S2 L2 Insecticides - natural

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 PESTICIDEREGULATION 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 for the rat (mg/kg body weight) 50 Class Oral Dermal Solids Liquids Solids Liquids Ia Extremely 5 or less 20 or less 10 or less 40 or less hazardous Ib Highly 5 - 50 20 - 200 10 - 100 40 - 400 hazardous II Moderately 50 - 500 200 - 2000 100 - 1000 400 - 4000 hazardous III Slightly Over 500 Over 2000 Over 1000 Over 4000 hazardous

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

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

12. Evolution of Crop Protection Product Formulations Soluble Liquid Soluble and stable in water WP in WSB Wettable Powder Solid or unstable in water WG SC (suitable only if hygroscopically stable) Liquids in WSB Emulsifiable Concentrate Oil in water emulsion Soluble in organic solvent Improved EC Micro-emulsion Capsule Suspension 1960 1970 1980 1990 2000

13. 1. Nicotinoids Optically active L form most effective • 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

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. Chrysanthemic acid • 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…. Pyrethrolone part R’

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. Non Cyano Cyano Permethrin Cypermethrin Bioallethrin Fenvalerate

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 • Al2Si2O5(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