Insecticides A Brief Overview of a Complex Subject

Modes of Entrance into Insect 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 nontarget 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 natural enemies Most insecticides have the potential to affect populations of beneficial insects.

Toxicity to insects natural enemies Highly toxic - Pest populations recover much faster than enemy populations in nature

Toxicity to insects natural enemies Moderately toxic – Pest populations recover somewhat faster than enemy populations in treated environment

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

Toxicity to insects natural enemies Nontoxic – Normal enemy population levels are maintained which quickly attack recovering pest populations

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

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

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

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

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

Resistance/Resurgence Hazard The hazard of populations developing resistance and resurging is evaluated for most insecticides

Resistance/Resurgence Hazard High – Strong potential to develop resistance and resurge

Resistance/Resurgence Hazard Intermediate – Moderate potential to develop resistance in treated environments

Resistance/Resurgence Hazard Low – Minimal potential to develop resistance

Resistance/Resurgence Hazard None – No resistance developed, no resurgence after many treatments

Insecticides

Organochlorines 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

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

Organophosphates 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

Organophosphates 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)

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

Carbamates 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

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

Botanicals 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)

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

Botanicals Pyrethrins Retenone Ryaia

Botanicals Pyrethrins Very toxic to cooled blooded animals, some peoples and cats. Very effective on most insects. it rapidly breaks down in sunlight, air and water.

Botanicals Retenone Derived from the roots of over 68 plant species and is very toxic to fish, pigs, and cool blooded animals Used to control leaf eating caterpillars and beetles Direct contact may cause skin and mucus membranes irritation.

Botanicals Ryaia Botanical insecticides made from the ground stem of Ryana speciosa Is highly toxic to the fruit moths, and citrus thrips

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.

Nicotine 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 oils Some plants also produce essential oils in specialized gland cells:- Peppermint oil( (زيت روح النعناعcontrol of household pests such as cockroaches and ants. Clove oil((كبش قرنفلinhibit soil born fungal disease. Citrus oil control of flea, aphid and mites Lavender oil insect repellent. Thyme oil Rosemary oil Cedar oil--

Microbial 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 Pathogens Bacillus thuringiensisBacillus Sphaericus Baculovirus

Repellants 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

Repellants Repellent for foliage feeders (مواد طاردة للحشرات التي تتغذى على الاوراق النباتية) Such as:- bordeaux mixture (copper sulfate, hydrate lime, water) Repelles of beetles and grasshoppers Copper ions affect enzymes in the fungal spores in such a way as to prevent germination.

Repellants Repellents for crawling insect المواد الطاردة للحشرات الزاحفة Such as:- Cresol ( organic compound, used as disinfectants) Trichlorobenzene (effect for along time, repelled white ants) Repellents to fabric eating insects المواد الطاردة للحشرات التي تتغذى على المواد المصنعة

Repellants repellents to blood sucking insects Such 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 الطاردة 1- ان لاتسبب حساسية لجلد الانسان و الحيوان 2- الا ينتج عن استعمالها رائحة غير مقبولة و ان لا يكون لها تاثير على الملابس 3- ان تعطي حماية لمدة طويلة بتركيزات منخفضة 4- ان تكون رخيصة الثمن و يمكن الحصول عليها بسهولة 5- الا يكون لها تأثير سام على الانسان و الحيوان 6- ان يبقى مفعولها لمدة طويلة 7- يجب ان يكون لها تاثير طارد لانواع عديدة من الحشرات 8-يجب ان لا يفقد مفعولها بسرعة بواسطة عرق الانسان

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

Fumigants Methyl bromide Dichloropropene Chloropicrin Metam-sodium

Transgenic Crops with Insecticidal 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 species Behavioral chemicals = semiochemicals Sex Pheromones Are released by either one( mainly the female) or both genders for the purpose of mate attraction Aggregation pheromones Function 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 pheromones Are 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 الافات الى مصائد تحتوي على مواد سامة.