Outlined below are some other organically derived chemicals which are used as insecticides:
Pyrethrin is a natural product extracted from white Chrysanthemum flowers, that have been used as insecticides for over a century. It works against a very wide range of insect pests. The main active principles of Pyrethrum flowers are known as Pyrethrins. Pyrethrin is a fast-acting poison which disrupts the nervous system and causes paralysis of the insect, while at the same time being non-toxic to warm-blooded animals. Pyrethrins are also biodegradable and they break down very quickly in sunlight, moisture and oxygen. Pyrethrins are usually combined with other insecticides like rotenone to ensure their effectiveness. In some people, pyrethrin can cause a skin rash, and breathing the dust can cause headaches and sickness.
Annona trees are grown for fruit in Vietnam. The most useful for making botanical insecticides is custard apple or binh bat (Annona muricata). The botanical insecticide is contained in the unripe fruits, leaves, roots, and especially seeds. It works as a stomach poison, contact poison and repellant. It is said to be effective against leafhoppers and caterpillars.
Neem, derived from the neem tree (Azadiracta indica) of semi-arid tropical regions, contains many active compounds that act as feeding deterrents and as insect growth regulators. The main active ingredient is azadiractin, which is said to be effective on 200 types of insects, mites and nematodes. These include caterpillars, thrips and whiteflies. It has low toxicity to mammals, including people. It is also biodegradable and loses its effectiveness when exposed to direct sunlight.
Nicotine, derived from tobacco, is extremely toxic and fast acting on most animals. The nicotine of half a cigarette, if injected into the blood, is enough to kill a full-grown man. An additional danger of using tobacco leaf extract is that this extract may contain a virus disease called Tobacco Mosaic Virus, or TMV. This virus disease affects a wide range of plants, for example tomato and aubergine. Nicotine kills insects by contact, and if inhaled or eaten. The most common use is to control soft-bodied insects such as aphids, mites, and caterpillars.
Marigolds are often grown in gardens for their attractive flowers, and are even cultivated commercially for use as cut flowers. But marigold can also have a repellant effect on insects and nematodes. Dried marigold when incorporated into soil has been found to improve the overall health of young plants. Fresh marigold tea also repels caterpillars on cabbage, but only for a few hours.
Chilli, or chillipepper. The ripe fruits and seed contain insecticidal compounds and they can control aphids and caterpillars. Highly concentrated chili solution has been known to produce similar results to synthetic insecticides.