There is no doubt botanical insecticides are an interesting alternative to insect pest control.
The first botanical insecticide, used as such, dates back to the XVII Century when it was shown that nicotine could kill plum beetles. More recently other plants like quasia (Quaisa amara, Simaroubaceae), neem or Margosa (A. indica) which besides giving excellent results for insect control are also a source of compounds used against cancer. Is not uncommon to hear of home recipes mentioning the use of fennel (Foniculum vulgare), rue (Ruta graveolens) and eucalyptus (Eucaliptus globolus) among other aromatic plants to repel insects.
After the Second World War the few plant and plant extracts that had shown promising effects, and were of widespread use, were replaced by synthetic insecticides. When synthetic insecticides appeared in the 1940’s some people thought that botanical insecticides would disappear forever but problems like environmental contamination, residues in food and feed and pest resistance brought them back to the fore.
Now is our duty to implement the use of natural repellents in our crops!
Description of Some Natural Compounds:Rotenone- Rotenone is a flavonoid extracted from the roots of two plants:
Derris spp. (Fabaceae) and
Lonchocarpus spp. (Fabaceae). Derris spp. is a native to Eastern tropics, while Lonchocarpus spp. is native to western hemisphere.
Sabadilla- This is a compound that can be obtained from seeds of a plant of South American origin known as
Schoenocaulon officinale (Liliaceae). The ground seeds are one of the plant insecticides with the lowest mammal toxicity but that is not the case with their isolated alkaloids which are both highly toxic and skin irritants.
Nicotine - Nicotine is an alkaloid obtained from some plants in the Solanaceae family, particularly
Nicotiana tabacum. This compound is not found free in the plant but in the form of maleates and citrates. Nicotine is essentially a non-persistent contact insecticide.
Ryania- This compound is obtained from the roots and stems of a plant native to South America known as
Ryania speciosa (Flacourtiaceae)
Azadiractin- This compound is a tetraterpenoid characteristic of the Meliaceae family but particularly from the
Neem tree (A. indica), indigenous to India. The compound is found in bark, leaves and fruits of the tree but seeds have the highest concentration.
Pyrethrins- Pyrethrins, which are esters with insecticidal properties, are obtained from pyrethrum (
T. cinerariaefolium) flowers. The compounds obtained from this plant which have known insecticidal activity are six esters formed by the combination of the acids chrysanthemic and pyrethric and the alcohols piretrolone, cinerolone and jasmolone.
The use of extracts and powdered plant parts as insecticides goes back at least as far as the Roman Empire. For instance, there are reports that in 400 B.C. the delousing procedure for children was with a powder obtained from the dry flowers of a plant known as pyrethrum (Tanacetum cinerariaefolium).
Although our allies, it would be a big mistake to consider products of plant origin, and this includes botanical insecticides, harmless merely because they are natural...
As Paracelsus wrote in 1564 :
“
the difference between something that kills and something that cures is the rate.” 
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Topic: Botanical Insecticides (Read 3202 times)