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Advice on Publications Available.Pest control using extracts from the Neem tree (Azadirachta indica) currently occurs in more than 55 countries throughout the world and neem products have been in use in parts of Asia, such as Burma and India for over 2,500 years.
Four years of trialing one neem extract ('Green Gold') on a wide range of crop and animal pests in northern Queensland has revealed potential for neem powders and ethanolic neem extracts to prevent insect pest attack throughout the year.
The growing worldwide demand for 'clean food' and better ecological approaches to pest control should be the stimulus for further research into the use of neem extracts. The potential for their use in the production of 'organic cotton' particularly warrants further investigation.
The active ingredients of neem extract include a group of seven constituents similar to, and including, the compound, azadirachtin. This compound has been shown to be a systemic feeding deterrent for insects (Gill and Lewis, Nature 232: 402-403, 1971). Azadirachtin does not kill pests, but it breaks life cycles and deters feeding, hatching, ecdysis (moulting) or any combination of these processes.
The most efficient use of neem extracts for pest control has been found to be against chewing and sucking insects, principally lepidopterous caterpillars and beetle larvae. The active ingredient accumulates in the growing tips of the treated plants, usually reaching functional levels within 24 hours of the leaves being sprayed. No other insecticidal products have the rapidity of systemic activity of azadirachtin.
The relative toxicity of neem extracts to non-target organisms is low. In toxicological testing conducted by the United States Environmental Protection Agency, it was not possible to establish an 'LD-50' for azadirachtin, because no symptoms were recorded, even at the highest dosage used. As a result, there is no 'residual' or 'withholding period' necessary following the use of neem extracts.
There is also a low likelihood of the development of resistance to neem extracts, especially if the treatment is used within an integrated program of crop management. Also, the cost of pest control with neem extracts is relatively low. In the developing world, neem leaf or fruit (kernels) produced by farmers from their own neem trees can supply no-cost or low-cost pest control. Australia has also developed a low-cost neem extract. The 'Green Gold' liquid neem extract has been produced at a lower cost than comparable US products.
However, there is a problem with the degradation of azadirachtin by ultraviolet light and daylight. Some producers bypass this problem by mixing neem extract with pyrethrum derivatives; the active constituents in the mixture synergise and are long-lasting.
Neem trees were first planted in the Northern Territory and north Queensland in the late 1930s. The first work on neem in Australia is believed to have commenced in 1968 at Weipa (Jamieson and Rice, QDPI FarmNote F17, 1988; Nicholson, 1992, personal communication to author).
Many pest species have been tested using neem extract. Bally (QDPI FarmNote, 1992) published partial lists of neem's official uses, diseases and pests. Rice (Fourth World Neem Conf., 1993) reported on the development of the neem industry in Australia; six insect pest species were listed as controllable at differing rates and concentrations of azadirachtin. Amongst the tropical pest species were locusts, three lepidopterous pests of cotton, one type of bug and two aphid species of cotton and corn.
At least five trials in cotton, conducted over recent years by Agrisearch Services Pty Ltd, Orange, NSW, have verified the extremely high efficacy of ethanolic neem extracts against Helicoverpa armigera in broad-scale cotton crops at Bourke, and near Moree in NSW and at Biloela in Queensland. It is possible that neem extract may be first fully registered for use on cotton.
The author has achieved high level control of a range of tropical pests over the past three to four years in field experiments on independent farms in several locations. For example, in northern New South Wales, the destructive wood-borer Agrianome spinicollis is being brought under control in an environmentally safe manner with the 'Green Gold' neem extract, injected under high pressure into the trunks of pecan nut trees in a large-scale orchard.
New Zealand's DSIR has reported good control of wool-carpet moth species, using 'Green Gold' neem extract.
An Australian patent is held by Dr Martin Rice of Brisbane for the mode of action of azadirachtin against sheep blowfly (Lucilia cuprina) , but this has not yet been commercially developed.
Neem extracts have also been tested in animal applications against fleas (Ctenocephalides felis), human applications against headlice (Pedicularis humanis capitus) and innovative ways to minimise tick and lice levels in livestock. Reports of neem extracts being efficient in controlling and preventing tick attack on cattle and horses, as well as giving relief from fly attacks to the head and rear of cattle and sheep, respectively, have been restricted to applications in dry times, possibly due to degradation of azadirachtin under other conditions.
In the future, plague locust, Schistocera spp, may be kept in check by the use of neem extracts. This use has appeal in developing countries due to the lower cost (Wilps, Nasseh and Krall, World Neem Conf., 1993). However, the seed or extract would have to be available and applied at the appropriate time. Neem extracts are apparently not being considered for investigation for plague locust control in Australia.
CSIRO research has suggested that at least one Australian neem extract, when vacuum coated into wood blocks, is capable of deterring termite feeding. Advanced trials are to begin shortly. The author has observed, in Cairns, North Queensland, that the Micracerotemes turneri species of termite died if a few mLs of concentrated ethanolic neem extract was placed into its nests.
Research at the University of Auckland (Dr G. Grandison) has confirmed Indian and European findings that neem extracts have a high efficacy against pathogenic crop nematodes, especially Meloidogyne javancia, other Meloidogyne spp and Pratylenchus spp. Australian primary producers may have the opportunity of using neem cake, instead of neem extract, for controlling such nematode species on lighter soils. Neem cake is processed from the material remaining after the crushing of the neem seed. Fertilisers mixed with neem cake have been applied to soil, prior to the planting of rice in India and other Asian countries for effective nematode control.
Although considered a 'medicinal plant species', neem requires a more ecologically-based research approach, requiring a long-term multi-disciplinary approach. The future of public-funded neem research in Australia is unclear. The Queensland Department of Primary Industries has carried out trial plantings and investigations on the neem tree and related research but the future of Australian research in neem is not clear.
There have been three international scientific conferences on neem and the uses of neem and four World Neem Conferences, to date (Rottach-Egern, Germany, 1980; Rauischholzhausen, Germany, 1983, Nairobi, Kenya, 1986 and Bangalore, India, 1993). The fifth World Neem Conference is to be held at the University of Queensland Gatton College in February 1996 (details are included in the section on conferences in this Newsletter).
One Australian company, Neem Oil Australia, based in Lismore, produces up to 100 kg of neem: azadirachtin-rich powder for commercial trialing annually. However, the costs of registering pesticides can often prevent small businesses from gaining registration for neem products in Australia. As well, registration takes time (O'Shea, Landcare Group Neem Workshop, Cloncurry, 1993).
Neem products registered in the US include those by Grace-Sierra (registered in 1990) and by Agridyne (1992). Both products have been registered, since 1993, throughout the US for 'all food and feed products'. Margosan-O, from Grace-Sierra gained registration in early 1992. The registration of these neem extracts means that Australia is lagging behind other parts of the world in the progressive development of more ecologically sustainable farming systems.
Conventional primary producers worldwide have been slow to take up the opportunities being presented by the increasing availability of neem trees for planting, and neem extracts and powders for insect control. Organic farming using products such as neem extract offers potential for a wider range of clean food and fibre products.
Any claims made by authors in the Australian New Crops Newsletter are presented by the Editors in good faith. Readers would be wise to critically examine the circumstances associated with any claims to determine the applicability of such claims to their specific set of circumstances. This material can be reproduced, with the provision that the source and the author (or editors, if applicable) are acknowledged and the use is for information or educational purposes. Contact with the original author is probably wise since the material may require updating or amendment if used in other publications. Material sourced from the Australian New Crops Newsletter cannot be used out of context or for commercial purposes not related to its original purpose in the newsletter
Contact: Dr Rob Fletcher, School of Land and Food, The University of Queensland Gatton College, 4345; Telephone: 07 5460 1311 or 07 5460 1301; Facsimile: 07 5460 1112; International facsimile: 61 7 5460 1112; Email:
r.fletcher@mailbox.uq.edu.au[
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