Busca de substâncias de Trichilia pallida e Trichilia pallens (Meliaceae) com atividade sobre a traça-do-tomateiro Tuta absoluta (Meyrick) (Lep.: Gelechiidae). / Searching Trichilia pallida and Trichilia pallens (meliaceae)for substances with insecticidal activity against the tomato leafminer Tuta absoluta (Meyrick) (Lep.: Gelechiidae).

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Organic and aqueous extracts of the Meliaceae Trichilia pallida and Trichilia pallens were produced for the isolation and identification of substances with insecticidal activity against the tomato leafminer Tuta absoluta. Leaf and twig freeze-dried aqueous extracts (FDA) of both Trichilia species were resuspended in water at a concentration of 3% and sprayed over tomato folioles with the aid of a mini-atomizer, which were infested with newly-hatched larvae. Larval mortality at 5 and 10 days after infestation (DAI) were higher for leaf extracts of both Trichilia species. In a second set of experiments, 1% leaf extracts of T. pallida and T. pallens were produced by maceration in hexane (HEX), dichloromethane (DIC) and methanol (MET), and tested as described above using acetone and water as control. DIC extracts were the most promising as a source of substances with insecticidal activity against larvae of T. absoluta. DIC leaf extracts of T. pallida and T. pallens were further processed and subjected to partition assays, producing fractions in HEX, MET, ethyl acetate (ETA), n-butanol (NBU) and water (WA). After testing, 0.15% ETA and 0.1% WA fractions obtained from the partition assay of DIC extracts of T. pallida and T. pallens, respectively, showed the highest insecticidal activity against T. absoluta. Leaf extracts of T. pallida in dichloromethane (DIC) yielded six compounds, the triterpenes 24-methylene-cycloarta-3β-ol (TRIT-1), 24-methylene-cycloarta-3β-26- diol (TRIT-2) and cycloarta-23-en-3β,25-diol (TRIT-3) and the steroids 24-methylene-3,22-dihidroxi-cholesterol (EST-1), 24-methylenecholesterol (EST-2) and 24-methylene-3β,4β,22-trihidroxi-cholesterol (EST-3); the limonoid gedunine (LIM) was obtained from fruits of this plant. The insecticidal activity of all these substances against T. absoluta larvae were tested at 0.1% as previously described, assessing larval mortality at 5 and 9 DAI, larval and pupal developmental time and survivorship, pupal weight and adult malformation. TRIT-1, EST-1 and LIM were the most effective against T. absoluta by arresting larval development and reducing larval survivorship.

ASSUNTO(S)

rutales pragas de plantas tomato leafminer phytosanitary fitossanidade pesticide producing plants plantas produtoras de pesticidas tomate meliacea pest of plants meliaceae traças rutales

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