Download - S2 L2 Insecticides - natural
S2 L2 Insecticides - natural
Anna Drew
with slide contribution from Martin Wilks, Syngenta,& Rhonda Hamm
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
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.
Stages of Risk Assessment
Toxicological Hazard Assessment
Identification of intrinsic toxicological properties and assessment of their relevance to humans
World Health Organization (WHO) Classification of Pesticides by Hazard
LD 50 for the rat (mg/kg body weight)
Class Oral Dermal
Solids Liquids Solids Liquids
Ia Extremelyhazardous 5 or less 20 or less 10 or less 40 or less
Ib Highlyhazardous 5 - 50 20 - 200 10 - 100 40 - 400
hazardous 50 - 500 200 - 2000 100 - 1000 400 - 4000
III Slightlyhazardous Over 500 Over 2000 Over 1000 Over 4000
II Moderately
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)
Stages of Risk Assessment
Toxicological Hazard Assessment
Dose-ResponseEvaluation
Determination of quantitative relationships between internal dose and effects for the endpoints of concern
The Dose Response Curve
Stages of Risk Assessment
Toxicological Hazard Assessment
Human ExposureAssessment
Dose-ResponseEvaluation
Assessment of intensity, frequency, duration and routes of human exposure for the purpose of quanti-fication of internal dose
Stages of Risk Assessment
Toxicological Hazard Assessment
Human ExposureAssessment
Risk Characterisation
Dose-ResponseEvaluation
Integration of available information to produce conclusions on the probability of adverse effects
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
Evolution of Crop Protection Product Formulations
Soluble and stable in water
Solid or unstable in water
Soluble in organic solvent
1960 1970 1980 1990 2000
Soluble Liquid
Wettable PowderWettable Powder
WP in WSB
WG
SCSC (suitable only if hygroscopically stable)
EmulsifiableEmulsifiableConcentrateConcentrate
Liquids in WSBLiquids in WSB
Improved ECImproved ECOil in water emulsionOil in water emulsion
Micro-emulsionMicro-emulsionCapsule SuspensionCapsule Suspension
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
-> 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
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
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
• 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
-> 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
CH3
O
CH2CH=CH2CO2
CH3
CH3
CHC
CH3
CH3
HH
Bioallethrin
C CHCl
ClCH3
CH3
CO2CH OCN
Cypermethrin
Cl CHCO2CH
CH(CH3)2
CNO
Fenvalerate
OCH2CO2
CH3
CH3C
Cl
ClCH
Permethrin
Non Cyano Cyano
• 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
• 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
• 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
• 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
• 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
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
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
• 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
• 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