Neem Oil: Organic Pest Control (Part One)
By Cosmo MacKenzie • 2 years Ago
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By Cosmo MacKenzie • 2 years Ago
Also known as Indian Lilac, Neem has as many names as there are dialects stretching from Nigeria in West Africa to Thailand in South-east Asia. Muarubaini is one such name, which means ‘the tree of the forty’ in Swahili; so named because it is said to treat forty different diseases. Ancient Ayurvedic texts indicate that Neem has been used for centuries to treat ailments as various as leprosy, malaria, tuberculosis and even good old acne. Western science has taken an embarrassingly long time to catch up with the local ‘witch doctors’, but thankfully for us neem products are now widely used and internationally recognised for their many beneficial qualities; and there are a lot of them.
Noted for its reliance in periods of drought, the neem tree grows quickly and to heights of fifteen to twenty metres, bearing small white fragrant flowers. Neem oil is pressed from the seeds and fruit of this glorious, fast growing evergreen. Neem oil has so many applications that you could write a whole book about it. In fact a number of people have (see your local stockist for details). For the purposes of this article, we’ll have a look at some of the qualities that underpin neem oil’s success and at its application in the wonderful world of horticulture.
“Neem oil doesn’t act like napalm. Just because you don’t see a neat little pile of dead bugs, doesn’t mean it isn’t doing its job.”
The fatty acids which constitute the composition of Neem oil are at the heart of its success.
Omega-3, omega-6 and omega-9 help to regulate blood pressure, reduce the risk of cardiovascular diseases and help the body fight cancer and degenerative diseases like Alzheimer’s.
Palmitic acid is thought to help regulate insulin levels and is used in the treatment of schizophrenia.
Stearic acid is used in all sorts of things from soap to playing cards and even fireworks.
Palmitoleic acid may help to fight obesity, and is possibly partially responsible for body odour (well, seven out of eight isn’t bad).
Unlike some of its chemical counterparts, neem oil doesn’t act like napalm; killing everything in sight with immediate effect. Just because you don’t see a neat little pile of dead bugs, doesn’t mean it isn’t doing its job. Neem oil has an altogether more insidious effect on the little buggers; not unlike having your mother in law move in with you. Neem oil acts as a larvicide, curtailing the invading insect population’s ability to perpetuate.
“…by inhibiting the insects’ ability to eat, grow, mate and lay eggs, neem oil breaks the cycle of propagation in the community of unwelcome guests, foolhardy enough to squat on your crop.”
For the gardeners among us, neem oil’s most attractive application is as a biopesticide. Where neem oil differs from most conventional pesticides is that it acts on an insect’s hormonal system as opposed to its nervous or digestive system. The most notable advantage to this is that it doesn’t lead to the development of resistance in the future.
As an insect larva munches its way through your crop, it grows. As it gains mass it becomes necessary for the lava to shed its skin, whereupon the process starts anew. This process of moulting, called ecdysis, is governed by the enzyme ecdysone. Azadirachtin in neem oil acts to suppress ecdysone, the result being an inability in the larva to shed its skin and accordingly an inability to grow. Ultimately this leads to the larva’s death. Those larvae who manage to escape these effects, usually as a result of too low a concentration of azadirachtin in the dose, die in the pulpal stage. Those larvae that experience an even lower dose of azadirachtin emerge as malformed adults who are completely sterile and unable to reproduce. That’ll teach them.
Neem oil also acts as an oviposition deterrent, which means it prevents females from laying eggs.
“As if yacking its guts up wasn’t enough, its ability to swallow is also blocked. It won’t be going back for seconds any time soon.”
Neem oil’s most endearing quality to gardeners is as a feeding deterrent. When an insect feeds on a leaf treated with neem oil, azadirachtin, salanin and melandriol in the treated leaf produce an anti-peristaltic wave in the alimentary canal of the insect; inducing the greedy little blighter to vomit. As if yacking its guts up wasn’t enough, its ability to swallow is also blocked. It won’t be going back for seconds any time soon.
Thus, by inhibiting the insects’ ability to eat, grow, mate and lay eggs, neem oil breaks the cycle of propagation in the community of unwelcome guests, foolhardy enough to squat on your crop. It is claimed that even the slightest hint of the presence of neem oil on your crop is enough to deter leaf eating insects; and who could blame them for that?
As an added bonus, neem oil’s efficacy in such small doses means its use is notably benign to helpful insects further up the food chain, like spiders, bees and butterflies that help to germinate crops. Since humans consume neem oil in much greater quantities it is obviously equally safe for those of us at the top of the food chain and our lesser mammalian compatriots.
This article was originally published in Issue 001 of HYDROMAG (September – October 2012).
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