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The chemical compounds have been reported to be exuded by plants and their inhibitory effects of other plants. The research work was carried out to study the allelopathic effect of root, bark and leaf extracts of Azadirachta indica L. on the seed germination of Abelmoschus esculentus L. Germination studies were conducted in laboratory, the bhendi seeds treated with the root, bark and leaf extracts of Neem. On the seventh day the morphological parameters, photosynthetic pigment and biochemical contents were analysed. The result showed that the rate of germination of bhendi decreased in all Azadirachta indica L. extracts. The reduction in biochemical contents of bhendi was also noted. The highest rate of germination was observed in control (distilled water) treatment and the highest rate of inhibition was observed in root extract followed by bark and leaf extracts.
The effects on growth of Tilapia zilli exposed for 12 weeks to sublethal crude extracts of Azadirachta indica was investigated in static bioassays and a constant aeration system. Weight increased with the decline of nominal concentrations of the extracts. Long-term exposure of T. zilli to sublethal concentration of the extract caused growth retardation. The exposed fish showed abnormal behavioural responses at 1.56 and 0.78 mg dm-3, these responses being minimal at lower concentrations. The use by local fishermen of extracts of A. indica to kill fish is therefore ill-advised.
Fossil fuel resources are decreasing daily while biodiesel fuels are attracting increasing attention worldwide as blending components or direct replacements for diesel fuel in vehicle engines. In this experiment the seed oils of 30 Neem (Azadirachta indica. A. juss) biotypes were screened and evaluated for their physio-chemical parameters for oil content, biodiesel yield, density, viscosity, iodine value , free fatty acid and saponification value. Hence the neem seed oil tested in this current study could be the potential sources of raw material for biodiesel production.
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Twenty five years of azadirachtins (1986-2011)

72%
Azadirachtins are known as phagorepellent natural products from seeds of the neem tree Azadirachta indica A. Juss (Meliaceae), which impede the development of larval insects and sterilize adults. The labors of the past three decades ultimatively lead to a chemical structure, which has been unanimously but independently elaborated by German, British and American authors. This structure is in force ever since 1985/87 and was ultimately confirmed by Veitch & al. in Ley’s group in Cambridge, England, through total synthesis. Its 25th birthday is presently being celebrated. Marrangin (=Azadirachtin L) was discovered in Gießen and chemically identified by Kalinowski and colleagues. It occurs in seeds of the marrango tree, Azadirachta excelsa (Jack) Jacobs. In some insect species but also in mites like Tetranychus urticae, its biological activity is significantly superior to azadirachtin A. The value of these biorational compounds, with their very low vertebrate toxicity, and their low toxicity today is globally recognized. Quite recently, azadirachtin and analogues gain acceptance in veterinary and human medicine.
The neem tree, Azadirachta indica A. Juss, is virtually free of insects, mites, and nematodes due to natural substances present in the leaves, roots and kernels. The whole tree is bestowed by nature with an ultimate resistant system which always effectively repels and starves various pests. Neem extracts containing azadirachtin exhibit anti-feedant, repellent, and growth regulatory effects against various pests. Predators and parasites are not affected by neem extracts, and therefore the neem products are ideally suited for integrated pests management concepts. Several botanical insecticides based on neem extracts (e.g., NEEMIX, BioNEEM, Margosan-O, Sukrina 75 EC, Neemark, Nimbosol, Repelin, Wellgro) are available for effective management of whiteflies, leafminers, lepidopteran and coleopteran larvae, locusts, cicadas, aphids on a variety of growing crops and raw agricultural commodities in the field.
Neem (Azadirachta indica A. Juss.) seed oil (NSO) is acclaimed to have some form of insecticidal action against more than 400 insect species in at least 10 to 13 orders. The main delimitating factor in the wide acceptance of this well tested plant as a storage pest bioinsecticide is its foul sulfurous smell and bitter taste which impinges on the acceptability and marketability of treated produce. To ameliorate this shortfall, therefore, an assessment of the potential of impregnating different storage materials; [plastic containers (PLC), Bagco bags (BCB), Black polyethylene bags (BPB), white polyethylene bags (WPB) and calico bags (CAB)], with NSO in the management of Callosobruchus maculatus (F.) in stored Bambara seeds (Vigna subterranea L.), was conducted in the laboratory. The experiment was laid out in a 4 x 5 factorial arrangement fitted into a completely randomized design (CRD). Factor A represented four concentrations of NSO (0.00, 0.50, 1.00, 1.50 ml/ 100g seed), while factor B were the five different storage materials. The treatments were replicated four times Generally, seeds stored with impregnated storage materials recorded more bruchids mortality, reduced oviposition rate, decreased number of emerged insects (F1 and F2) and had less damaged seeds (and hence decreased weevil perforation index, WPI) than the control. Concentration performance was dose related though the highest (1.50 %) did not differ statistically (P=0.05) from the medium (1.00 %) concentration. Seeds stored in BPBs had the highest mortalities, but recorded the lowest in number of eggs oviposited, egg/seed ratio, F1, F2 and cumulative emergence, respectively. These results differed significantly (P=0.05) with the seeds stored in other materials. BPB stored seeds were also the least damaged with lowest exit holes/seed, seeds with holes and WPI, respectively. The performance of BPB was closely followed by seeds stored in WPBs in all the parameters tested. Conversely, seeds stored in BCBs recorded the lowest mortalities but the highest in all other parameters assessed. Other storage materials (PLC and CAB) had better storage quality than BCB materials. Impregnation of storage materials with NSO could be a better option to direct seed application with its attendant drawback. The use of NSO impregnated black polyethylene bags, within the scope of the storage materials screened, to control damage by C. maculatus in stored Bambara seeds, should be encouraged.
Azadirachtin is the most active substance separated from Azadirachta indica. lt acts destructively on numerous species of insects and mites. The aim of the presented investigations was to determine the effect of azadirachtin on one of the most dangerous pests of cabbage plants, Pieris brassicae, and on its natural enemy, Apanteles glomeratus. The results of the field observations did not show any repellent effect of azadirachtin relating to laying their eggs cabbage butterflies. However, a significant effect of the azadirachtin solution on reduction the number of cabbage butterfly caterpillars (it was more distinctly marked in respect to young larva stages) as well as on limited feeding by caterpillars. No negative influence of azadirachtin on a parasite of Pieris brassicae caterpillars, Apanteles glomeratus was distinctly shown.
Seeds of local trees, such Azadirachta indica A. Juss, Adenanthera pavonina L., Leucaena leucocephala (Lam.) de Wit and Eucalyptus spp., were used as aqueous extract at 25, 50 and 100 % concentration to control the activity of Meloidogyne javanica (Treub) Citwood. All seed extracts showed lethal effect on M. javanica eggs, and a gradual decrease in egg hatching and an increase in mortality of second-stage juveniles were observed with the increase in extract concentration. L. leucocephala was found to be most effective in reducing egg hatching, whereas 100 % mortality of juveniles was observed in the case of A. indica seed extract. Number of knots was significantly reduced at 100 % concentration when seeds of chick pea and mung bean were treated and soil was drenched with A. pavonina and Eucalyptus spp. seed extract.
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