Subject: RE: What is neem?
From: [email-masked] (William M. Bode)
Date: 13 Jun 1994 15:49:54 -0400
Newsgroups: alt.sustainable.agriculture

Ian Staples wrote:

>I believe I read in _New Scientist_ not too long ago that chemists have
>succeeded in synthesising the active molecule, so that may be the end
>of the various schemes to become wealthy by growing neem in plantations,
>which have been promoted here in northern Australia in recent years.
>
>Also, I doubt that the leaves of neem have much by way of insecticide
>in them - that's extracted from the fruit kernal.  Our entomologists
>were getting frequent requests for control measures for leaf eating
>insect pests of neem here in NQ.  I understand that neem is related
>to our native "white cedar" (_Melia azidiracht_ [sp.?] ) which is
>seriously defoliated by insect pests quite regularly.
>--
>
>Ian Staples                        E-mail : [email-masked]

Greetings Ian and others:

_Melia azedarach_ Linnaeus, a tree of "West Asia," is also known in the
English language as "Persian lilac" and "Chinaberry."  Apparently it is
similar in appearance to neem but its flowers are bluish in color.
According to the literature I have read, its leaves and seed kernels on
average have lower concentrations of insect-deterring compounds than do
neem (_Azadirachta indica_ A. Juss) trees.

Unfortunately there are organisms which have evolved mechanisms to overcome
the chemical defenses of most plant species. Some insects which feed on
neem, e.g., oriental yelow scale, and some pathogens have been listed in
various publications. In the past year or two it was reported that there
was tree mortality, possibly from a root pathogen, in West Africa.

Many neem researchers think that even if a synthetic azadirachtin is
produced, insecticide made from neem kernel oil will be better because it
contains additional compounds which are detrimental to insects. Targeted
insect populations are much less likely to become resistant to a
combination of compounds having different modes of action than they are to
a single compound, i.e., azadirachtin. And what are the economics of
developing, manufacturing and registering a synthetic azadirachtin product?

I think it has been cited previously in DEVEL-L, but a good recent (1992)
review of the neem tree (_A.indica_) is _Neem, A Tree For Solving Global
Problems_, available from National Academy Press, P.O.Box 285, Washington,
D.C. 20055 for US$19.00.

Best regards,
Bill Bode

William Bode ([email-masked])
Entomology Dept., Penn State University
501 ASI Bldg., University Park, PA 16802
voice: 814-863-1854  fax: 814-865-3048