In article , "pelirojaroja"
wrote:

Didn't do much when I was told to use it by a local nursery for a Japanese
Beetle infestation. The beetles eating the zinnias seemed completely
unfazed. Maybe they all died horrible deaths 3 weeks later -- maybe not.
The Neem Oil didn't act quickly enough in this particular instance. Never
had to use it for fungal/mite issues, so can't comment on those.

-- pelirojaroja

Michigan State University & Cornel studies have incciated that Neem kills
SOME beetle larvae that feed directly on a fully doused plant, or which
feed on insects that feed directly on a plant (including ladybug larvae),
but it does not kill adult beetles (including ladybug adults). It lowers
beetle fertility rate (includuing ladybug fertility) so in the long run
could lower overall beetle population (both harmful & beneficial types).
It's just not very harmful to adult beetles, & even as a larvae-killer it
has to get them at a delicate age & may require direct application with
only a smothering effect. As an insecticide per se it is at best mediocre
-- if it were otherwise, it'd would beneficial insects just as readily.
MSU stated that it repelled but did not kill beetles, whereas soapy water
did kill beetles (though only if the soapy water were sprayed directly on
the beetle). The MSU study also showed that neem oil's effectiveness as a
repellant lasted for ONE TO TWO DAYS; it did not show any systemic
protection which is commonly alleged, though other studies do indicate a
somewhat systemic effect of lowered insect fertility.

It's stronger use is for certain kinds of very troublesome funguses like
black spot, as shown in a separate Cornell study. I wouldn't use it for
mere powdery mildew because even sneezing on powdery mildew arrests it, &
tests at Cornell, Davis, & in Brazil have shown a milk spray both works
better & has less likely to have unwanted side-effect (like killing lady
beetle larvae or beneficial funguses), but for black-spot the milk spray
didn't work & neem oil scored high ratings (as preventative soil-drench,
not after-the-fact direct application to plants).

It had not been thoroughly tested before it became popular in the west
because frankly it reached our marketplace chiefly because it cost pennies
per drum from India but could be repackaged to sell dearly to Americans &
Aussies for extravagant profits. "Two thousand years of use in India!"
seems to have been "test" enough. I think it's never going to be seriously
indicted, but already some of its Magical Garden Benefits have been shown
to be less effective than than soapy water (for aphids or beetles) or milk
spray (for powedery mildew), & in the future other alleged super-uses will
probably be shown to be only moderately effective. And even where it
works, using gobs of it would not be good, though continued effectiveness
could require reapplication as often as ever 48 hours!

When the University of Washington study showedthat Neem lowered the
fertility rate of the adult lady bugs, so that without killing the adult
insect, it lowered the overall population of this garden helper, Green
Light neem oil as of 2001 removed the azadirachtin from their product,
which was thought to be the component that injured ladybugs -- but this
ended any value for the neem oil controling any insect at all, so Green
Light added pyrethrin to their neem brew to kill insects anyway. All other
brands of neem still contain azadirachtin. It WILL lower the ladybug
population (its effects on lowering the reproduction rate in many other
beneficial insects is assumable though not yet studied, since on those
species thus far studied the effects seems always to be present).

Soil-drench treatment for funguses was studied at Montana State
University, & without clear findings they suspected it was harmful to
large ornamental shrubs, though whether from long-term absorption of
repeat applications, or more likely due to destruction of beneficial
funguses (which are extremely essential for tree & woody shrub health) was
not established. They recommended using it only for small plants, plus
warned the neem soil drenchings had little affect in alkaline soils.

The idea that neem should be used for all things at all times, as often as
possible, never struck me as a good idea. I see some people praising it
like a wonder drug, & in many cases they are clearly just seeing what they
want to see, not what is provably the case. In Asia Minor it is used in
the form of neem sticks to clean teeth, it is in Asian mouthwashes &
toothpastes, & in a great many entirely unproven herbal remedies
recommended by herbal quacks in that unregulated industry. So a lot gets
ingested without notable injury, though double-blind studies seeking
potentially harmful effects seem not to exist, although a great many
double-blind studies in India were orchestrated solely for the Neem
industry's needs. This was already a powerful industry before their
economic power skyrocketed thanks primarily to American & Australian
gardeners' rather sudden & mainly unexpected delight in the stuff, &
China's equally unexpected embracing it as an herbal remedy for internal
use. So some of the studies prove antimicrobrial & fungicidal values &
some potentially medicinal values, without really assessing possible risk,
as the point is to extend the economic value, not actually to protect
public health with any negative finding.

There are "non profit" neem organizations throughout India that filter a
combination of government & temple & industry monies to all kinds of
projects just so long as they are oriented toward economic benifit. These
non-profits tend to be run by people with PhDs in theology or psychology
who want to promote "global goodness of Neem" even when putting all sorts
of doctoral names on studies. If you wanted t o paint your naked body in
dyed neem oil & hop round & round a stage flapping your arms to some tune
written by Satjit Ray, a love-song for Kali personified as a Neem Tree,
you could get funding for it in India. If you wanted to test possibly
harmful side effects with a serious double-blind study, you'd be out of
luck.

Australia is joining the research-for-profits crowd & generating careless
research in support of a new neem industry there, but I expect there'll
also be some serious research with some real findings out of Australia as
there can't so easily be out of India, where it would go even against Maha
Devi the Great One to find out & reveal anything bad. Horticultural &
entymologicial studies at numerous universities in the USA are presently
under way. I'd expect these studies to find some bad & some good; some of
them have already shown fewer values than alleged, or weaker values than
older organic options.

Some of the extant studies (in India) are so biased for the industry
they'll never tell you that while some skin-care values can be shown with
application of neem oil, they do not equal or exceed the equally smelly
value of fish oil, basil oil, or motor oil, or that neem has the higher
risk of irritation -- so the "proven" value is somewhat a statistical
illusion. A few therapeutic uses have already been disproven, but not by
any of the India studies. Another dubious study shows that neem oil kills
mosquito larvae & lowers adult mosquito fertility, but the reality again
is salad oil shares some of the effect; the study compared egg-hatching &
wriggler survival in water treated with two different preparations of neem
& compared that to water untreated with anything -- a basic India-style
study the whole point of which is to help sell more Neem, ultimately
"proved" only that neem works better than doing nothing, yet the study is
the basis of marketing neem willynilkly for mosquito control.

Because the neem tree is sacred to the Maha Devi, the Mother Goddess in
India, magical & religious significance clouds clear judgement, & on top
of that is the economic juggernaut of neem agribusiness. So it is used for
cancer, arthritis, & smallpox with many other allegations of magical
benifit. One infamous & preposterous study "proved" neem was as effective
as a chief rival, Ginkgo biloba. At least, that was the finding after the
study had been recast by herb peddlars. The study actually showed that
both were as effective as placebo!

A few credible studies do seem to support the idea that it is in the main
harmless to people & pets. When rats were fed Neem in controlled tests, it
never reached a toxic level, but rats actually gained weight with neem in
their diet. It is believed POSSIBLY to have a contraceptive effect on
mammals (on humans or one's champion terrier...) just as it does on some
insects; it may be too harmful to sensitive larvae of beneficial insects &
useful bacteria; allergic responses are a commonplace; & it is a
potential hazard when it gets into wounds.

-paghat the ratgirl

--
"Of what are you afraid, my child?" inquired the kindly teacher.
"Oh, sir! The flowers, they are wild," replied the timid creature.
-from Peter Newell's "Wild Flowers"
See the Garden of Paghat the Ratgirl: http://www.paghat.com/