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RESUMO: A mosca branca Bemisia tabaci (Gennadius) biótipo B atualmente é uma das principais pragas do tomateiro. O uso de extratos botânicos no controle desse inseto é uma alternativa promissora, mas que ainda precisa ser melhor pesquisada. O presente trabalho teve como objetivo determinar a bioatividade de extratos aquosos de folhas de Melia azedarach L. e de ramos de Trichilia pallida Swartz, sobre a mosca branca Bemisia tabaci (Gennadius) biótipo B, criada em tomateiro. Foram realizados dois experimentos, avaliando-se a mortalidade e duração das fases de ovo e ninfa, após o tratamento da fase de ovo com os referidos extratos. No primeiro experimento, foram testadas as concentrações de 1 e 2% (p/v), acrescentando-se a concentração de 3% no segundo experimento. Em todos os tratamentos houve efeito ovicida, sendo o maior valor obtido com T. pallida a 3% (52,32%). Nos demais tratamentos, a mortalidade variou entre 16 e 37%. Os extratos aplicados sobre os ovos pouco afetaram a sobrevivência ninfal. Com exceção do tratamento com T. pallida a 2%, no primeiro experimento, em que a mortalidade ninfal foi de 26,42%, nos demais a mortalidade foi inferior a 16%. Em nenhum dos experimentos foi verificada alteração na duração dos períodos de incubação e ninfal.ABSTRACT: The silverleaf whitefly is today one of most important pests of tomato. The use of botanical extracts to control this insect is an interesting technique, but more research about it should be carried out. The objective of this work was to determine the bioactivity of aqueous extracts of Melia azedarach leaves and Trichilia pallida twigs on the silverleaf whitefly Bemisia tabaci (Gennadius) biotype B, reared on tomato. Extracts were applied to eggs, and mortality and duration of egg and nymphal stages were evaluated in two experiments. In the first experiment, extracts were tested at concentrations of 1 and 2% (w/v) and in the second experiment the concentration of 3% was added. The ovicidal effect was observed in all treatments. The highest value was obtained with the extract of T. pallida at 3% (52.32%). For the other treatments the mortality ranged between 16 and 37%. The extracts applied on eggs presented low effect on nymphs. With exception of T. pallida at 2%, in the first experiment, where the nymphal mortality was 26.42%, in the other treatments the values were lower than 16%. The duration of egg and nymph periods were not affected by the extracts.

-The whitefly is one of the most important tomato pests. Considering the difficulty for its control with synthetic insecticides, alternative methods have been studied. The objective of this study was to determine the insecticidal action (translaminar, sistemic and topical) of aqueous extract from neem seeds, Azadiracta indica A. Juss, on nymphs of silverleaf whitefly in tomato plants. Water was used as control in all experiments. To evaluate the translaminar action, the extract was applied at the concentrations of 0.5, 1 and 5% on the adaxial side of leaves infested with 7-day old nymphs. The sistemic action was evaluated applying 50 ml of extract, at the concentrations of 1, 5 and 10%, on soil of pots containing plants infested with nymphs (7 days old). As the mortality was 100% even in small concentration, this experiment was repeated twice with concentrations of 0.5, 1 and 5% with 30 and 20 ml of extract per pot. The topical effect was evaluated applying 0.2 µl of aqueous extract at the concentrations of 0.5, 1 and 5% on nymphs of third instar. This experiment was repeated with the concentrations of 0.1, 0.3 and 0.5%. The aqueous extract of neem showed insecticidal action by translaminar, sistemic and topical via on silverleaf whitefly. KEY WORDS: Insecta, Azadirachta indica, silverleaf whitefly, botanical extract, insecticidal plant RESUMO -A mosca-branca é considerada uma das principais pragas do tomateiro. Em razão da dificuldade de ser controlada com inseticidas sintéticos, têm-se buscado métodos alternativos de controle. Nesse trabalho, avaliou-se o efeito inseticida translaminar, sistêmico e de contato de extrato aquoso de sementes de nim, Azadiracta indica A. Juss, sobre ninfas de Bemisia tabaci (Genn.) biótipo B em tomateiro. Em todos os experimentos, utilizou-se água como testemunha. Para avaliar a ação translaminar, o extrato foi aplicado nas concentrações de 0,5; 1 e 5% na face adaxial de folhas infestadas com ninfas com sete dias de idade. Na avaliação da ação sistêmica, 50 ml do extrato, nas concentrações de 1; 5 e 10%, foram aplicados no solo de vasos com plantas infestadas com ninfas aos sete dias de idade. Como a mortalidade foi de 100%, mesmo na menor concentração, o experimento foi repetido mais duas vezes usando-se as concentrações de 0,5; 1 e 5% e 30 ml e 20 ml de extrato por vaso. A ação de contato foi avaliada aplicando-se 0,2 µl do extrato aquoso nas concentrações de 0,5; 1 e 5% sobre ninfas de terceiro ínstar. O experimento foi repetido com o extrato nas concentrações de 0,1; 0,3 e 0,5%. Conclui-se que o extrato aquoso de sementes de nim apresenta ação translaminar, sistêmica e de contato sobre a mosca-branca. PALAVRAS-CHAVE: Insecta, Azadiracta indica, extrato botânico, planta inseticida A mosca-branca Bemisia tabaci (Genn.), considerada uma das principais pragas do tomateiro, causa danos diretos pela sucção da seiva, injeção de toxinas e liberação de honeydew e indiretos pela formação de fumagina e transmissão de doenças viróticas (Ohnesorge & Rapp 1986, Yokomi et al. 1990).

RESUMOComparou-se a bioatividade de extratos aquosos a 3% (p/v) ABSTRACT EFFECT OF AQUEOUS EXTRACTS OF MELIACEOUS PLANTS ON BEMISIA TABACI B BIOTYPE ON TOMATO PLANTS (1)The objective of this research was to compare the effect of aqueous extracts of fresh fruits of Melia azedarach L., twigs of Trichilia pallida Swartz and seeds of zadirachta indica A. Juss, on eggs and nymphs of silverleaf whitefly Bemisia tabaci (Gennadius) B biotype reared on tomato plants. The extracts were tested at a concentration of 3%. In the first experiment, the extracts were applied on eggs and 3-day-old nymphs. Records were taken on mortality, duration of egg and nymphal stages. In the second experiment the extracts were applied on 3-day-old nymphs and records were taken on nymphal mortality, adult longevity and fecundity. The extracts of T. pallida were the most effective on eggs, followed by A. indica and M. azedarach. The extracts of A. indica were the most effective on nymphs followed by T. pallida and M. azedarach. In both experiments, the duration of egg and nymph stages, longevity and fecundity were not affected by the extracts.

The insecticidal effect of aqueous extract of twigs, leaves, fresh fruits and ripe fruits of Melia azedarach L. and twigs, leaves and cortex of Trichilia pallida Swartz was evaluated on eggs and nymphs of silverleaf whitefly Bemisia tabaci (Genn.) biotype B reared on tomato plants. The extracts were tested at the concentration of 3% (w/v). In the first experiment, the extracts were applied only on the egg stage. In the second experiment, the extracts were applied on eggs and 3-day old nymphs. Independent experiments were carried out for each plant species. The parameters evaluated were mortality and duration of egg and nymphal stages. Concerning M. azedarach, fresh fruits were the most effective plant structure followed by leaves and ripe fruits. For T. pallida, twigs were the most effective structure followed by leaves. The extract of twigs of M. azedarach and cortex of T. pallida did not show significant insecticidal activity. None of the plant extracts affected the duration of the immature stages.