Neem Oil

David Taylor · Posted: Mon May 11, 2009 1:30 pm Post subject: Neem Oil

Recently I broke down and tried BTK and Neem oil. In the past I've relied on home-made insect repellants which, for the most part, have failed me. I've now tried Neem oil on acorn squash, cucumbers and zukes that would be covered in mold by now, and it seems to work like magic. All three are doing just wonderfully. It's required very little of either of these store-bought repellants, and the beneficials seem unaffected. I tried BTK on corn last year, sprayed only twice, and the corn worms were gone, as if I'd broken a cycle.

BTK I get, but what is Neem Oil, how does it work, and why is it considered organic?

mostaza · Posted: Thu Jun 04, 2009 3:43 am Post subject: neem

I have HEARD(and nothing more) that all plants and beneficials and even human skin benefit from neem oil. I even know people who use it prior to any type of problems simply to improve the health of plants.
Based on my limited knowledge, I think Neem oil is a very important subject to discuss and it would be nice to see some posts from experienced users.

cynthia_h · Posted: Thu Jun 04, 2009 4:12 am Post subject:

Neem oil is a product of the neem tree (Azadirachta indica), indigenous to India and neighboring countries/regions. Wikipedia has a good introductory article under the term "neem."

People in India have used neem tree products (its oil, twigs, powdered leaves, and I don't know what else) for thousands of years. For example, small twigs were used as toothbrushes before Western toothbrushes were introduced into India, and the twigs seem to have done a pretty respectable job.

I'm not sure when the plant-protective properties of the neem tree were discovered, but the tree has a very long history in India.

Cynthia H.
Sunset Zone 17, USDA Zone 9
_________________
"Though an old man, I am but a young gardener." Thomas Jefferson

David Taylor · Posted: Thu Jun 04, 2009 12:00 pm Post subject:

When I didn't get a response the first time around, I ended up at Wiki, but what no one seems to address is, how does it kill, or repel, bugs like aphids, but seems to have no affect on ladybugs. I had a pretty bad infestation in my cucumbers, sprayed the leaves, which appears to have killed the buggers instantly. Next day, I noticed quite a few ladybugs on the plants that appeared unaffected. I assume that Neem oil works mechanically, clogging up the aphids breathing apparatus or stripping away their flesh oil, like dishwashing soap does, otherwise it wouldn't be considered organic, right? Just curious.

cynthia_h · Posted: Thu Jun 04, 2009 1:43 pm Post subject:

Responses regarding mechanism of effectiveness are found under the scientific name of azadirachtin. I found a clutch of scientific studies using the search phrase

azadirachtin insecticide mechanism

and finally ended up at http://www.patentstorm.us/patents/5001149/description.html where, after enough digging, I finally encountered the statement that

"A natural plant compound which is known to inhibit ecdysis in insects, by some unknown mechanism, is azadirachtin."

It is known to inhibit molting (ecdysis), but the exact pathway is unknown.

Cynthia H.
Sunset Zone 17, USDA Zone 9
_________________
"Though an old man, I am but a young gardener." Thomas Jefferson