Neem Oil

[opabinia51]

So what exactly is Neem Oil? And what is it's purpose?


I'm placing this thread on Neem Oil from earlier last year as a Sticky to answer peoples question about insect control.

Our answer to insect problems is usually: Neem Oil. but, I think that it is important that people know about Neem Oil and it's effects. (Not to say that it is a really bad thing )

Anyway, I recommend that people give this thread a read.

[grandpasrose]

Neem Oil is used in the garden as a non-toxic botanical pesticide. It coats the surface of the plant, preventing the germination of fungal and and other sorts of plant ailments.
It also repels insects from your plants because they prefer not to eat anything with the oil on it, and die of starvation, and lessen in numbers because they then have fewer remaining bugs to provide offspring.

It is made from the fruit, seed and leaves of the Neem Tree, which originated in India, but is now grown in several countries, and some even grow it as a house plant.
It also has herbal qualities that have been used for centuries on a number of ailments.
Hope this helps!
VAL

[The Helpful Gardener]

I have used it successfully as a fungicide, a miticide, and an insecticide without ill effect to plants, animals or people. It is easy and harmless to use and provides efficacious results, with quick breakdown in the environment. What's not to like?

Scott

[opabinia51]

BONUS! Thanks for the information Scott. I'll have to invest in a bottle of neem oil. All information is good information.

[Guest]

Neem Oil is not harmful to beneficials? Ladybeetles, bees, parasitic wasps, etc?

[grandpasrose]

Not at all. Neem oil is not toxic. It acts as a non-feedant, meaning the nasties just won't eat it, and since it is on the plant, and they live on plants, they starve. The insects that don't eat plants are not affected at all.
The oil also acts as a fungicide and miticide by coating and smothering them.
It has no effect on animals, humans, etc.
VAL

[opabinia51]

Thanks for bringing that up, I want to look into exactly what chemicals are in Neem Oil. I'll post what I find on here.

[opabinia51]

Okay, Neem oils main constituent is a group of chemicals known as tetranortriterpenoids in particular azadirachtin. Azadirachtin has the following properties:

- Disturbing or inhibiting the development of the eggs,
larvae, or pupae.
- Blocking the molting of larvae or nymphs.
- Disturbing mating and sexual communication.
- Repelling larvae and adults.
- Deterring females from laying eggs.
- Sterilising adults
- Deterring feeding

So, that said. Tetranotriterenoids are plant produced chemicals that seem to mimic insect hormones known as ecdysones. Tetranotirteraenoids are structurally similar to ecdysones. Ecdysones are used by insects to control the process of metamorphosis. Azadirachtin appears to block the production of ecdysones by insects. Therefore, insects (in general) will not molt, thus interrupting their lifecycle.

Also, Azadirachtin acts as a feeding deterrant for some insects. After ingestion of the chemical, insects become quiescent and stop feeding.

As far as toxic affects on animals other than insects, Azadirachtin (the main chemical constituent of Neem Oil) can be a minor skin and eye irritant to mammals (rats, rabbits, guinea pigs were tested) and seems to have no sexual side effects on mammals. (Spermatogenesis in rats is not affected).

No other toxic effects were found on animals other than insects.

But, in answer to the question: Neem Oil does seem to affect all insects indiscriminately. Of course, as Val pointed out, it has to be ingested. I did not find any information on the volatility of Azadirachtin so, I don't know if the vapours will have an affect on insects near the plants sprayed with the chemical.

However, I also discoverd that Azadirachtin does seem to be harmless to:spiders, butterflies, and insects such as bees that pollinate crops and trees, ladybugs that consume aphids, and wasps that act as parasites on various crop pests.

And I found another study which states that after repeated spraying of highly concentrated neem products that worker bees carried pollen grains back to the hive that wer fed to the brood. In this case, the concentration of Azadirachtin had a concentration that was high enough to affect the bees and in small hives the resultant populations exhibited the growth regulating affects of Azadirachtin. However, in Medium and large sized hives, there was no effect.

Azadirachtin does not seem to accumulate in the environment and breaks down in the soil or water.

Basically, Neem Oil seems to be safe to use provided that it is not repeatedly sprayed on plants. And even when it is; it's toxicological effects seem to be minimal. But, I would still recommend not spraying regularly with it. (North America's bee population has enough trouble right now)

[grandpasrose]

Well there you go! You answered your very own question!
As with all good things in life, moderation is the key.
VAL

[opabinia51]

Yah, I guess I did. Well, she pushed me in the right direction for research though, and you gave me some hints for my search. That's what is great about this site, we all work together to get great information for ourselves and everyone else.

[Guest]

You mention the one concern I still have: The safety of bees. I have one of the few gardens in my area with a large number of bees, and a good cross section of other beneficials, butterflies and ladybettles. I've noticed this the last two years in which I've used only organic fertilizers. When I see a problem leaf I clip it off and when I see troublesome insects I either blast them with the hose or knock them into ammonia water with a bit of murphy's oil soap.

The bee population has been so hard hit in the mid-west that I'm still not sold on the neem oil thing. Will re-read and consider your informative post. My intitution still thinks not. A person not having bee decline may dismiss my concern, but there is a definite drop in fruit and flower pollination in this area. Bee keepers here resort to wintering their hives at a bee hospital in Texas for treatment of the virus that is all but wiping out the native bee population.

[opabinia51]

Actually, that is a wise choice. Given that in the research that I read, small hives of bees were affected by the ingestion of pollen containing Azadirachtin and given that the population has been hit so hard, I would say that hives are most likely a lot smaller. So as always, best to ere on the side of caution.

Of course, according to the research: this means that one does not have to discontinue using Neem Oil, it means that one should only use small amounts of it.

[grandpasrose]

As I have said previously, all good things in life must be used in moderation, or they are no longer good!

On the other side of the equation, neem oil has been found to be highly safe to bees. In fact, using neem oil as advised helps to cure Nosemosis and is widely used in the bee keeping industry to as a botanical method to treat varroa and tracheal mite problems of bees, which can decimate an entire colony at once.

Because neem products are used for human consumption and medication, exposure to neem in the process of treating plants with neem oil poses no threat to humans or other higher animals. Moreover, neem is not harmful to beneficial insects, affecting only those insects feeding on plants treated with neem. Since most predator insects do not also feed on plants, they are not harmed by the presence of neem. Neem biodegrades in a matter of weeks when exposed to sunlight or in soil.

Neem-based products have been extensively tested and are as effective insecticides in commercial greenhouses. The Neem seed has been the subject of extensive testing throughout the world since World War II. Neem has been tested at major universities throughout the U.S. and Canada since 1982.
In EPA testing, establishment of an LD-50 proved impossible as azadirachtin, present in neem oil, was asymptomatic at all levels tested. Accordingly, there are no reentry or residual restrictions associated with the use of neem oil.

So, as with everything else, weigh the pros and cons of any product before you use it!!!
VAL

[The Helpful Gardener]

You are most correct in your concerns (sift through my posts on pollinators and you'll see that I am VERY adamant on the subject), but barring direct application, this is not harmful to bees, or any other pollinators...

THat said it is hard to not apply to some pollinators (they continue to refuse to read my REI postings! ), but comparitively, this is a very safe solution...


Scott

[opabinia51]

I hear you Val when you say that Neem Oil is only harmful to insects that feed on the plants but, a lot of beneficial insect do actually feed on the pollen and in the articles that I read, Neem Oil is harmful to insects (in particular Bees) when Neem Oil is in high concentrations.

When used in high concentrations or when it is over applied the azadirachtin concentration on pollen grains becomes high enough to become toxic to insects that feed on the pollen.

Suffice to say that Neem Oil should be used in moderation.