This article provides short notes on plant insecticides.
There are some plants which contain chemical substances like alkaloids and inflavonoids which act as insecticides. Alkaloids such as nicotine from tobacco (Nicotinu spp), rotenone from Derris (Derris elliptica) and pyrethrins and cinerins (pyrethroids) from pyrethrum (chrysanthemum cinerariaefolium) are good plant insecticides. Most plant insecticides act as contact poisons being absorbed through the cuticle of the insects.
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The plant Millettia pachycarpa contains two insecticidal compounds known as rotenone and saponine which act as contact and stomach poisons. Rotenone is not harmful to man. The plants belonging to “Solanaceae” or “potato family” are also insecticidal plants.
They contain alkaloids called “Solanaceous alkaloids”. Nicotine, an alkaloid obtained from tobacco acts as a contact insecticide. Nicotine fumigation is responsible for killing of many insect pests. Nicotine sulphate, which is obtained by action of nicotine with sulphuric acid, is used as contact spray.
Nicotine sulphate spray controls flies, aphids, leaf hoppers, thrips and several types of caterpillars. The mixture of nicotine dust, gypsum and nicotine sulphate is very effective insecticide against sweet potato weevil, beet leaf hopper, tobbacco hornworm and onion thrips. Nicotine base is also a promising fumigant.
Plants like castor (Ricinus communis), common basil (ocimum bacilcum), cockroach plant (Haplopnyton cimicidium), Caraway (carum carvi), anise (Opimpinella anisum) and several others have effective insectidal properties against many domestic agricultural pests.
The environment can be saved from agrochemical (insecticides and pesticides) pollution if naturally occurring plant insecticides are used.