides are methyl bromide, dichloropropane, propylene oxide, dibromochloropropane, organophosphate insecticides chloropicrin.  Repellents do not kill but are distasteful enough to keep pests away from treated areas/commodities. They also interfere with pest's ability to locate crop. Examples are pyrethrin, Bifenthrin, and Talstar P  Herbicides chemicals used for destroying unwanted vegetation or weeds (Vats 2015). The herbicide is still the most prominent product type accounting for 47.6 % of global pesticide sales, followed by insecticide (29.4 %), fungicides (17.5), and others (5.5%) (CLS 2000).  Classification of Herbicides Herbicides are classified based on: 1) translocation, 2) timing of application, 3) method of application 4) specificity  1. Based on Translocation Systemic herbicides (translocated) - extensively translocated in the plant through the vascular system and water, nutrients, and other materials from absorption to action sites. E.g., Glyphosate and Glufosinate Non-systemic herbicides (contact) - kill only the portion of plant tissue in contact; therefore, it must be applied uniformly to be effective. These are comparatively fast-acting herbicides, e.g., bromoxynil and bentazon are contact herbicides.  Classification of Herbicides Herbicides are classified based on: 1) translocation, 2) timing of application, 3) method of application 4) specificity  2. Based on Time of Application Preplant herbicides are non-selective herbicides applied to the soil before planting. (met am-sodium and dazomet). Pre-emergence herbicides are applied before the weed seedlings emerge through the soil surface. E.g. (Dithiopyr and Pendimethalin). Post-emergence herbicides are applied after weed seedlings have emerged through the soil surface. Must not be made when there is rain making them ineffective. (is 2,4-D)  Classification of Herbicides Herbicides are classified based on: 1) translocation, 2) timing of application, 3) method of application 4) specificity  3. Based on Method of Application Soil herbicides are applied to the soil and are used as pre- plant or pre-emergence treatment. (thiocarbamates and trifluralin). Foliar herbicides, on the other hand, are generally post- emergence and can either be translocated (systemic) throughout the plant or at a specific site. (Glyphosate, and 2,4- D).  Classification of Herbicides Herbicides are classified based on: 1) translocation, 2) timing of application, 3) method of application 4) specificity  4. Based on Specificity Selective Herbicides control or suppress individual plants without affecting the growth of other species. (2,4-D, mecoprop, dicamba ) - control broadleaf weeds but remains ineffective against grasses. Non-selective Herbicides kill all kinds of weeds. (Paraquat, glufosinate, glyphosate).  Fungicides Fungicides are chemicals or biological agents that kill or inhibit fungi, including the fungal-like organisms like the Oomycetes. Chemicals that inhibit but do not kill fungi (only inhibit its growth, sporulation, or spore germination) are also called "fungistats."  Classification of Fungicides Fungicides are classified based on: 1) Origin 2) Mode of action 3) Their general uses  1. Based on Origin Bio-fungicides contain living microorganisms (bacteria, fungi) that are antagonistic to plant pathogens. E.g., Eco guard contains Bacillus licheniformis; Bio-Trek 22G contains Trichoderma harzianum. In the Philippines, we have Serenade, a bio-organic fungicide with Bacillus subtilis strain QST 713 as the active ingredient. Chemical fungicides are synthesized from organic and inorganic chemicals.  Classification of Fungicides Fungicides are classified based on: 1) Origin 2) Mode of action 3) Their general uses  2. Based on the Mode of Action 1. Protectants are effective only when applied before the fungal infection occurs. Examples are zineb, mancozeb, and sulfur. 2. Therapeutants can eradicate a fungus after it has caused the infection and curing the plant. Examples are carboxin, oxycarboxin, and Aureofungin antibiotic. Usually, chemotherapeutant are systemic in their action and affect the deep-seated infection.  2. Based on the Mode of Action 3. Eradicant fungicides remove pathogenic fungi from the site of infection. E.g., organic mercurials, lime sulfur, and iodine. These chemicals eradicate the host's dormant or active pathogen. They remain useful on or in the host for some time.  Classification of Fungicides Fungicides are classified based on: 1) Origin 2) Mode of action 3) Their general uses  3. Based on their General Uses 1. Seed protectants: Eg. captan, thiram, organomercuries carbendazim, and carboxin. 2. Soil fungicides - applied to the soil. They are used as a pre-plant treatment, e.g., Bordeaux mixture, copper oxychloride, chloropicrin, Formaldehyde, and Vape. 3. Foliage and blossom fungicides, e.g., Captan, ferbam, zineb, protectants mancozeb, and chlorothalonil. 4. Tree wound dresser, e.g., is Bordeaux mixture, while antibiotic examples are cytidine, griseofulvin, streptomycin  Rodenticides Rodenticides are pesticides that kill rodents that include rats and mice, and squirrels. usually formulated as baits, designed to attract animals. Flavorings added may be attractive to children and pets, so they should never be used or stored within their reach of children Rodenticides based on mode of action 1. Acute Poisons- allows quick in killing rodent pests, but rats develop bait shyness, E.g., zinc phosphide, bromethalin, cholecalciferol, and strychnine. 2. Chronic Rodenticide (Anticoagulant) – Kills rodents slowly. Cause internal bleeding after several days of feeding to the poison. It needs repeated ingestion for several days leaving the rodents to grow weaker daily. E.g., warfarin, bromadiolone, chlorophacinone, difethialone, brodifacoum  Molluscicides Molluscicides are pesticides against mollusks, They are also known as snail baits, snail pellets, or slug pellets, which damage crops or other valued plants by feeding on them. Molluscicides include Metal salts such as iron(III) phosphate, aluminum sulfate, and ferric sodium EDTA, which are relatively nontoxic and used in organic gardening.  Molluscicides Metaldehyde and methiocarb are acetylcholinesterase inhibitors, highly toxic to other animals and humans, also acts as a contact poison  Advantages of Chemical Disadvantages of Pesticides Chemical Relatively low cost Easy to apply EffectPesticides on non-target organisms Fast acting “knockdown Pest resurgence - rapid effect” reappearance of a pest Readily available in the population in injurious market numbers, usually brought Limited damage is about after applying a broad- done to crops if applied spectrum pesticide that has at the right killed the natural enemies that concentration normally keep a pest in check  Disadvantages of Chemical Pesticides Pesticide resistance. Pests become resistant to pesticides and are useful only for a short period. In this case, the pest mutates and becomes immune to a substance, so it no longer affects it calls for the use of another pesticide. Persistence or accumulation in the environment (biomagnification) - pesticides stay in the environment for long, accumulates in the food chain, and animals at the top like humans have a greater chance of toxicity due to pesticides' build-up in their system. End of Lesson 4.1