Affiliation: Ecotoxicology Program, Dept. of Entomology, Washington State University, Puyallup, Washington, U.S.A.
Published in: Journal of Environmental Science and Health, Part B, Volume 36, Issue 4 June 2001 , pages 457 - 465.
Abstract: "Although natural insecticides from the neem tree are generally perceived as less harmful to the environment than synthetic insecticides, new evidence indicates that these products may pose a risk to certain nontarget organisms. In this paper, acute and chronic effects of commercial neem insecticides on the aquatic invertebrate, Daphnia pulex were examined. The acute toxicity of two commercial neem insecticides, Neemix, Azatin and the experimental insecticide, RH-9999 to D. pulex was investigated using traditional 48 hr concentration-mortality estimates. Neemix and Azatin were equitoxic with LC50's of 0.68 and 0.57 ppm; RH-9999 was significantly less toxic with an LC50 of 13 ppm. A 10 d population growth study was conducted for Neemix and a Neemix formulation blank (Neemix devoid of the active ingredients) to determine whether the active ingredients of Neemix and/or components of the formulation were responsible for toxicity. D. pulex populations went to extinction after exposure to a Neemix concentration of 0.45 ppm azadirachtin (equivalent to the acute LC7). Neemix No Observable Effect Concentration (NOEC) and Lowest Observable Effect Concentration (LOEC) values for population growth were 0.045 and 0.15 ppm azadirachtin, respectively. The mean number of offspring per surviving female (Ro) declined in a concentration-dependent manner after exposure to Neemix with no offspring being produced after exposure to 0.45 ppm. Neemix NOEC and LOEC values for reproduction were 0.045 and 0.15 ppm, respectively. The formulation blank caused no mortality in the individuals used to start the population growth study but reduced reproduction and population growth accounting for 47% of the toxicity caused by Neemix at a concentration of 0.15 ppm. Thus, the formulation contributes substantially to the toxicity of Neemix but neem components are also toxic to D. pulex. Because the NOEC for population growth and reproduction were higher than the estimated environmental concentration of 0.035 ppm (a measure developed for forest pest mananagement), Neemix should pose little risk to populations of D. pulex."
In the paper "Effectiveness of Neem (Azadirachta indica) insecticides against Brassica pod midge (Dasineura brassicae Winn.)" the following is in the conclusion section of the full paper (which I have a copy of and can send to anyone interested): "It has been shown that azadirachtin can be accepted by plants through their root system and other tissues and distributed both intravascularly and intracellularly to different parts of tissues (Sundaram 1996; Wanner et al. 1997; Pavela et al. 2004; Pavela and Teixeira da Silva 2006). It is likely (according to our findings; it has not been published yet) that oilseed rape can accept azadirachtin through leaf stomata or skin and distribute it acropetally to other tissues, thus enhancing the persistence of azadirachtin�s effects, because it does not further decompose in the tissues and can protect the plant during the whole vegetation period (Pavela and B�rnet 2005)." henry_kuska z5 OH (email@example.com) in http://forums2.gardenweb.com/forums/load/roses/msg0609205313000.html
Safety evaluation of neem (Azadirachta indica) derived pesticides.
Boeke S, J Boersma MG, Alink GM, van Loon JJ, van Huis A, Dicke M, Rietjens IM.
Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, The
st_uids=15261960&query_hl=30&itool=pubmed_docsum The neem tree, Azadirachta indica, provides many useful compounds that are used as
pesticides and could be applied to protect stored seeds against insects. However in addition to
possible beneficial health effects, such as blood sugar lowering properties, anti-parasitic, antiinflammatory, anti-ulcer and hepatoprotective effects, also toxic effects are described. In this
study we present a review of the toxicological data from human and animal studies with oral
administration of different neem-based preparations. The non-aqueous extracts appear to be the
most toxic neem-based products, with an estimated safe dose (ESD) of 0.002 and 12.5
microg/kg bw/day. Less toxic are the unprocessed materials seed oil and the aqueous extracts
(ESD 0.26 and 0.3 mg/kg bw/day, 2 microl/kg bw/day respectively). Most of the pure
compounds show a relatively low toxicity (ESD azadirachtin 15 mg/kg bw/day). For all
preparations, reversible effect on reproduction of both male and female mammals seem to be
the most important toxic effects upon sub-acute or chronic exposure. From the available data,
safety assessments for the various neem-derived preparations were made and the outcomes are
compared to the ingestion of residues on food treated with neem preparations as insecticides.
This leads to the conclusion that, if applied with care, use of neem derived pesticides as an
insecticide should not be discouraged.