Effects of neem (Azadirachta indica) extracts onLeptocorisa chinensis under choice and no-choice conditions

Two extracts from neem (Azadirachta indica A. Juss. (Meliaceae)) seeds, azadirachtin and oil, and a mixture of neem oil and abamectin, were tested on second-instar nymphs of the rice bugLeptocorisa chinensis (Dallas) (Hemiptera: Alydidae). To clarify the effect of spraying coverage on bioefficacy of test materials, experiments were conducted under choice and no-choice conditions in field cages. In a choice test, treatment with the mixture of neem oil and abamectin was most effective in reducing the survival ofL. chinensis, followed by azadirachtin at 60 ppm, 30 ppm and 3% neem oil, whereas all treatments except neem oil caused 100% mortality within 3 weeks in a no-choice test. When second-instar nymphs had choices of treated and untreated plants within a treatment, no differences in yield and sum of dead and stained grains were found between those two choices, indicating that nymphs neither caused significant reduction in yield nor reduced the quality of untreated plants. Regardless of treatment, the difference in overall yield between treated and untreated plants under choice conditions was not statistically significant (P>0.05). Our results indicate that neem-based formulations, used alone or in combination with abamectin, have the potential to be integrated into the existing programs to control the rice bug. http://www.phytoparasitica.org posting Aug. 28, 2005.     

effects of neem(Azadirachta indica) seed kernel extracts from different solvents on the predacious mitePhytoseiulus persimilis and the phytophagous miteTetranychus cinnabarinus

The effects of neem seed kernel extracts from different solvents on the predacious mitePhytoseiulus persimilis Athias-Henriot and the phytophagous miteTetranychus cinnabarinus (Boisd.) were compared. All extracts were much more toxic to the latter pest than to the former. Using the respective LC₅₀ for the two species, the toxicity index (LC₅₀ Phytoseiulus/LC₅₀ Tetranychus) was found to be 3 for the methanol, 4 for the ethanol, 23 for the acetone, and 58 for the pentane extract. The order of toxicity of the extracts (pentane > acetone > ethanol > methanol) was valid only forT. cinnabarinus. The EC₅₀s for reduction of fecundity were rather close for the two species.     

Effects of neem (Azadirachta indica) seed kernel extracts from different solvents on the carmine spider mite,Tetranychus cinnabarinus

Extracts of neem (Azadirachta indica A. Juss) seed kernels prepared from various solvents affected the behavior and fecundity of the carmine spider mite,Tetranychus cinnabarinus (Boisd.). Bean leaf discs freshly sprayed with different concentrations of the extracts strongly repelled the females from the treated leaves and egg-laying was reduced. On the basis of EC 50s for both parameters, the order of effectiveness of the extracts was pentane > chloroform >n-butanol > acetone > methanol > H₂ 0 (inactive). The activity decreased with increasing dielectric constant of the extracting solvent. The chloroform and butanol extracts in the original solvents were phytotoxic. Bean leaf discs 7 days after spraying with the pentane and acetone extracts, still caused mortality and reduction in fecundity of adult females, but no repellency. The acetone and the pentane extracts sprayed directly on adult female mites on bean leaf discs, caused repellency and reduction of fecundity and also mortality of adults.     

Activity of neem (Azadirachta indica A. Juss) seed kernel extracts against the mustard aphid,Lipaphis erysimi

An aqueous, an ethanolic and a hexane extract obtained from neem(Azadirachta indica A. Juss) seed kernels were tested for insecticidal activity against the mustard aphid,Lipaphis erysimi Kalt. The hexane extract, which exhibited a much higher activity than the two other extracts, had an LC50 of 0.674%. When the hexane extract was partitioned with ethanol, the ethanol-soluble fraction had an LC₅₀ of 0.328%, whereas the ethanol-insoluble part showed no activity even at 1%. Column chromatography of the ethanol-soluble fraction yielded eight compounds: nimbin, epinimbin, desacetylnimbin, salannin, desacetyl-salannin, azadirachtin and two unidentified compounds — a salannin derivative and a nonterpenoid. Of these, only five could be tested. Nimbin and epinimbin exhibited no toxicity at 0.3%, whereas salannin, a salannin derivative and the non-terpenoid gave LC₅₀ values of 0.055, 0.096 and 0.104%, respectively.     

Efficacy of neem plant (Azadirachta indica) extracts in the control of Trogoderma granarium,a pest of stored groundnuts

Journal of Plant Diseases and Protection - Petroleum ether extracts of leaves and kernels of the neem plant, Azadirachta indica A. Juss, mixed at varied dosages of 0, 50, 150, 250, 350 and 500...     

Production of desert locust feeding deterrents from in vitro cultured neem (Azadirachta indica)

Callus was initiated from cotyledon, hypocotyl and shoot tip explants of neem seedlings (Azadirachta indica A. Juss.) that were cultured on Murashige and Skoog (MS) agar medium supplemented with MS vitamins, casein hydrolysate, indole-3-acetic acid and benzylamino purine. Shoots regenerated from hypocotyl-derived callus only. Mature 10-12-week-old callus regenerated both shoots and somatic embryos (SEm). The antifeedant activity of different types of callus, leaves and SEm was determined with larvae of the desert locust Schistocerca gregaria in a no-choice feeding bioassay. In vitro tissue-cultured neem had antifeedant properties against the desert locust. To the best of our knowledge the antifeedant activity of neem somatic embryos extracts is reported here for the first time.     

The different effects of two preparations of neem (Azadirachta indica) and of Sumicidin® on the aphid predator Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae)

Journal of Plant Diseases and Protection - Greenhouse experiments were conducted at Khartoum (Sudan) with the aphid predator Hippodamia variegata, two botanical and one synthetic insecticides: neem...     

The production of azadirachtin by in-vitro tissue cultures of neem,Azadirachta indica

Callus produced from leaves of a Ghanaian strain of the neem tree, Azadirachta indica A. Juss has been shown to produce the natural insecticide azadirachtin when grown in a defined medium. The azadirachtin was isolated by standard procedures of solvent partition and column chromatography monitored by supercritical fluid chromatography. Biological activity was monitored with antifeedant tests using the desert locust (Schistocerca gregaria Forsk.). The azadirachtin was identified by chromatography on three independent chromatographic systems (SFC, HPLC & TLC) and two thin-layer colour tests. It has 100% antifeedant activity at < 0.04mg litre^?1. The yield of azadirachtin was 0.0007% based on dry weight of callus.     

Comparison of anti-feedant and insecticidal activity of nimbin and salannin photo-oxidation products with neem (Azadirachta indica) limonoids

Photo-oxidation of the neem limonoids nimbin and salannin with UV light in the presence of oxygen gives two isomeric lactone products per limonoid, nimbinolide and isonimbinolide, and salanninolide and isosalanninolide, respectively. When compared in insect tests with the important limonoids of neem seeds, azadirachtin, nimbin and salannin, isonimbinolide and isosalanninolide show activity greater than that of nimbin or salannin and in some respects show activity approaching that of azadirachtin. The photo-oxidation products were tested for anti-feedant activity and toxicity against larvae of three species of Lepidoptera, Spodoptera littoralis (Boisd), Spodoptera frugiperda (FE Smith) and Helicoverpa armigera (Hübner) and nymphs of the locusts Schistocerca gregaria (Forsk?l) and Locusta migratoria (L).     

Toxicity of neem (Azadirachta Indica) seed kernel extracts prepared with different solvents,on the spider chiracanthium mildei

The toxicity of neem seed kernel extracts prepared with different solvents against the predatory spider,Chiracanthium mildei L. Koch, was investigated. The order of toxicity of the 4% extracts was pentane < acetone < ethanol << methanol = water (nontoxic). All extracts were nontoxic at 2.5%.     

Noxious effects of neem extracts onCrocidolomia binotalis

The potential of neem extracts to control the cabbage webworm,Crocidolomia binotalis Zell. (Lepidoptera: Pyralidae), was investigated in the laboratory. Neem, besides being an antifeedant at as low as 0.001% of the methanolic extract, was shown to be very toxic, as evidenced by high larval mortality and poor emergence. It also caused disruption of normal development: significant delays in larval moults, appearance of permanent larvae in the 3rd and 6th instars, and abnormal pupation. A possible interference with hormonal activity is discussed.     

Influence of carrier solvent on the efficacy of neem (Azadirachta indica A. Juss) seed oil applied for the control of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Journal of Plant Diseases and Protection - The influence of four carrier-solvents (acetone, ethanol, petroleum ether and hexane) on the efficacy of neem (Azadirachta indica A. Juss) seed oil...     

Nematicidal Potential of the Neem Tree Azadirachta indica (A. Juss)

Plant products are receiving greater attention as prophylactics against several species of plant-parasitic nematodes. Numerous experiments have shown the potential nematicidal value of plant parts and their by-products when incorporated into soil or when the plants themselves are interplanted as seedlings among crop plants. Various products (oils, cakes, extracts, etc.) prepared from the leaves and seeds of the neem plant (Azadirachta indica A. Juss) (Family Meliaceae) have been reported as effective protectants against nematode pests when used as root-dips and seed treatments. Nemato-toxic compounds of the neem plant, especially the azadirachtins, are released through volatilization, exudation, leaching and decomposition. The modes of action of these compounds are complex, and a number of mechanisms in relation to nematode management are yet to be fully explored. This review critically assesses the potential of these products in the management of nematodes in tropical agriculture.     

Neem oil (Azadirachta indica) nanoemulsion--a potent larvicidal agent against Culex quinquefasciatus

BACKGROUND: Nanoemulsion composed of neem oil and non‐ionic surfactant Tween 20, with a mean droplet size ranging from 31.03 to 251.43 nm, was formulated for various concentrations of the oil and surfactant. The larvicidal effect of the formulated neem oil nanoemulsion was checked against Culex quinquefasciatus. RESULTS: O/W emulsion was prepared using neem oil, Tween 20 and water. Nanoemulsion of 31.03 nm size was obtained at a 1:3 ratio of oil and surfactant, and it was found to be stable. The larger droplet size (251.43 nm) shifted to a smaller size of 31.03 nm with increase in the concentration of Tween 20. The viscosity of the nanoemulsion increased with increasing concentration of Tween 20. The lethal concentration (LC₅₀) of the nanoemulsion against Cx. quinquefasciatus was checked for 1:0.30, 1:1.5 and 1:3 ratios of oil and surfactant respectively. The LC₅₀ decreased with droplet size. The LC₅₀ for the ratio 1:3 nanoemulsions was 11.75 mg L^?1. CONCLUSION: The formulated nanoemulsion of 31.03 nm size was found to be an effective larvicidal agent. This is the first time that a neem oil nanoemulsion of this droplet size has been reported. It may be a good choice as a potent and selective larvicide for Cx. quinquefasciatus. Copyright © 2011 Society of Chemical Industry     

Toxic and residual effects of Azadirachta indica,Tagetes erecta and Cynodon dactylon seed extracts and leaf powders towards Tribolium castaneum

Journal of Plant Diseases and Protection - Direct and residual toxicities of seed extracts and leaf powders of the neem tree (Azadirachta indica), marigold (Tagetes erecta) and durba (Cynodon...     

Neem (Azadirachta indica) seed kernel extracts and azadirachtin as oviposition deterrents against the melon fly (Bactrocera cucurbitae) and the oriental fruit fly (Bactrocera dorsalis)

Neem(Azadirachta indica A. Juss.) seed kernel (NSK) extracts,viz., NSK aqueous suspension (NSKS), ethanolic extract of NSK (EtOH. NSK), hexane extract of NSK (neem oil), ethanolic extract of the hexane extract (EtOH. oil) and acetone extract of deoiled NSK powder (Acet. DNSKP) at 1.25-20% concentrations, and pure azadirachtin at 1.25-10 ppm, were evaluated as oviposition deterrents toBactrocera cucurbitae (Coq.) andB. dorsalis Hendel. NSKS at ≥5% under choice test conditions, and at all concentrations (≥1.25%) in no-choice tests significantly deterred oviposition in both species. Similarly, EtOH. NSK was significantly active at all the concentrations tested for both species in choice and no-choice tests. However, with neem oil and EtOH. oil sensitivities of the two species differed considerably. Both extracts deterred oviposition byB. cucurbitae at all the concentrations tested under both choice and no-choice test conditions. On the other hand, withB. dorsalis, neem oil was significantly deterrent only at 20% in both test regimes and at 5% and 20% for EtOH. oil under choice and no-choice test conditions, respectively. Acet. DNSKP significantly deterred oviposition by both species at all concentrations tested. Azadirachtin failed to deter oviposition in either species.     

Microbiological and Chemical Analysis of Neem (Azadirachta indica) Extracts: New Data on Antimicrobial Activity

The antimicrobial effects of extracts of neem seed (Azadirachta indica A. Juss.) were investigated using microbial growth inhibition assays. A laboratory-prepared neem seed extract along with a commercially available formulated product, were characterized using HPLC, and shown to be effective against a range of bacteria in an agar diffusion assay. The active ingredient,i.e., the unformulated seed extract of the commercial product, also showed activity and this was further investigated in a biochromatogram, using the sensitive bacteriumBacillus mycoides. Results showed antibacterial activity as three discrete inhibition zones that did not correspond to the R_f of the major neem metabolites, azadirachtin, nimbin and salannin. This suggests that these compounds were not antibacterial. The colony radial growth rates of the fungal pathogens that cause ‘take-all’ and ‘snow mould’ disease were both significantly affected when the commercial, unformulated, neem seed extract was incorporated into the growth medium. Experiments in liquid culture suggested that the effect was fungistatic. Conidial germination of the commercially important obligate pathogenSphaerotheca fuliginea (powdery mildew) was reduced to 11%. The results show that neem seed extracts possess antimicrobial activity with notable effects on some fungal phytopathogens. This Work demonstrates that neem seed extracts have potential for controlling both microbial and insect pests. http://www.phytoparasitica.org posting Sept. 16,2001.     

Response ofTearias Insulana boisd. larvae to neem (Azadirachta Indica a. juss) Kernel extract

The effect of Neem on the development ofEarias insulana Boisd. was investigated. Different concentrations of an aqueous extract of Neem kernels were incorporated in a semi-synthetic diet and larval growth, pupation rate and mortality of larvae were recorded. Neem was highly effective against 7-8- and 12-day-old larvae at all concentrations ranging between 0.075 and 1%. The systemic activity of Neem was investigated by standing cotyledons of a glandless cotton strain with their petioles in different concentrations of Neem. After 72 hours feeding at all concentrations tested, larval weight was about half that on the untreated leaves.     

Acute and chronic effects of neem on Myzocallis coryli (Homoptera: Aphididae)

Abstract

Adults and immatures of the filbert aphid, Myzocallis coryli (Goetze), a major pest of hazelnuts worldwide, were exposed to foliage treated with different concentrations of a botanical insecticide, Margosan-O, derived from extract of neem seeds. Both mature and immature stages were highly sensitive to this compound. Acute toxicity causing immediate mortality of young nymphs, particularly at higher rates (50 ppm or more), and chronic effects resulting in reduced offspring production, lengthening of nymphal development time and reduced survival of subsequent generation were recorded. The offspring production of adult aphids fed on treated leaves was reduced in a dosage-dependent manner, nearly 50% at 2.5 ppm to over 80% at 62.5 ppm. However, no nymphal survival was recorded at 25 ppm or higher doses. A repellency effect was also recorded, butthe feeding deterrence response was weak at best. Field trials also showed a marked reduction of aphid numbers on treated foliage, suggesting the effectiveness of neem against this major pest of hazelnuts.