Insecticide

Étymologiquement, the insecticidal S are active substances or preparations having the property to kill the Insecte S, their larvae and/or their eggs. They belong to the family of the Pesticide S, included to them-even in the family of the Biocide S, both regulated in Europe by specific directives.
Le generic term insecticidal also included pesticides intended to fight against Arthropode S which are not insects (ex: Acarien S such as Araignée S or Tique S) thus sometimes that the repulsive ones).

One distinguishes from the products acting by contact, the products “systemic” , and from the products to intermediate mode, known as “ translaminaires ”.

Chemical families

They are related to the modes of action of insecticides, founded for example on the Neurotoxicité of certain molecules, or on their impact on cellular breathing, the formation of the chitinous cuticule , or the disturbance of the moults.

They are mainly the

  • Organophosphoré S,
  • Carbamate S,
  • Pyréthrinoïdes of synthesis,
  • Organochloré S
  • Benzoyl urea S.

The organochlorinated ones (organohalogen)

Very much used of 1940 to 1970, they are in very clear regression.
Ce term included not systematically any insecticide comprising in its Formula One a chlorine atom.

They are insecticides of contact: none needs to be conveyed by the sap in the plants to act on the insects which eat them.

The organochlorinated ones are poisons neurotropes which deteriorate the operation of the channels sodium essential to the transmission of the nerve impulse. Their spectrum of action is broad.
DDT, for example, acts on the insect by contact and ingestion, inducing a tremor generalized (driving incoordination) then a paralysis which puts sometimes 24:00 to settle.

The acute toxicity of organochlorinated towards the man is relatively low, under the normal conditions of use, but they are very stable and bioaccumulable substances, giving biotransformation and breakdown products (Métabolite S) even more stable, not very water soluble, with weak vapor tension, from where problems of accumulation in the organizations and the ecosystems with via the food chains. Some can persist very a long time in the vegetable grounds, fabrics and greases, this why they were interdict in good number of countries.

In addition to their excessive remanence, their use was slowed down by phenomena of resistance appeared in particular at the Dipterous ones (case of aldrin), of which at some Moustique S.

Examples:

    • group of the DDT: DDD, DDT, Perthane, Métoxychlore
    • group of the HCH: Lindane
    • group of the chlordane: Chlordane, Heptachlore, Aldrin, Dieldrin, Endrin, Chlordécone, Perchlordécone, Diénochlore.
    • derived from the spirits of turpentine: Endosulfan, Toxaphène, Polychlorocamphène
    • various: Dicofol, Chlorfénétol, Mirex, BHC, Pentachlorophénol, Chlorbenside.

Organophosphorés

The first marketing (Parathion) date of 1944. They are currently the most varied insecticides market. These products hardly have common points between them, if it is not their origin, a certain liposolubility and their mode of action on the nervous system. They are inhibiters of the cholinestérase, which is blocked in an inactive form: the Acétylcholine accumulates on the level of the Synapse, preventing the transmission of the nerve impulse and resulting in the death of the insect. This mode of action explains their high toxicity with respect to the man and of the warm-blooded animals.

The majority of organophosphorés penetrate more or less in fabric of the plants, being semi systemic, or are transported by the vascular system of the plant: they are then systemic.

They are located contrary to the organochlorinated ones, with a high acute toxicity but a weak remanence. Their weak remanence often requires the repetition of the treatments to ensure a long protection. They penetrate easily in the organization of the insects by their high liposolubility. Some are specifically Acaricide S.

One distinguishes:

    • Organophosphorés aliphatic: Acéphate, Déméton, Dichlorvos, Dicrotophos, Diméthoate, éthion, Formothion, Malathion, Mévinphos, Monocrotophos, Naled, Ométhoate, Phorate, Phosphamidon, Trichlorfon
They are generally highly toxic and not very stable. They are more stable than the preceding group (better remanence).
    • Organophosphorés with heterocycle: Chlorpyrifos, Diazinon, étrimfos, Isoxation, Quinalphos, Méthidation, Phosmet
Products resulting from these 3 groups are gathered below according to their mode of action:
    • Produced contact: Bromophos, Diazinon, Fénitrothion, Malathion, Dichlorvos, Fonofos, Parathion, Phosmet, Profénofos, Téméphos, Hepténophos, Mevinphos, Trichlorfon, Phosalone
    • Produced systemic: Diméthoate, Formothion, Isofenphos, Triazophos, Monocrotophos, Ométhoate, Phosphamidon, Thiométon, Vamidothion…

Carbamates

This vast group gathers the derivatives of the carbamic acid, also including/understanding a great number of fungicides and weedkillers.

They act like organophosphorés; by inhibiting the cholinestérase. Some have specific actions (Aphicide, Molluscicide). The Propoxur, Bendiocarbe and Dioxacarbe are used in paludic fight for their great remanence.

They generally act by contact although some have a systemic action (aldicarbe, benfuracarbeé). Their remanence is generally weak.

One distinguishes:

  • the methyl carbamates having a cyclic structure phényl: Aminocarbe, BPMC, Carbaryl, Isocarbe, isoprocarbe (MICP), Methiocarbe, Metolcarbe (MTMC), Mexacarbe, Promecarbe, Propoxur.
  • methyl and dimethyl carbamates having a heterocyclic structure: Bendiocarbe, Carbofuran, Dimetilan, Dioxacarbe, Pirimicarbe.
  • the methyl carbamates with alliphatic chain: Aldicarbe, Methomyl, Oxamyl, Thiodicarbe.
    • Examples: Benfuracarbe, Diallate, Dimétan, éthiophencarbe, Fenoxycarbe, Formetanate, Formetanate hydrochloride, Mercaptodimethur, Thiofanoxe

The pyrethrinoid ones of synthesis

Insecticides known as “of third generation”, they are copied from the natural pyrèthres, while seeking to increase their toxicity and their photostability.
Dotés of a toxicity considerable and acting by contact, they kill almost instantaneously the insects by neurotoxic shock effect, making it possible to use them with very reduced amounts (10 to 40 G of active matter per ha).
Comme the organochlorinated ones, they kill the insect by blocking the operation of the channels sodiums essential to the transmission of the nerve impulse. Considered not very toxic for the man, one allots to them the safety coefficient (report/ratio of toxicities for the insects and the mammals) highest among chemical insecticides. Very biodegradable, they do not persist in the edaphic medium, but they are very toxic for certain watery organizations (fish) like for the auxiliaries of the agriculture (of which bees). They have various properties.

A given molecule present of many isomers at the degrees of activities varied. The industrial synthesis seeks to produce only the most active isomer of the molecule.

The sulfonic ones and sulphonates

They have a connection sulfur in common. Slightly toxic, they have acaricide properties (against eggs and larvae), but they are practically ineffective with respect to the insects. *Exemples: Tétrasul, Tétradifon, Propargite.

Formamidines

They are acaricide insecticides characterized by the presence of a structure - N=CH-N. They kill eggs and the young larval stages. They are effective against the insects having developed a resistance to organophosphorés or the organochlorinated ones.
    • Examples: Amitraze, Chlordimeform, Formetanate.

Benzoylurées (disturbing of moults)

It is a group of insecticides discovered in 1972, the diflubenzuron being the first marketed active matter. It is characterized by its mode of action which disturbs the formation of the chitin which is not any more in fibrillary form of the larvae of insects. Chitin synthétase is the active site. The insects die at the time of the following moult. They are slightly toxic for the man. The time of action is from 2 to 7 days. Their half-life is 2 weeks.
    • Examples: Diflubenzuron, Teflubenzuron, Hexflumuron, Lufénuron, Triflunuron.

Other families

Carbinols : They all are practically of the specific Acaricide S. Close relations of the group of DDT, they include/understand chlorinated and brominated derivatives. *Exemples: Dicofol, Chlorobenzilate, Chloropropylate, Chlorfénétol, Bromopropylate.

Insecticides of vegetable origin

In Europe, they experienced a significant development between the two wars, before being eclipsed by insecticides of synthesis. Cultures with large scales of plants with insecticidal property were carried out in the Fifties. These insecticides are extracted from various plants by maceration, infusion or decoction. Here are some examples:

derivatives of the Pyrèthre

The Made up ones of the kind Chrysanthemium accumulate in their flowerheads of the insecticidal substances, the Pyréthrine S. Chrysanthemuim cinerariaefolium is the species most employed. The flowers, recalling by their form the daisies, are crushed and dried. The powder obtained is diluted with the 1/10ème in water. The effect is increased by the addition of additives, such as the piperonyl butoxide. Not very toxic, the Pyréthrine S is very quickly degraded in nature. They are active against many insects with a shock effect.

the Roténone S

They are extracted from roots, sheets or seeds of Légumineuse S ( Derris spp in Southeast Asia and Lonchocarpus spp in South America). They are very toxic for the Poisson and certain insects which they paralyze (inhibition of the complex mitochondrial I, i.e. respiratory chain on cellular scale) but are considered inoffensive for the Abeilles and little poisons for the warm-blooded animals. Their residual effects are considered weak. It is an insecticide of contact, used against the sucker and crushing insects (Puceron S, Teigne S, flies of the fruits, Altise S, Noctuelle S).

Preparation: roots of Derris elliptica 2,6 cm in diameter are washed then crushed with a little water and soap (1 share of soap, 4 shares of roots and 225 of water). The solution obtained by filtering is used immediately. Caution! The Roténone S cause by contact of severe lesions of the genital areas.

the Nicotine

Extracted on the level from the sheets and the stems tobacco, Nicotiana tabacum ( Solanaceae ). This alkaloid acts by inhalation, ingestion and contact. The Nicotine has acaricide properties, insecticide and fungicide. Nicotine is degraded in 3-4 days. It is a very toxic substance for the man, the mammals and fish. Its DLL 50 is of 50 mg/kg. It can be inhaled and absorptive directly through the Peau: it is thus necessary to avoid any contact during its handling. The treatment is more effective if it is held with high temperature (>30°C). One should not consume the cultures treated before a 4 days deadline.

Preparation: the pulp prepares by sprinkling 1 kg of stems and sheets with 15 water L plus a soap handle (surface-active agent). After 24:00, this mixture is filtered and ready with employment.

the Azadirachtine, azadirine and other alkaloids (neem)

Extracted from a tree ( Azadirachta indica : Margousier) of the family of the Meliaceae , the azadirachtine has properties insecticide and repulsive on more than 200 species of insects of 6 different orders and has fungicidal properties. She acts by contact and ingestion. The product being degraded under the action of the light, it is advised to treat in end-of-day. The product is effective against the tinea of the crucifères, the ladybird of melon and certain cicadelles.

The neem extracts from seeds allows, a concentration of 3-5 ppm, to protect the food products stored over one 6 months period.

Preparation: the seeds are removed from pulp and the cores are dried in the shade. Once quite dry, they can be preserved several months. Then the seeds are reduced powders some and put to soak in water (25 to 50 G of seeds per liter) during one night. The solution obtained starting from the sheets and seeds is used in pulverization against the caterpillars défoliatrices of the market gardenings.

The sheets and the flowers are placed under the bed linen against the Poux and the Puces. This product is without effect on the man and the mammals and disturbs only moderately auxiliary fauna. The neem is used in coating with the seeds. A factory of extraction of this substance exists in India (1995) with a capacity for treatment of 20 T per day.

With Madagascar, the plant specie used is Melia azedarach ( Meliaceae ).

the Quassine

This product is extracted from a tree from 4 to 6 m in height, the Quassia will amara , of the family of the Simarubaceae with the Brésil and in Central America, as well as another tree reaching 12 m, Picraena excelsa . This substance is present primarily in wood. The quassine is practically inoffensive for the pets and the man. It does not affect the useful insects such as the Abeilles and the Coccinelles. Water soluble, it is a systemic product used primarily against the sucker insects (plant louses).

Preparation: one makes macerate 2 to 3 days 1 kg of chips in 6 liters of water. The water of steeping is used in pulverization added with white soap 1%. The quassine has an insecticidal action and nématicide.

The long persistence of the very bitter taste of the product prevents from directly applying the product to the sheets or fruits consumable.

the Ryanoline

This substance is extracted from Ryania speciosa , from the family of the Flacourtiaceae and meets in South America. One uses the stems, the roots and the sawdust of trunk. The product acts by contact and the effect is slow but very powerful, the insects ceasing nourishing themselves, moving and reproducing. It is a selective insecticide by ingestion. The Ryania is not very toxic for the vertebrate ones and the effect hard with field 5 to 9 days. One obtains good performances towards the larvae of Lépidoptères.

Preparation: the roots the sheets or the stems are dried then ground finely. 30 to 40 G of powder are mixed with 7 to 8 liters of water. then the liquid obtained by filtering is pulverized, all the 10 to 14 days in arboriculture.

the Aconitine

This substance comes from various species of Aconitum ( A. fischeri, A. kuznezoffi, A. autumnale , A. napelluse ). These plants contain aconitine and others very toxic Alcaloïde S for the mammals, the birds and the invertebrates. DLL 50 of the Aconitine is close to 1. In China, these plants are cultivated for the treatment of seeds.

The géraniol

The Géraniol is obtained by split distillation of natural extracts of Cympobogon winterianus Jowitt. It was shown that the géraniol in aqueous solution had a double action on the insects and all the stages of the metamorphosis, by smothering and dehydration of the insect, eggs and the larvae. It is even one of the best larvicides of the market.

See too

Insecticide|Insecticide

Random links:Airport of Stockholm-Arlanda | Jacques Dutronc (1972) | Balajade (brook) | Airco DH.6 | Cheerfulnesses of the squadron | Théorie_des_modèles