ABSTRACT Leaf-cutting ants are the main pests in forest plantations. The most commonly used chemical control for the ants is toxic bait. However, the active ingredients in these baits have been restricted by forest certification organizations, justifying the search for new active compounds to control these insects. Thus, this work aimed to evaluate the formicidal activity of alkaloid fractions from the roots, stems, branches and leaves of Psychotria hastisepala and Psychotria leiocarpa (Rubiaceae) against Atta sexdens Forel, 1908 (Hymenoptera: Formicidae). The alkaloid fractions were obtained from the crude methanolic extracts of P. hastisepala and P. leiocarpa by the acid-base extraction method employing liquid-liquid partitions. The fractions, previously solubilized in propanone, were applied topically to the pronotum of worker ants. Bioassays were conducted in a completely randomized design, with six replicates of each treatment and 10 ants per replicate. Insect survival was assessed daily for 21 days. The median lethal time was estimated by Weibull models. The root fractions from P. hastisepala presented the highest toxicity, followed by those from the branches, stems and leaves. Among fractions from P. hastisepala roots, the most toxic were a fraction that apparently is rich in lipophilic compounds and nonbasic alkaloids and a fraction that is likely rich in quaternary benzophenanthridine alkaloids, protopine alkaloids and tertiary bases. Psychotria leiocarpa fractions were not toxic to this insect. Psychotria hastisepala is potentially useful for the development of new products for A. sexdens control.

RESUMO A lagarta do cartucho (LCM) (Spodoptera frugiperda) é um inseto polífago que causa danos em várias culturas. Inseticidas químicos sintéticos e plantas geneticamente modificadas são os métodos mais comumente empregados para o seu controle. Entretanto, existem muitos relatos da seleção de populações resistentes, o que justifica a busca por novas moléculas para o controle de S. frugiperda. O objetivo desse trabalho foi avaliar a toxicidade do óleo essencial de capim limão (Cymbopogon flexuosus) (OECL) e seu componente majoritário, citral, para LCM. Adicionalmente, a atividade anticolinestarase do OECL e do citral foram avaliadas usando a acetilcolinestarase (AChE) de Electrophorus electricus. OECL foi tóxico para LCM, quando incorporado em dieta artificial (CL50 = 1,35 mg mL-1), nas mais altas concentrações testadas, o tempo letal mediano (TL50) foi de 18,85 h. Os componentes majoritários do OECL foram identificados por cromatografia gasosa acoplada a espectometria de massas. Citral, o composto mais abundante, foi empregado em bioensaios com LCM. A atividade inseticida do citral foi estatisticamente similar àquela do OECL, demonstrando que o citral é responsável pela atividade inseticida do OECL. A inibição da AChE foi mensurada, sendo os valores de concentração inibitória media (CI50) encontrados para o OECL e citral, 650 e 405 vezes maiores, respectivamente, do que o detectado para o controle positivo, o inseticida metomil, sugerindo seletividade para organismo não-alvo. Os resultados encontrados tornam o citral e C. flexuosus promissores para serem empregados no desenvolvimento de novos produtos para o controle de S. frugiperda.

ABSTRACT Fall armyworm (FAW) (Spodoptera frugiperda) is a polyphagous insect responsible for damage to several crops. Synthetic chemical insecticides and genetically modified plants are the most commonly used methods for FAW control. However, the selection of resistant populations has been reported in several studies, justifying the search for new molecules to be used in the control of S. frugiperda. The aim of the present study was to evaluate the toxicity of lemongrass (Cymbopogon flexuosus) essential oil (LEO) and its major component (citral) in relation to FAW. Additionally, the anticholinesterase activity of LEO and citral was evaluated using acetylcholinesterase (AChE) from Electrophorus electricus. The LEO was toxic to FAW when added to an artificial diet (LC50 = 1.35 mg mL-1) at the highest concentrations tested, and the median lethal time (LT50) was 18.85 h. Major components of LEO were identified by gas chromatography-mass spectrometry, and citral, the most abundant component, was used in FAW bioassays. The insecticidal activity of citral was statistically similar to that of LEO, demonstrating that citral was responsible for the insecticidal activity of LEO. Inhibition of AChE was measured, and the mean inhibitory concentration (IC50) values for LEO and citral were 650- and 405-fold higher, respectively, than that verified for the positive control (methomyl insecticide), suggesting selectivity for non-target organisms. Based on these results, citral and C. flexuosus have the potential to be applied in the development of new products for the control of S. frugiperda.

Objetivou-se, com o presente trabalho, verificar o efeito do extrato metanólico de Coffea racemosa Lour., espécie silvestre de cafeeiro portadora de resistência a uma das principais pragas da cultura cafeeira, o bicho-mineiro. Inicialmente, o extrato metanólico das folhas de C. racemosa foi pulverizado em mudas de cafeeiro Coffea arabica cv. Catuaí, em casa-de-vegetação, as quais foram expostas a adultos de L. coffeella para o teste de oviposição com chance de escolha. Observou-se que as plantas tratadas foram menos preferidas para oviposição. A seguir, realizou-se o teste de efeito ovicida, no qual mudas de C. arabica contendo ovos do bicho-mineiro foram pulverizadas com o mesmo extrato. Os experimentos foram conduzidos em delineamento inteiramente casualizado com cinco repetições. Verificou-se redução significativa na eclosão de larvas, e segundo análise por microscopia eletrônica de varredura, os ovos não viáveis apresentaram anomalias nas superfícies externas. Entretanto, os adultos provenientes de ovos tratados não foram afetados na percentagem de emergência, razão sexual e oviposição. Os resultados obtidos demonstram que C. racemosa apresenta-se como uma alternativa promissora ao controle do bicho-mineiro, necessitando, no entanto, de novos estudos para isolamento e identificação das substâncias bioativas.

The objective of this study was to evaluate the effect of Coffea racemosa Lour. methanolic extract , a wild coffee specie that presents resistance against the coffee leaf-miner, a major pest of coffee crop. The methanol extract of C. racemosa leaves was sprayed on coffee seedlings, Coffea arabica cv. Catuaí, in greenhouse, which were exposed to adults of L. coffeella for oviposition in free choice test. Plants treated were less preferred for oviposition. An ovicidal assay was carried out by spraying the methanol extract on C. arabica seedlings containing L. coffeela eggs on their leaves. The experiments were conducted in a completely randomized design with five replicates. Larvae hatching out from treated eggs were significantly reduced by the extract and non viable eggs presented some anomalies on their external surfaces according to analyses by scanning electron microscopy. However, the adults derived from treated eggs did not have the percentage of emergence, sex ratio and oviposition affected by the treatment. The results show that C. racemosa presents as a promising alternative to control the coffee leaf-miner, being necessary new studies to isolate and caracterize the bioactive substances against this pest.

Conduziu-se este trabalho, com o objetivo de quantificar taninos condensados presentes nas cascas do caule de Ochroma pyramidalis (Bombacaceae), Schinus terebinthifolius (Anacardiaceae), Enterolobium contortisiliquum (Fabaceae) e Peltophorum dubium (Fabaceae) e verificar o efeito de frações tânicas dessas espécies sobre parâmetros biológicos e nutricionais de S. frugiperda. A partir das cascas das espécies vegetais se prepararam extratos, dos quais alíquotas foram tomadas para a quantificação dos taninos. Em seguida, os extratos foram submetidos a fracionamento para a obtenção das frações tânicas, que foram incorporadas à dieta artificial e oferecidas para lagartas de S. frugiperda. Todas as espécies vegetais estudadas apresentaram taninos condensados, sendo que S. terebinthifolius apresentou menor quantidade desses compostos. A fração tânica de P. dubium causou redução no peso das lagartas e pupas, diminuição na sobrevivência de S. frugiperda durante as fases larval e pupal, e acarretou menor consumo alimentar, além de prolongar a duração das fases imaturas desse inseto. O tratamento com S. terebinthifolius causou redução na percentagem de sobrevivência, durante a fase de pupa. Pupas provenientes de lagartas que receberam tratamento com a fração de E. contortisiliquum tiveram aumento no seu período de desenvolvimento. Lagartas alimentadas com a fração proveniente de P. dubium apresentaram a menor taxa de crescimento relativo (RGR), menor eficiência de conversão do alimento digerido (ECD) e maior custo metabólico (CM). A digestibilidade aproximada (AD) foi maior para os tratamentos com as frações tânicas de P. dubium e S. terebinthifolius.

The objective of this study was to quantify condensed tannins present in the stem bark of Ochroma pyramidalis (Bombacaceae), Schinus terebinthifolius (Anacardiaceae), Enterolobium contortisiliquum (Fabaceae) and Peltophorum dubium (Fabaceae) and to verify the effect of tannic fractions of these species on biological and nutritional parameters of S. frugiperda. Extracts were prepared from the barks of the plant species and aliquots were taken from them to quantify the tannins. The extracts were then submitted to fractionation to obtain the tannic fractions, which ones were incorporated into an artificial diet and offered to the larvae of S. frugiperda. All the studied species showed condensed tannins, and S. terebinthifolius showed the lowest amount of these compounds. The tannin fraction of P. dubium caused a reduction in the weight of larvae and pupae, decreased the survival of S. frugiperda during the larval and pupal stages and led to a reduction of intake, beyond to extend the duration of immature stages of this insect. The treatment with S. terebinthifolius caused a reduction in the survival percentage during the pupal stage. Pupae from larvae that received the treatment with the fraction of E. contortisiliquum had an increase in its development period stage. Larvae fed with the fraction from P. dubium showed the lowest relative growth rate (RGR), lower efficiency of conversion of ingested food (ECI) and a higher metabolic cost (CM). The approximate digestibility (AD) was higher for the treatments with tannic fractions of P. dubium and S. terebinthifolius.

Estudou-se a influência de extratos vegetais no crescimento, in vitro, de plântulas de Rosa x hybrida, objetivando o desenvolvimento de novos reguladores vegetais para a propagação dessa planta ornamental. Extratos metanólicos de Saintpaulia ionantha Wendl. (folhas), Hibiscus rosa-sinensis L. (folhas) e Bougainvillea spectabilis Wild. (folhas e flores) foram obtidos nas concentrações de 150 e 300 mg.L-1. Na ocasião de preparo do extrato todas as plantas se encontravam no período de floração. O experimento foi realizado em delineamento inteiramente casualizado com dez tratamentos e quatro repetições. Dois desses tratamentos foram utilizados como controle: meio de cultura com e sem BAP (6-benzilaminopurina). As variáveis analisadas foram: número e comprimento de brotos, número e comprimento de raízes, e número de folhas por broto. Quanto à variável número de brotos, todos os extratos testados se comportaram como o controle sem o BAP. No que diz respeito ao número e comprimento de raízes, apenas o extrato das folhas de H. rosa-sinensis na concentração de 300 mg.L-1 se mostrou diferente do controle sem o BAP, com valores estatisticamente iguais ao do controle com BAP. Excetuando-se o extrato de H. rosa-sinensis, todos reduziram o número de folhas por broto. Embora os efeitos observados não tenham sido tão pronunciados quanto os causados pelo BAP, os resultados indicam a presença de fitormônios nos extratos estudados.

This work aimed to study the influence of plant extracts on the in vitro growth of Rosa x hybrida plantlets, to contribute to the development of new plant growth regulators to propagate such ornamental plant. Methanolic extracts of Saintpaulia ionantha Wendl. (leaves), Hibiscus rosa-sinensis L. (leaves) and Bougainvillea spectabilis Wild. (leaves and flowers) were employed at 150 and 300 mg.L-1. Flowering plants were used to obtain the extracts. The experiment was carried out in a randomized design, with ten treatments and four repetitions. Culture medium with and without BAP (6-benzylaminopurine) were used as controls. The analyzed variables were shoot number and length, root number and length, and leaves per shoot. Regarding shoot number, all extracts were statistically identical to the control without BAP. When root number and length were taken into account, only the extract of H. rosa-sinensis leaves at 300 mg.L-1 differed from the control without BAP, with values statistically identical to the control with BAP. Except for the H. rosa-sinensis extract, all the others reduced the number of leaves per shoot. Although the observed effects were not as pronounced as those obtained with BAP, these results indicate the presence of plant growth regulators in the studied extracts.