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Is neem oil superior to insecticial soaps and horticultural oils?

Posted by username_5 (My Page) on
Wed, Oct 12, 05 at 12:40

Hey all, I have been researching neem oil and some of the products using it.

Wanted to post a question to those of you here as someone on the veggy forum suggested you folks are very familiar with it.

OK, so here is the question. For killing soft bodied bugs on contact does it work at least as well as insecticidal soaps?

Next question: For controlling fungal issues does it work at least as well as milk/baking soda concoctions? Does it work just as well as the mineral oil based horticultural oils?

If your answers are yes to both I would assume neem oil is superior to any of the above products since it has the added benefit of screwing up bug life stages so they can't colonize.

Is there any reason I shouldn't use neem oil and prefer one of the other products?

Thanks in advance for your perspectives.


Follow-Up Postings:

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RE: Is neem oil superior to insecticial soaps and horticultural o

Neem oil is more toxic than insecticidal soaps would be and has different uses than horticulural oils. It is not superior although it does have its place in some gardens. This gets to the root of Integrated Pest Management and that you should start with the least toxic control needed rather than go to a more toxic substance first.


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RE: Is neem oil superior to insecticial soaps and horticultural o

It doesn't work well on Japanese Beetles.


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RE: Is neem oil superior to insecticial soaps and horticultural o

Really depends what you're wacking. It does kill a lot of pests, and does a job on many pathogens. It's pretty strong stuff though, and will kill things you don't want to kill.

If superior means "more lethal", it's superior. But then again some other organic sprays (nicotine, rotenone, pyrethrum) are quite lethal too, but can be pretty scary to mess with.


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RE: Is neem oil superior to insecticial soaps and horticultural o

What things does it kill that I wouldn't want killed? The reading I did on it indicated it didn't kill anything beneficial except bees if they were directly sprayed and I can avoid that.

I always try to avoid anything that will kill desirable organisms whenever possible which is why I chose the neem oil.

From what I read (although it didn't offer any evidence to back up the assertion) worm populations increased in soil where neem was used as a drench.

I am very interested in any literature that demonstrates the possible harmful effects of neem products.


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RE: Is neem oil superior to insecticial soaps and horticultural o

I'd dispute the contention that neem oil/extracts are more toxic than fatty acid-based insecticidal soaps. ANY substance, organic or not, can be toxic if applied in great enough concentrations. Neem has been used as an herbal remedy and dietary supplement by populations in its natural locale for centuries with documented beneficial effects. The big advantage to neem oil over other organic controls is its adaptability for numerous purposes, as both an insecticide and fungicide and as an effective control of other disease pathogens.

There is a very scholarly article on the pros and cons of neem oil/extracts available online, however it requires membership to the site or payment to download and view. A google search with the key words "neem oil, harmful side effects" should turn it up. Otherwise the attached is a good, well-rounded treatise on this organic control.

Here is a link that might be useful: Neem oil


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RE: Is neem oil superior to insecticial soaps and horticultural o

Thanks for the link GardenGal.

It indicated that while not everything has been tested there didn't seem to be much in the way of toxicity to beneficials which is consistent with what I have read elsewhere.


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sooty mold

is there some organic treatment for sooty mold? it is on many plants. help!

thanks, diana


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RE: Is neem oil superior to insecticial soaps and horticultural o

Sooty mold is not harmful to plants unless it is extremely severe - it can then disturb the process of photosynthesis. It is simply a harmless fungus that grows on the secretions (honeydew) of sucking insects, like aphids or scale. Just wash it of with regular water. Use a strong spray if on large plant, or just use a soft spray and your fingers if on a plant of more manageable size. Don't bother to do anything if on a deciduous plant - any affected foliage will be shed soon enough.


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RE: Is neem oil superior to insecticial soaps and horticultural o

The treatment for sooty mold is to kill the aphids. If they're not on a giant tree overhead, neem is actually pretty good for that.

Keeping the trees overhead well pruned to improve air circulation is the best OG control for aphids, as they're easily dislodged by winds if the canopy isn't too dense. Topping trees will make the problem worse, though.

On shrubs, reduce the density a bit, and make sure there are good nectar plants nearby. Syrphid fly adults eat nectar, while the larvae primarily munch on aphids.


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RE: Is neem oil superior to insecticial soaps and horticultural o

Answering you fungus control question, neem oil is mostly a preventative not very good for control of established disease. For powdery mildew on cucurbits, for example, milk and baking soda are a more effective control once the disease shows up, but I use neem oil earlier in the season to supress the fungal infection. This year, once the powdery mildew struck, I used a combination of milk and baking soda and neem oil, and found this better than either approach by itself to knock out and control the fungus.


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