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S2 L2 Insecticides - natural Anna Drew with slide contribution from Martin Wilks, Syngenta, & Rhonda Hamm.

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Presentation on theme: "S2 L2 Insecticides - natural Anna Drew with slide contribution from Martin Wilks, Syngenta, & Rhonda Hamm."— Presentation transcript:

1 S2 L2 Insecticides - natural Anna Drew with slide contribution from Martin Wilks, Syngenta, & Rhonda Hamm

2 Insecticide history Inorganics – arsenic, sulphur Botanicals – pyrethrum Petroleum oils – horticultural/summer/foliar oils Organochlorines (DDT, cyclodienes) Organophosphates (Class 1) Insect growth regulators Pyrethroids (Class 2) Microbial toxins (Bt) Pheromones

3 Importance of Pesticide Regulation PESTICIDE REGULATION is designed to protect the health of those who apply pesticides, those who are exposed as bystanders, and those who are exposed to residues in food and water.

4 Stages of Risk Assessment Toxicological Hazard Assessment Identification of intrinsic toxicological properties and assessment of their relevance to humans

5 World Health Organization (WHO) Classification of Pesticides by Hazard LD 50 for the rat (mg/kg body weight) ClassOralDermal SolidsLiquids SolidsLiquids Ia Extremely hazardous 5 or less20 or less10 or less40 or less Ib Highly hazardous 5 - 5020 - 20010 - 10040 - 400 hazardous 50 - 500200 - 2000100 - 1000400 - 4000 III Slightly hazardous Over 500Over 2000Over 1000Over 4000 II Moderately

6 Key Toxicological Studies Used in Risk Assessment for Pesticide Operators 90 day, sub-acute oral dosing study 21/28 day dermal dosing study Reproductive toxicity studies 1 year oral dosing study (depending on use pattern)

7 Stages of Risk Assessment Toxicological Hazard Assessment Dose-Response Evaluation Determination of quantitative relationships between internal dose and effects for the endpoints of concern

8 The Dose Response Curve

9 Stages of Risk Assessment Toxicological Hazard Assessment Human Exposure Assessment Dose-Response Evaluation Assessment of intensity, frequency, duration and routes of human exposure for the purpose of quanti- fication of internal dose

10 Stages of Risk Assessment Toxicological Hazard Assessment Human Exposure Assessment Risk Characterisation Dose-Response Evaluation Integration of available information to produce conclusions on the probability of adverse effects

11 Early Late Physico-chemical properties Acute oral toxicity, mutagenicity Dermal absorption, inhalation toxicity Subacute & subchronic toxicity Reproductive & developmental toxicity Chronic toxicity, carcinogenicity Toxicology Information in the Development Process

12 Evolution of Crop Protection Product Formulations Soluble and stable in water Solid or unstable in water Soluble in organic solvent 19601970198019902000 Soluble Liquid Wettable Powder WP in WSB WG SC SC (suitable only if hygroscopically stable) EmulsifiableConcentrate Liquids in WSB Improved EC Oil in water emulsion Micro-emulsion Capsule Suspension

13 1. Nicotinoids History: 1763 for aphids as a ‘tea’ from tobacco From: Nicotiana tabacum, N.rustica Other sources: –Solanaceae: Duboisia hopwoodii, Anthocercis sp, Cyphanthera sp, Crenadium sp –Erythroxylum sp, Asclepius syriaca, Anabsis aphylla Active constituent: nicotine (alkaloid), nornicotine, anabasine Uses: systemic »soft bodied insects eg aphids »almost non-phytotoxic »toxic to humans – only used in confined spaces Action: interfere with nerve impulses Optically active L form most effective

14 -> Neonicotinoids Imidacloprid Type: chloronicotinyl –Readily absorbed by plants Uses: fleas, beetle larvae, termites, many crop pests –Acts quickly on piercing-sucking insects Action: neurotoxic to insects »binds irreversibly to post-synaptic nicotinergic acetylcholine receptors »chlorination inhibits degradation of acetylcholine esterase »toxic to honeybees Thiamethoxam


16 2. Rotenoids From: roots of »Derris eliptica, D.malaccensis (Malay peninsula, Burma, Thailand) »Lonchocarpus utilis (Peru, Brazil) »Tephrosia vogelis (West Africa) History: 1649 to paralyse fish, 1848 against caterpillars Constituents: isoflavenoids - rotenone »Others: eliptone, deguelin, toxicarol Uses: soft bodied insects, red spider, greenfly, caterpillar, wasps Action: contact and stomach poison »on mitochondria / electron transfer balance »cause respiratory depression -> paralysis »low human toxicity »some mammalian toxicity – limits its use Formulation: insoluble, unstable in alkali

17 3. Pyrethrins From: young flower florets of Chrysanthemum cinerariifolium Synonyms: pyrethrum, Dalmatian pyrethrum, Tanacetum cinerariifolium, Pyrethrum cinerariifolium Source: Kenya, Tanzania, Rwanda, Equador Conditions: 1900-2700m altitude, 76-180cm rainfall Market: 1986 13000 tonnes dried flower heads; US$36M Transport: baled, mostly powder / standardised liquid extract

18 Active constituents: mixed esters »pyrethrin I & II, jasmolin I & II, cinerin I & II Action: very rapid paralysis at the nerve ganglia in thoracic region of the insect »if used with another insecticide -> death »not phytotoxic »not toxic to humans Labour intensive picking flowers…. R’ Chrysanthemic acid Pyrethrolone part

19 -> Synthetic pyrethroids Permethrin Formulation: »with dipiperonyl butoxide – enhances activity »poor water solubility – with oils or solvents »not very light stable, store in dark, low temps Uses: foliar for many crop pests, insect repellant »resistance develops quickly Action: neurotoxin, prolongs sodium channel activation »non-toxic to humans »toxic to cats, fish, honeybees


21 Bioallethrin Cypermethrin Fenvalerate Permethrin Non CyanoCyano

22 4. Ryanodine From: South American plant Ryania speciosa Constituent: alkaloid – a complex ester Use: traditionally on poison darts »against the codling moth (apple), European corn borer Action: binds to ryanodine calcium channel receptors in skeletal/heart muscle »low concentrations locks the receptor half open »higher concentrations causes influx of calcium from sarcoplasmic reticulum Biodegradable, deleafs forests

23 5. Quassia Wood (simple) extract of Quassia amara Saponins – good against aphids Use may revive due to aphid resistance 6. Cevadilla (sabadilla) seed From: Schoenocaulon officinale, Mexico to Venezuela Constituents: mixed alkaloids ‘veratrine’ »main ones: cevadine, veratridine Uses: controls thrips and true bugs that attack vegetables »powdered seeds or veratrine preparations used a dust or spray Action: increases sodium permeability of axons

24 7. Tar oils From wood of pine and juniper Used a long time Very phytotoxic »only used on dormant plants ‘winter wash’ »eg fruit trees, rose bushes Acts on most fungal pests as well as insects Cheap and effective 8. Acorus calamus Rhizome and leaf oils Constituents: asarone (β and α), linalool Use: by the Chinese a long time »against diamond-backed moth Action: may have anti-juvenile hormone activity

25 9. Neem From: Azadirachta indica »margosa (seed) oil, leaf extracts Constituents: 25+ active compounds »limonoids (nortriterpinoids) - azadirachtin Use: believed to work against many insects »including borers, leaf beetles, fruit flies Action: »Anti-feedent: suppresses the insect's desire to feed and, therefore, no damage is caused »Repellent: Insects simply stay away from areas sprayed with Neem and, therefore, no damage is caused »Insect Growth regulator: Neem disrupts the insect's delicate hormonal balance so it dies before it molts to the next life stage Formulation: applied as a foliar spray or as a soil drench for systemic control

26 10. Sucrose octanoate esters Sucrocide: found on tobacco leaf hairs Action: dissolves insect exoskeleton Use: aphids, leafhoppers, bugs, caterpillars, mites 11. Other plants Anethum graveolens (dill) Nigella sativa (black cumin) –concentration dependent inhibition of »larvae -> pupae »pupae -> adult –against red wheat flour beetle –by fumigation of essential oil from fruits Pistia stratiotes Cyperus rotandus –please find information! Desmodium caudatum Oregano

27 12. Spinosads (spinosyn A, D) New: chemical class of natural insecticide, novel action From: Saccharapolyspora spinosa, rare actinomycetes or soil fungus – fermentation products Uses: contact and stomach activity, good larvicidal »fruit flies, caterpillars, leafminers, thrips, termites, sawflies, spider mites, leaf beetle larvae »long residual activity Action: disrupts binding of ACh in post-synaptic nicotinic acetylcholine receptors causing overstimulation of the nervous system »low toxicity for mammals »highly toxic for bees »non-phytotoxic for most crops

28 13. Mectins From: –Steptomyces avermitilis – fermentation products –Abamectin »local systemic qualities permitting it to kill mites in leaf’s underside when only upper surface is treated »-> analogs: avermectin, emamectin, milbemectin –Emamectin »contact and stomach insecticide »lepidopterus larvae Use: insecticidal, acaricidal, nematicidal Action: block GABA at the neuromuscular junction »visible activity soon after exposure »death may not occur for several days

29 14. Kaolin Clay From: Kaolinite (China clay) –a mineral clay –Al 2 Si 2 O 5 (OH) 4 Formulation: spray –on fruit, vegetables Action: creates a physical barrier –irritates the mouthparts of chewing insects –prevents oviposition (egg laying) Use: for boring or mining larvae

30 15. Diatomaceous earth Diatomite, Kieselguhr naturally occurring soft chalk-like sedimentary rock –fossilised remains of hard-shelled algae, diatoms –very porous –typically 86% silica, 5% sodium, 3% magnesium, 2% iron Action: physico-sorptive properties –Insects: fine powder absorbs lipids from their cuticle -> dehydration –Gastropods: also works against eg snails/slugs

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