Insecticides A Brief Overview of a Complex Subject

InsecticidesInsecticides

A Brief Overview of a Complex Subject

Modes of Entrance into Modes of Entrance into InsectInsect

Contact - dermal – through the skin

Stomach - oral – through the mouth

Respiration - inhalation through the nose or gills

Systemic - combination of above

Toxicity to humans or Toxicity to humans or nontarget organismsnontarget organisms

Most insecticides have the capacity to affect non-target organisms

Same as previously discussed Highly toxic – LD50 0 – 50 mg/kg

Moderately toxic - LD50 50 – 500 mg/kg

Low toxicity - LD50 500 – 5,000 mg/kg

Nontoxic - LD50 <5,000 mg/kg

Toxicity to insects Toxicity to insects natural enemiesnatural enemies

Most insecticides have the potential to affect populations of beneficial insects.


Highly toxic - Pest populations recover much faster than enemy populations in nature


Moderately toxic – Pest populations recover somewhat faster than enemy populations in treated environment


Low toxicity – Natural enemies are maintained to a degree & quickly attack recovering pest populations


Nontoxic – Normal enemy population levels are maintained which quickly attack recovering pest populations

Environmental hazardEnvironmental hazard

Environmental hazard of insecticides is generally evaluated as a function of persistence often compared to effectiveness


High – Environmental persistence far greater than period of effectiveness (> 5 months and often > a year)


Intermediate – Persists beyond effectiveness (3-5 month half-life)


Low – Persists about the period of effectiveness (up to about 3 months) and then degrades completely over several months


Very low – Persists for short periods (>45 days) and degrades completely

Resistance/Resurgence Resistance/Resurgence HazardHazard

The hazard of populations developing resistance and resurging is evaluated for most insecticides


High – Strong potential to develop resistance and resurge


Intermediate – Moderate potential to develop resistance in treated environments


Low – Minimal potential to develop resistance


None – No resistance developed, no resurgence after many treatments

InsecticidesInsecticides

OrganochlorinesOrganochlorines

•Also called the chlorinated hydrocarbon insecticides•Characterized by containing chlorine and carbon atoms•Powerful nerve poisons•Most affect a broad spectrum of non-target organisms along with the target pests•Long persistence and residual activity

OrganochlorinesOrganochlorines

Several were used in forestry DDT Lindane Dicofol (Kelthane) Endosulfan (Thiodan)

OrganophosphatesOrganophosphates

•Also known as the Ops• Characterized by containing carbon and phosphorus atoms• Generally only short term persistence and limited residual activity• Unfortunately, often have broad spectrum activity against beneficial insects

OrganophosphatesOrganophosphates

Several used in forestry or applied to forests for public health purposes

Malthion (Malathion and Cythion) Acephate (Orthene) Methyl parathion (Methyl parathion) Diazinon (Diazinon and Spectracide) Chlorpyrifos (Dursban and Lorsban) Azinphos methyl (Guthion)

OrganosulfursOrganosulfurs

•Small group of sulfur containing insecticides•Low insect toxicity, but with good miticidal characteristics

CarbamatesCarbamates

•Insecticides which are derivatives of carbamic acid•Non-target toxicity is chemical specific, ranging from low to very high• Generally only short term persistence and limited residual activity• Often with broad spectrum activity against beneficial insects

CarbamatesCarbamates

Very few used in forestry Carbaryl (Sevin) Aldicarb (Temik) Methomyl (Lannate)

BotanicalsBotanicals

•Chemicals extracted or derived from plants •May be present and subsequently extracted from the plant material (a constitutive chemical), or• May be activated in the plant as a response to insect activity (inducible chemicals)


•Some are chemically modified after extraction to enhance their insecticidal properties


Pyrethrins Retenone Ryaia


Pyrethrins

1. Very toxic to cooled blooded animals, some peoples and cats.

2. Very effective on most insects.3. it rapidly breaks down in

sunlight, air and water.


Retenone1. Derived from the roots of over 68

plant species and is very toxic to fish, pigs, and cool blooded animals

2. Used to control leaf eating caterpillars and beetles

3. Direct contact may cause skin and mucus membranes irritation.


Ryaia1. Botanical insecticides made from

the ground stem of Ryana speciosa

2. Is highly toxic to the fruit moths, and citrus thrips

Nicotine Nicotine

• Nicotine a plant defense alkaloid • Nicotine is a fast acting contact killer

for soft bodies but does not kill most chewing insects.

• Concentrate is very poisons if inhaled.• Highly toxic to warm blooded animals.• Pale yellow to dark brown liquid.

NicotineNicotine

• The effectiveness is similar that of organophosphorous compounds

• Nicotine inhibits the function of acetylcholine receptors located at the neuromuscular junctions.

• Nicotine is highly lipophilic and can pass through dermal tissues as well as the blood brain barrier.

Essential oilsEssential oils

Some plants also produce essential oils in specialized gland cells:-

1. Peppermint oil( (زيت روح النعناعcontrol of household pests such as cockroaches and ants.

2. Clove oil((كبش قرنفلinhibit soil born fungal disease.

3. Citrus oil control of flea, aphid and mites4. Lavender oil insect repellent.5. Thyme oil6. Rosemary oil 7. Cedar oil--

Microbial PathogensMicrobial Pathogens

•Fungi, bacteria, viruses, etc. which can be used to cause disease in an insect population•Relatively narrow spectrum of activity, not broad spectrum insecticides•Several have been genetically engineered to kill target insects more rapidly

Microbial PathogensMicrobial Pathogens

Bacillus thuringiensisBacillus SphaericusBaculovirus

RepellantsRepellants

•Large group of unrelated chemicals•Many experimental chemicals – but to the present no truly effective forest protectant chemical•Mostly have found use for people or livestock protection


Repellent for foliage feeders (مواد طاردة للحشرات التي تتغذى على االوراق النباتية)Such as:-• bordeaux mixture (copper sulfate, hydrate lime, water)Repelles of beetles and grasshoppersCopper ions affect enzymes in the fungal spores

in such a way as to prevent germination.


Repellents for crawling insectالمواد الطاردة للحشرات الزاحفة Such as:- • Cresol ( organic compound, used as

disinfectants)• Trichlorobenzene (effect for along time, repelled

white ants)

Repellents to fabric eating insectsالمواد الطاردة للحشرات التي تتغذى على المواد

المصنعة

nfayyad


repellents to blood sucking insectsSuch as:-• Dimethyl phthalate ( anopheles, aedes,

culex)• 2-Ethyl-1.3- hexonediol ( house fly,

mosquito, flea)• DEET( applied to skin and cloths and is used

to repel mosquitoes)• Citronella oil ( personal insect repellents

such as mosquito)• Oil of lemon Eucalyptus ( active against

mosquito)

الشروط الواجب توافرها في المواد الطاردةالشروط الواجب توافرها في المواد الطاردة

ان التسبب حساسية لجلد االنسان و الحيوان -1اال ينتج عن استعمالها رائحة غير مقبولة و ان ال يكون لها -2

تاثير على المالبسان تعطي حماية لمدة طويلة بتركيزات منخفضة -3

ان تكون رخيصة الثمن و يمكن الحصول عليها بسهولة -4اال يكون لها تأثير سام على االنسان و الحيوان -5

ان يبقى مفعولها لمدة طويلة -6يجب ان يكون لها تاثير طارد النواع عديدة من الحشرات -7 يجب ان ال يفقد مفعولها بسرعة بواسطة عرق االنسان-8

FumigantsFumigants

•Fumigants generally contain a halogen (chlorine, bromine, fluorine, etc.) in their molecules•Small molecules which vaporize at relatively low temperatures

FumigantsFumigants

Methyl bromide Dichloropropene Chloropicrin Metam-sodium

Transgenic Crops with Transgenic Crops with Insecticidal PropertiesInsecticidal Properties

Plants genetically engineered to enhance insecticidal properties

Pheromones

Pheromones(chemical used for communication within species)

Chemical signal that triggers a natural response in another member of the same speciesBehavioral chemicals = semiochemicals

• Sex PheromonesAre released by either one( mainly the female) or both genders

for the purpose of mate attraction• Aggregation pheromonesFunction in defense against predator, mate selection

and overcoming host resistance by mass attack• Alarm phrmones Some species release a volatile substance when

attacked by predator that can trigger flight ( in aphid)

Pheromones

• Trail pheromonesAre common in social, for example ants make their

paths with these pheromones which are non volatile hydrocarbones

• Releaser pheromones Are powerfull attraction molecules that some

insects may use to attract males from a distance of two miles or more

Pheromones

بدا المختصون في استخدام الفرمونات و خاصة الجنسية منها للحد من اضرار الحشرات حيث

تم انتاج مركبات شبيهة بالفرمونات و قد نجحت بعض التطبيقات الحقلية باستخدام

الفرمونات المصنعة للتقليل من اضرار بعض الحشرات كدودة جوز القطن القرنفلية و يمكن

استخدام الفرمونات المصنعة او الطبية في مقاومة الحشرات بتوجيه افراد االفات الى

.مصائد تحتوي على مواد سامة

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Insecticides A Brief Overview of a Complex Subject