Plants have undergone an evolutionary period of 400 million years, during which time mechanisms such as the production of repellents and insecticides have evolved to protect themselves against insects that attack them. Plant species contain natural insecticides. Some of these substances have been used by humans since ancient times, but many of these compounds cannot be extracted.
Essential oils and plant extracts:
In plants, certain substances are biosynthesized, called secondary metabolites. Secondary metabolites play an important role in the defense of plants against herbivorous insects. Compounds such as alcohols, terpenes, and cyclic compounds are released by plants. These volatile substances can repel pests. Vegetarians, poisoning or attracting parasitoids and predators in response to damage caused by pest feeding.
They prepare essential oils and extracts from plants. Plant essential oils are a group of secondary metabolites in plants that are volatile and sometimes fragrant. The constituents of plant essential oils are terpenoids with a chain or ring structure that are composed of isoprene units (C5H8). Hydrocarbons, alcohols, ketones and other derivatives are also present in essential oils.
There is a difference between essential oil and plant extract. Essential oils are oily, volatile and immiscible with water and have a specific gravity of less than one. Also, their smell and taste are special. If plant extract is a solution that contains all the substances in the plant. These include essential oils, tannins and alkaloids. The plant extract also affects arthropods through contact and respiration.
Nicotine and similar compounds:
In the past, tobacco juice was used to control sucking insects in the garden. Later, it was discovered that the active ingredient in tobacco juice is an alkaloid called nicotine. It is a colorless substance that oxidizes in the presence of air and turns brown. Nicotine is effective on vertebrates because it mimics the molecular state of acetylcholine and occupies the receptors of this neural interface at synapses, causing convulsive contractions and eventually death. The toxic effects of this compound appear quickly and lead to death within 5 to 30 minutes. Nicotine is absorbed through the tongue, stomach wall and skin. Used. Carnes period of this combination is 7 days.
This group of synthetic insecticides are called nicotinoids and conventional chloronicotinyl compounds that are similar to nicotine.
This insecticide was discovered in 1985 and introduced in 1990. This insecticide is especially effective in contact and digestive form for sucking insects and is absorbed through the roots, leaves and trunk injection into the plant stem.
This compound entered the market in 1998. This compound is rapidly absorbed by the plant and moves acroptally in the woody vessel. Thiamtoxam is not toxic in itself and is a precursor to clotianidine. More is turning.
Pyrethrins are compounds found in the extract of plant flowers called pyrethrum cinerariaefolium. The oldest dried flower contains 1% of the oldest, which is extracted by solvents such as odorless oil and ethylene dichloride.
In general, the compounds extracted from this flower all have insecticidal properties and are called the oldest compounds. The oldest is important because insects such as mosquitoes and flies come into contact with it due to the impact effect after a few seconds. They fall to the ground, and on the other hand, these compounds are much less toxic to mammals, but the main problem with this compound on the farm is that it is very unstable in the presence of air and light.
The rapid and impact effect of elders on flying insects indicates that this compound is effective on the nervous system of insects. After contact with these substances, the insects show symptoms similar to the effect of DDT in terms of behavior and physiology. .
Following the research on the chemical structure of the oldest natural, it was possible to synthesize similar compounds, so that these compounds, having the same or superior insecticidal properties as natural pyrotenoids, also had the advantage that against factors such as air and light from They had good stability.
From this group of insecticides, we can mention: Permethrin-Delta Metrin-Fan Valerite-Fan Propatrin-Cypermethrin-Lambda Sai Halotrin.
Neem plant products
Compounds of neem tree, which is a kind of bitter olive with the scientific name of Azadirachta indica Juss. And is also grown in the south of Iran. It is related to it and is extracted from neem seed kernels. Azadirachtin is structurally similar to peeling hormone and inhibits the activity of this hormone in the body of the insect. Also, this compound has an appetizing and sterilizing effect and affects the insect by reducing regeneration and metamorphosis.