Abstract

ESPARZA-DIAZ, Gabriela et al. Azadirachtin concentration, insecticide efficacy and phytotoxicity of four neem Azadirachta indica A. Juss. extracts. Agrociencia [online]. 2010, vol.44, n.7, pp.821-833. ISSN 2521-9766.

The preparation of effective neem-based bioinsecticides (Azadirachta indica A. Juss.) requires the extraction and concentration of its active ingredients, given that they are not found in large quantities in a natural form. Simple cold press, methanolic cold press (methanolic), Soxhlet-hexane (hexanic) and aqueous (aqueous) neem extracts were compared with respect to the concentration of azadirachtin (AZA) and its insecticidal effectiveness against Aphis gossypii Glover, as well as possible toxic effects on Ixora coccinea L. The experimental design was completely randomized. An analysis of variance was made with the data and the means were compared with the Tukey test (p≤0.05). Analyses of extracts by HPLC showed significantly different concentrations (2478, 565, 422 and 150 ppm) of AZA in the methanolic, hexanic, oily and aqueous extracts. The bioassay to determine the insecticidal effect and the phytotoxicity of the extracts consisted of exposing 10 nymphs of.4. gossypii to leaves of I.coccinea treated with each extract to doses of 0.01, 0.1 and 0.2 mg f AZA in 5 cm², and a control with water, with three replicates. Mortality was measured at 24, 48 and 72 h. Only the oily extract produced lesions in 35 % of the treated leaf area with moderate damage and level 5 phytotoxicity in I.coccinea. Significant differences were found in the mortality of A. gossypii per type of extract, time and dose, as well as in the interactions dose time and dose type of extract. The extract with the highest insecticide potential was the methanolic (0.2 mg AZA), with 100 % mortality at 48 and 72 h (p≤0.0001). The simultaneous application of methanol and cold press extracts more AZA from the seed of A. indica, promoting a higher insecticidal activity.

Keywords : methanolic extract; neem; tetranortriterpenoid.

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