Bioactivity of Schinus molle L. and Schinus terebinthifolia Raddi. Essential Oils on Anticarsia gemmatalis (Hübner 1818)

Abstract Anticarsia gemmatalis is one of the main pests of the soybean crop, being controlled mainly with agrochemicals. The environmental and health risks, as well as the development of resistance by the pests, has led to the search for alternative control measures, aiming to use more eco-friendly procedures. The objective of this research was to evaluate the chemical composition and the bioactivity of Schinus molle and Schinus terebinthifolia essential oils (EOs) on A. gemmatalis. The major compound in both EOs was α-pinene (60.04 wt.% for S. molle and 38.49 wt.% for S. terebinthifolia). Bioassays were carried out with third instar larvae, with five replicates and each replicate with ten larvae, totaling 50 larvae per treatment. The oils were incorporated in the artificial diet (0.1, 0.5, 1.0, 1.5, and 2.0% v/v). The controls were: water, Tween-80® 0.5% v/v, and novaluron 0.075% v/v. According to the Probit method, the S. terebinthifolia EO presented a LC50 of 1.74% v/v (1.58-1.97% v/v); it was not possible to determine the LC50 for the S. molle EO. The mortality percentage after 24 and 48 h was 52% and 30% at 2.0% v/v for S. terebinthifolia and S. molle oil, respectively. After 72 h, the mortality rate for S. molle EO have not changed; for S. terebinthifolia EO it increased to 70%; the larvae treated with the chemical control (synthetic insecticide) had a mortality of 100%.

Biological Activity of Piper aduncum extracts on Anticarsia gemmatalis (Hübner) (Lepidoptera: Erebidae) and Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

ABSTRACT Piper aduncum found naturally in the Amazon and southeastern Brazil, is known for its secondary metabolites that have activity on insects. Anticarsia gemmatalis and Spodoptera frugiperda are among the major insect pests associated with agricultural production. This research evaluated the biological activity of hexane, ethyl acetate, and ethanol extracts of P. aduncum leaves on mortality and duration of larval and pupal periods, as well as weight, width, and length of A. gemmatalis and S. frugiperda pupae. The mortality of A. gemmatalis larvae in trials with P. aduncum extracts were 93.3% (hexane) and 90% (ethyl acetate), estimating LC50 of 6.35 and 5.79 mg/mL, respectively. Mortality in S. frugiperda submitted to the hexane extract ranged from 3.33% to 96.66% (LC50 of 8.22 mg/mL). The ethanol extract induced low mortality (3.33% to 23.33%). The P. aduncum extracts did not affect the development of S. frugiperda pupae. In A. gemmatalis differences in weight and length occurred. The chemical characterization was by GC-MS, which revealed that the major constituent in the hexane extract of P. aduncum was apiol (90.7%). P. aduncum extracts are important and promising components to manage A. gemmatalis and S. frugiperda, which cause extensive production losses.

Insecticide resistance in populations of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), from the state of Pernambuco, Brazil

The diamondback moth Plutella xylostella (L.) has a great economic importance in Brassicaceae crops in many parts of the world. Recurrent infestations of this pest in growing areas of Pernambuco state, Brazil, have led farmers to frequently spray their crops with insecticides. However, control failures by several insecticides have been alleged by farmers. The objective of this study was to check whether resistance to insecticides could explain these control failures in P. xylostella. Populations of P. xylostella from Pernambuco were collected between January and April 2009. The resistance ratios of P. xylostella populations were compared among five different active ingredients: abamectin, methomyl, lufenuron, indoxacarb, and diafenthiuron by leaf dipping bioassays using foliar discs of kale leaves. Mortality data were submitted to probit analysis. The P. xylostella populations showed variable response and significant resistance to one or more insecticides. The population from Bezerros County exhibited the highest resistance ratios to indoxacarb (25.3 times), abamectin (61.7 times), and lufenuron (705.2 times), when compared to the reference population. The populations from Bonito and Jupi Counties were 33.0 and 12.0 times more resistant to lufenuron and abamectin, respectively, when compared with the reference population. Resistance to methomyl was the least common, but not less important, in at least four populations. These results indicated that control failures were associated with resistance by some of the evaluated insecticides, reinforcing the need for resistance management in areas of the state of Pernambuco.

Phagodeterrence by Quassia amara (Simaroubaceae) wood extract fractions on Hypsipyla grandella (Lepidoptera: Pyralidae) larvae

In Latin America and the Caribbean, precious wood species like mahoganies (Swietenia spp.) and cedars (Cedrela spp.) are seriously injured by the mahogany shootborer, Hypsipyla grandella (Zeller) (Lepidoptera: Pyralidae) larva, which bores into the main shoot of trees. In previous experiments focused on searching for a preventive method for managing this pest, a wood extract of bitterwood, Quassia amara L. ex Blom (Simaroubaceae) had been shown to cause phagodeterrence to larvae. Therefore, three fractions (water, methanol and diethyl ether) of a wood extract were tested for their phagodeterrence to larvae, by means of laboratory and greenhouse trials. Phagodeterrence was assessed by determining their effect on foliage consumption, mortality and signs of damage (number of orifices, sawdust piles, fallen shoots, number of tunnels and tunnel length) caused by larvae on Spanish cedar (C. odorata). Both the methanol and diethyl ether fractions caused phagodeterrence, by strongly reducing foliage consumption and signs of damage, while not causing larval mortality. The lowest concentration at which phagodeterrence was detected for the methanol fraction corresponded to 0.0625%, which is equivalent to a 1.0% of the bitterwood crude extract. However, results with the diethyl ether fraction were unsatisfactory, as none of the treatments differed from the solvent, possibly because of an adverse effect of the solvent on foliar tissues. Phagodeterrent principles from Q. amara derivatives may play an important role in dealing with H. grandella if they are complemented with other integrated pest management preventative tactics. Rev. Biol. Trop. 59 (1): 487-499. Epub 2011 March 01.

En América Latina y el Caribe, algunas especies que son fuente de maderas preciosas, como las caobas (Swietenia spp.) y cedros (Cedrela spp.), son seriamente dañadas por la larva de Hypsipyla grandella, la cual barrena el brote principal de los árboles. En experimentos previos orientados hacia la búsqueda de un método preventivo para manejar esta plaga, un extracto de la madera de hombre grande, Quassia amara (Simaroubaceae), había demostrado causar fagodisuasión a la larva. Por tanto, tres fracciones de un extracto de la madera de dicho árbol (agua, metanol y éter dietílico) fueron evaluadas en cuanto a su efecto fagodisuasivo sobre las larvas, mediante experimentos de laboratorio e invernadero. Dicho efecto se determinó según el consumo de follaje, la mortalidad y los signos de daño (número de orificios, montículos, brotes caídos, número y longitud de túneles) causados por las larvas en arbolitos de cedro amargo (C. odorata). Tanto la fracción de metanol como la de éter dietílico causaron fagodisuasión, pues redujeron fuertemente el consumo de follaje y los signos de daño, sin matar las larvas. La menor concentración de la fracción metanólica a la cual se detectó fagodisuasión correspondió a 0.0625%, la cual equivale al 1.0% del extracto crudo de hombre grande. Por su parte, los resultados con la fracción de éter dietílico fueron insatisfactorios, ya que ninguna de las concentraciones difirió del disolvente, quizás debido a un efecto adverso del mismo sobre los tejidos foliares. Los principios fagodisuasivos de los derivados Q. amara podrían jugar un papel importante para manejar a H. grandella, si fueran complementados con otras tácticas preventivas de manejo integrado de plagas.

Plant Extracts as an Alternative to Control Leucoptera coffeella (Guérin-Mèneville) (Lepidoptera: Lyonetiidae)

We evaluated the effects of crude extracts from the plantain Plantago lanceolata and the bitter gourd Momordica charantia on the oviposition preference and development of the coffee leaf miner Leucoptera coffeella Guérin-Mèneville & Perrottet under laboratory and/or greenhouse conditions. The ovicidal effects of these extracts were also studied in a greenhouse. Plantago lanceolata and M. charantia extracts also underwent fractionation directed by oviposition tests with the coffee leaf miner. The extracts of both plants reduced L. coffeella oviposition and egg hatching, apparently as a result of action of plant metabolites on the embryo. Adults originating from eggs treated with the extracts exhibited similar survival rates, but a higher female/male ratio. Fecundity was reduced for females obtained from eggs treated with the M. charantia extract. Partial chemical analysis indicated that both extracts produced polar fractions that reduced the oviposition of L. coffeella on coffee leaves under laboratory conditions. The extracts of P. lanceolata and M. charantia have potential for use in the development of new products to control the coffee leaf miner.

Do different casein concentrations increase the adverse effect of rutin on the biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)?

The flavonoid rutin is recognized as playing an important role in the protection of plants against lepidopterans. Bioassays with this compound are generally carried out using artificial diets. Proteins of high energy value, such as casein, are important ingredients of insect artificial diets as a source of essential amino acids. However, such proteins can generally increase the allelochemical activity. Our objective was to evaluate the effects of rutin on larvae of the velvetbean caterpillar Anticarsia gemmatalis Hübner by incorporating this allelochemical into diets with different concentrations of casein. Three casein concentrations (0, 7 g, or 14 g) combined with none, 0.65 percent, or 1.30 percent of rutin were added to the rearing diet and offered to the larvae from hatching to pupation. Rutin negatively affected larval development, the amount of food consumed, and pupal weight of A. gemmatalis. These negative effects were clearly seen in insects fed on diets with 7 g of casein to which any concentration of rutin was added. The effects of rutin when added to the diets without casein were stronger than in diets containing a suitable amount of casein (14 g). The greater negative effects of rutin in diets containing suboptimal concentrations of casein indicate that casein can increase the effects of rutin only when the diets are nutritionally unsuitable for insect development.

Efeito de genótipos de tomateiro e de extratos aquosos de folhas de Melia azedarach e de sementes de Azadirachta indica sobre Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) / Effects of tomato genotypes and aqueous extracts of Melia azedarach leaves and Azadirachta indica seeds on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Insecticide plants are an important tool among the new alternatives for pest control in IPM systems because they reduce the use of synthetic insecticides, preserving human health and the environment. We investigated the effects of aqueous extracts of Melia azedarach leaves and Azadirachta indica seeds and three tomato genotypes, 'Santa Clara', 'IPA-5' - Solanum lycopersicum (= Lycopersicon esculentum Mill), and LA444-1 - S. peruvianum (= L. peruvianum), on the development, reproduction and longevity of the tomato pinworm Tuta absoluta (Meyrick), under laboratory conditions. The trials were set up in a completely randomized design, with nine treatments [three genotypes x two extracts (M. azedarach and A. indica) and control]. The replication consisted on five tubes, each with three newly hatched larvae, totalizing 90 individuals per treatment. The larvae were fed with tomato leaves treated with aqueous extracts at 0.1 percent concentration or distilled water (control) and daily observed until adults' emergence. Larval and pupal development and mortality, pupal weight, longevity and fecundity were evaluated. The accession LA444-1 negatively affected the development and reproduction of T. absoluta; the tomato pinworm had similar development and reproduction on 'IPA-5' and 'Santa Clara' (the susceptible control). The association of resistant tomato genotypes and extracts of M. azedarach leaves and neem seeds did not result in synergistic or antagonistic effects on T. absoluta.

Fagodisuasión de un extracto de ruda (Ruta chalepensis, Rutaceae) y sus particiones sobre larvas de Hypsipyla grandella (Lepidoptera: Pyralidae)

Phagodeterrence by a crude extract of common rue (Ruta chalepensis, Rutaceae) and its partitions on Hypsipyla grandella (Lepidoptera: Pyralidae) larvae. Hypsipyla grandella (Zeller) larva is maybe the main forest pest in Latin America and the Caribbean, as it bores into the main shoot of trees providing precious woods, such as mahoganies (Swietenia spp.) and cedars (Cedrela spp.). In the search for a preventative method for managing it, the crude leaf extract of common rue (Ruta chalepensis L.), as well as four partitions thereof (water, hexane, dichlorometane, and ethyl acetate), were tested for phagodeterrence. Laboratory bioassays involved increasing concentrations of the crude extract (0.1, 0.32, 1.0, 3.20 and 10.0%w/v) as well as each one of the partitions (in accordance to the yield obtained from the partitioning process), plus rutin, a flavone glycosid. A randomized complete block design, with four replicates, was used. H. grandella instar III larvae were exposed for 24 h to cedar (Cedrela odorata) leaf discs dipped into the respective treatment, after which disc consumption was measured. Strong phagodeterrence was detected at concentrations as low as 0.32 and 0.074%w/v for the crude extract and the hexane partitions, respectively; the ethyl acetate (0.24%w/v) and the water partition (for all of its concentrations), as well as the rutin (starting at 0.064%w/v), caused phagodeterrence, too. Moreover, the crude extract was submitted to a phytochemical screening by means of a number of qualitative tests, to determine possible metabolites causing phagodeterrence, the most important being alkaloids, triterpenes, coumarins and rutin. A particular phytochemical screening was carried out for the hexane partition, which was the most active. Rev. Biol. Trop. 58 (1): 1-14. Epub 2010 March 01.

La larva de Hypsipyla grandella (Zeller) es quizás la principal plaga forestal en América Latina y el Caribe, por perforar el brote principal de árboles de maderas reciosas, como caobas (Swietenia spp.) y cedros (Cedrela spp.). En la búsqueda de un método preventivo para su manejo, se estudió la actividad fagodisuasiva del extracto crudo y de cuatro particiones fitoquímicas (agua, hexano, diclorometano y acetato de etilo) del follaje de ruda (Ruta chalepensis L.). Se realizaron bioensayos de laboratorio con concentraciones crecientes del extracto crudo (0.1; 0.32; 1.0; 3.20 y 10.0%m/v) y con cada una de las particiones (según el rendimiento del proceso de particionamiento), así como con el glicósido flavónico rutina. Para ello se empleó un diseño de bloques completamente al azar, con cuatro repeticiones y se expusieron larvas de instar III de H. grandella a discos de cedro (Cedrela odorata) impregnados con el respectivo tratamiento, por 24h. Se midió el porcentaje de consumo de cada disco. Hubo un fuerte efecto fagodisuasivo en el extracto crudo y en la partición hexano, a concentraciones tan bajas como 0.32% y 0.074% m/v, respectivamente; las particiones de acetato de etilo (0.24%m/v) y la acuosa (en todas sus concentraciones), así como la rutina (a partir del 0.064%m/v) también causaron fagodisuasión. Además, se realizó un tamizaje fitoquímico del extracto crudo, utilizando varias pruebas cualitativas para detectar la presencia de los principales grupos de metabolitos secundarios, entre los cuales los más importantes fueron alcaloides, triterpenos, cumarinas y la rutina. Asimismo, se realizó una marcha fitoquímica a la partición hexano, por ser la más activa.

Actividad fagodisuasiva y sistémica de una formulación derivada de un extracto de ruda (Ruta chalepensis, Rutaceae) sobre larvas de Hypsipyla grandella (Lepidoptera: Pyralidae)

Phagodeterrent and systemic activity of a fomulation derived from an extract of common rue (Ruta chalepensis, Rutaceae) on Hypsipyla grandella (Lepidoptera: Pyralidae) larvae. A key neotropical pest of mahoganies (Swietenia spp.) and cedars (Cedrela spp.), the larva of Hypsipyla grandella (Zeller) commonly bores into the main shoot of these valuable timber species, causing forking of the stems. Therefore, it would be desirable to count upon a phagodeterrent and systemic product which could readily protect young tissues. Since crude extracts of common rue foliage (Ruta chalepensis L.) have phagodeterrent activity on H. grandella larva, a product was formulated by combining such an extract with a number of coadjuvants, and was assessed on 75-100cm tall Spanish cedar (Cedrela odorata L.) trees, inside a greenhouse. A completely randomized design was used, with 10 trees per each one of the following treatments: the formulated product, an absolute control (distilled water), a relative control (carbofuran, 1%m/v in water), and the relative control without the crude extract. Number of attacks to the main shoot, fallen leaves and frass piles were recorded, as well as tunnel length. Regarding these variables, the formulated product provided excellent protection to treated trees, with only 0.1 attacks to the main shoot, on the average, at the end of the evaluation period. Likewise, when the systemic activity of the crude extract was assessed, substances present in it were able to translocate and get assimilated by the trees, thereafter causing phagodeterrence to larvae. Finally, an espectrophotometry analysis (performed at a wavelength of 355nm) allowed us to determine the concentration (403±1mg/l) and percentage (0.40%) of the flavonoid rutin in the crude extract, which eventually may be used as an analytical marker compound, should an industrial formulation be developed. Rev. Biol. Trop. 58 (1): 15-29. Epub 2010 March 01.

Para el manejo de Hypsipyla grandella (Zeller), cuya larva barrena el brote principal de caobas (Swietenia spp.) y cedros (Cedrela spp.), sería deseable contar con un producto fagodisuasivo y con buena actividad sistémica, para que proteja rápidamente los tejidos jóvenes. Por tanto, conociendo que un extracto crudo del follaje de ruda (Ruta chalepensis L.) posee actividad fagodisuasiva contra dicho insecto, se formuló un producto combinando dicho extracto con varios coadyuvantes, y se evaluó en árboles de cedro amargo (Cedrela odorata L.) de 75- 100cm de altura, en un invernadero. Se utilizó un diseño completamente al azar, con 10 árboles por cada tratamiento, los que correspondieron al producto formulado, a un testigo absoluto (agua destilada), un testigo relativo (carbofurán al 1%m/v en agua) y el testigo relativo a la formulación sin el extracto crudo. Las variables medidas fueron los ataques al brote principal, el número de hojas caídas, el número de montículos y la longitud de los túneles. Para dichas variables, el producto formulado aportó excelente protección a los árboles tratados, con apenas 0.1 ataques al brote principal, en promedio, al final del período de evaluación. Asimismo, al evaluar la actividad sistémica del extracto, las sustancias presentes en él pudieron desplazarse y ser asimiladas por los árboles, causando fagodisuasión en las larvas. Finalmente, el análisis espectrofotométrico (a una longitud de onda de 355nm) permitió determinar la concentración (403±1mg/l) y el porcentaje (0.40%) del flavonoide rutina en el extracto crudo, lo cual eventualmente podría utilizarse como un compuesto marcador analítico, si llegara a desarrollarse una formulación industrial.

Bioatividade de moléculas isoladas de Trichilia pallida Swartz (Meliaceae) sobre Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) / Bioactivity of Trichilia pallida Swartz (Meliaceae) derived molecules on Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

A partir do extrato em diclorometano (DIC) de folhas e frutos de Trichilia pallida Swartz, objetivou-se fazer o isolamento e identificação de substâncias com atividade inseticida sobre a traça-do-tomateiro, Tuta absoluta (Meyrick). Do extrato em DIC de folhas de T. pallida foram isolados os triterpenos 24-metilenocicloarta-3β-ol (TRIT-1), 24-metilenocicloarta-3β-26-diol (TRIT-2) e cicloarta-23-eno-3β,25-diol (TRIT-3), os esteróides 24-metileno-3,22-diidroxicolesterol (EST-1), 24-metilenocolesterol (EST-2) e 24-metileno-3β,4β,22-triidroxicolesterol (EST-3), além do limonóide gedunina (LIM) obtido de frutos da planta. As substâncias foram dissolvidas em acetona e pulverizadas a 0,1% em folíolos de tomateiro infestados com lagartas recém-eclodidas. Foram avaliadas a mortalidade de lagartas aos quinto e nono dias após a infestação, duração e sobrevivência das fases de larva e pupa, peso de pupas e porcentagem de adultos deformados. TRIT-1, EST-1 e LIM foram as moléculas que apresentaram maior atividade sobre T. absoluta, alongando o desenvolvimento larval e reduzindo a sobrevivência dessa fase.

Dichloromethane (DIC) leaf and fruit extracts of Trichiliapallida Swartz were obtained for the isolation and identification of molecules with insecticidal activity against the tomato leafminer, Tuta absoluta (Meyrick). DIC leaf extracts of T. pallida yielded six compounds, the triterpenes 24-methylenecycloarta-3β-ol (TRIT-1), 24-methylenecycloarta-3β-26-diol (TRIT-2) and cycloarta-23-eno-3β,25-diol (TRIT-3), the sterols 24-methylene-3,22-dihydroxycholesterol (EST-1), 24-methylenecholesterol (EST-2) and 24-methylene-3β,4β,22-trihydroxycholesterol (EST-3), while the fruit extract yielded the limonoid gedunine (LIM). These molecules were dissolved in acetone and sprayed at 0.1% on tomato leaflets infested with newly-hatched larvae. Larval mortality at day 5 and 9 after infestation, larval and pupal developmental time and survival, pupal weight and adult malformation were evaluated. TRIT-1, EST-1 and LIM were the most effective against T. absoluta due to larval development arrestment and reduced larval survivorship.

Bacillus thuringiensis in caterpillars and associated materials collected from protected tropical forests in northwestern Costa Rica

Bacillus thuringiensis (Bt) synthesizes crystalline inclusions that are toxic to caterpillars (Lepidoptera) and other orders of invertebrates. Materials associated with 37 caterpillars from 16 species, collected while feeding on 15 different species of host plants in dry, cloud and rain forests located in the Area de Conservación Guanacaste in northwestern Costa Rica, were examined for the presence of Bt. From a total of 101 derived samples, 25 Bt isolates were cultured: 56% from host plant leaves, 8% from caterpillar guts and 36% from caterpillar fecal pellets. Bt was isolated from at least one sample in 38% of the systems constituted by the food plant, gut and fecal pellets corresponding to a single caterpillar. Four different morphologies of crystalline inclusions were observed, with bipyramidal and irregular crystal morphologies being the most prevalent.

Bacillus thuringiensis (Bt) sintetiza inclusiones cristalinas que resultan tóxicas para algunas larvas de lepidópteros y otros órdenes de invertebrados. Su presencia fue examinada en materiales asociados a 37 orugas de mariposas de 16 especies, las cuales fueron colectadas mientras se alimentaban en 15 especies diferentes de plantas hospederas en bosques secos, nubosos y húmedos localizados dentro del Área de Conservación Guanacaste (ACG) en el noroeste de Costa Rica. A partir de un total de 101 muestras se obtuvo 25 aislamientos de Bt: 56% a partir de material foliar de las plantas hospederas, 8% a partir del contenido intestinal de las larvas y 36% a partir de sus excrementos. Esta bacteria fue cultivada a partir de al menos uno de los 3 diferentes tipos de muestra asociados a una oruga particular (planta hospedera, intestino, excremento) en 38% de los casos posibles. En la colección de aislamientos obtenida se observaron cuatro morfologías de inclusiones cristalinas, siendo aquellas bipiramidales e irregulares las más prevalentes.

Effect of nitrogen on Passiflora suberosa L. (Passifloraceae) and consequences for larval performance and oviposition in Heliconius erato phyllis (Fabricius) (Lepidoptera: Nymphalidae)

Avaliou-se a influência do nitrogênio no crescimento e nas características morfológicas e nutricionais de Passiflora suberosa L. e as conseqüências no desempenho larval e oviposição de Heliconius erato phyllis (Fabricius). Foram utilizados três níveis de nitrogênio no solo (tratamentos) para o cultivo de P. suberosa: 0, 150 e 300 mg L-1. Larvas recém-eclodidas foram criadas em laboratório (25 ± 1ºC), individualmente, em ramos das plantas cultivadas em cada tratamento e fêmeas capturadas em campo foram submetidas a testes de escolha para oviposição. A taxa de crescimento, a área foliar e o comprimento dos internódios de P. suberosa aumentaram significativamente com a adição de nitrogênio. A dureza das folhas jovens nas plantas cultivadas sem adição de nitrogênio foi maior, as quais também apresentaram menor conteúdo de água. Houve maior concentração de nitrogênio e potássio nas plantas cultivadas com a adição de nitrogênio no solo. A qualidade nutricional do alimento expressa pela maior concentração de nitrogênio e água, diminuiu o tempo de desenvolvimento larval e aumentou o tamanho dos adultos, embora não tenha afetado a sobrevivência de forma significativa. As fêmeas escolheram os ramos das plantas fertilizadas para oviposição, o que foi positivamente relacionado com desempenho das larvas. Isto poderia explicar a manutenção desse comportamento, bem como a escolha por ramos maiores, registrado em estudos anteriores.

Resíduos de tiametoxam, aldicarbe e de seus metabólitos em folhas de cafeeiro e efeito no controle de Leucoptera coffeella (Guérin-Mèneville) (Lepidoptera: Lyonetiidae) / Residues of thiamethoxam, aldicarb and its metabolites in coffee leaves and effect on the Control of Leucoptera coffeella (Guérin-Mèneville) (Lepidoptera: Lyonetiidae)

O bicho-mineiro Leucoptera coffeella (Guérin-Mèneville), uma das pragas mais importantes da cafeicultura brasileira, é controlado principalmente com inseticidas. O objetivo deste trabalho foi estudar os resíduos e a translocação do inseticida tiametoxam em folhas de cafeeiros, bem como avaliar seu efeito no controle do bicho-mineiro, comparando-o com o aldicarbe, utilizado como padrão. Para isto, foi instalado um experimento no município de Garça, SP, no período de dezembro/2001 a agosto/2002. Os tratamentos utilizados foram: aldicarbe 150 G, nas doses de 2,25 e 4,50 g i.a./cova, tiametoxam 10 GR, nas doses de 0,15 e 0,30 g i.a./cova e testemunha (sem aplicação). Amostras de ramos foram colhidas em pré-contagem e aos 30, 60, 90, 120, 150, 180, 210 e 240 dias após a aplicação, em três alturas dos cafeeiros (terços inferior, médio e superior), avaliando-se a porcentagem de folhas minadas. As determinações de aldicarbe e seus metabólitos ativos, aldicarbe sulfoxido e sulfona, e os de tiametoxam foram feitas por cromatografia em fase gasosa usando-se detector de nitrogênio-fósforo e de espectrometria de massas, respectivamente. Os resultados indicaram translocação uniforme de ambos inseticidas nos três terços das plantas de café, quando aplicados no solo. Foi constatada também, a maior persistência do tiametoxam, cujos resíduos foram encontrados até oito meses após a aplicação, enquanto os metabólitos sulfóxido e sulfona foram encontrados entre quatro e seis meses após a aplicação. Foi observado controle do bicho-mineiro pela aplicação de ambos inseticidas.

Perspectives of digestive pest control with proteinase inhibitors that mainly affect the trypsin-like activity of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)

The present study describes the main characteristics of the proteolytic activities of the velvetbean caterpillar, Anticarsia gemmatalis Hübner, and their sensitivity to proteinase inhibitors and activators. Midguts of last instar larvae reared on an artificial diet were homogenized in 0.15 M NaCl and centrifuged at 14,000 g for 10 min at 4°C and the supernatants were used in enzymatic assays at 30°C, pH 10.0. Basal total proteolytic activity (azocasein hydrolysis) was 1.14 ± 0.15 absorbance variation min-1 mg protein-1, at 420 nm; basal trypsin-like activity (N-benzoyl-L-arginine-p-nitroanilide, BApNA, hydrolysis) was 0.217 ± 0.02 mmol p-nitroaniline min-1 mg protein-1. The maximum proteolytic activities were observed at pH 10.5 using azocasein and at pH 10.0 using BApNA, this pH being identical to the midgut pH of 10.0. The maximum trypsin-like activity occurred at 50°C, a temperature that reduces enzyme stability to 80 and 60 percent of the original, when pre-incubated for 5 and 30 min, respectively. Phenylmethylsulfonyl fluoride inhibited the proteolytic activities with an IC50 of 0.39 mM for azocasein hydrolysis and of 1.35 mM for BApNA hydrolysis. Benzamidine inhibited the hydrolysis with an IC50 of 0.69 and 0.076 mM for azocasein and BApNA, respectively. The absence of cysteine-proteinases is indicated by the fact that 2-mercaptoethanol and L-cysteine did not increase the rate of azocasein hydrolysis. These results demonstrate the presence of serine-proteinases and the predominance of trypsin-like activity in the midgut of Lepidoptera insects, now also detected in A. gemmatalis, and suggest this enzyme as a major target for pest control based on disruption of protein metabolism using proteinase inhibitors.

Bioefficacy and mode-of-action of some limonoids of salannin group from Azadirachta indica A. Juss and their role in a multicomponent system against lepidopteran larvae.

Biological activities of the salannin type of limonoids isolated from Azadirachta indica A. Juss were assessed using the gram pod borer Helicoverpa armigera (Hubner) and the tobacco armyworm Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae). Inhibition of larval growth was concomitant with reduced feeding by neonate and third instar larvae. All three compounds exhibited strong antifeedant activity in a choice leaf disc bioassay with 2.0, 2.3 and 2.8 microg/cm(2) of 3-O-acetyl salannol, salannol and salannin, respectively deterring feeding by 50% in S. litura larvae. In nutritional assays, all three compounds reduced growth and consumption when fed to larvae without any effect on efficiency of conversion of ingested food (ECI), suggesting antifeedant activity alone. No toxicity was observed nor was there any significant affect on nutritional indices following topical application, further suggesting specific action as feeding deterrents. When relative growth rates were plotted against relative consumption rates, growth efficiency of the H. armigera fed diet containing 3-O-acetyl salannol, salannol or salannin did not differ from that of starved control larvae (used as calibration curve), further confirming the specific antifeedant action of salannin type of limonoids. Where the three compounds were co-administered, no enhancement in activity was observed. Non-azadirachtin limonoids having structural similarities and explicitly similar modes of action, like feeding deterrence in the present case, have no potentiating effect in any combination.

Hormonal implication in Bracon-venom-induced paralysation of the host larva of Corcyra cephalonica (Lepidoptera: Pyralidae).

To facilitate oviposition, the ectoparasite Bracon hebetor, injects its venom, a paralysing toxin, to the host Corcyra larva that ultimately dies without showing any metamorphic change, even if allowed to remain unparasitised. At the initial stage of venom injection the rate of heartbeat of the host becomes abruptly high. This has been explained from the synergistic action of the substances of poison gland and calyx. The paralysed larvae subsequent to envenomization die within 240 hr. Application of hydroprene as single dose or with a booster dose after paralysation mostly increases the survival period considering heart beat as the index. The predicted value of survival period (714.4 hr), determined from a fitted equation obtained from the relationship between heart beat and survival period, indicates that a 100 microg treatment/larva with a booster dose of 50 microg/larva most effectively lengthens the period. It is concluded that the venom-induced physiological dysfunction of the immobilised larvae, as indicated in the rate of heart beat and survival period, though can be recovered to some extent after the application of juvenoids, there cannot occur any metamorphic change of these larvae. The parasitoid, therefore, succeeds in completing its development and metamorphosis by arresting the development of its host through an indirect hormonal suppression. The findings indicate an endocrine implication in host-parasite relationship in insect.

Antifeedant activity of aqueous extract of Gnidia glauca Gilg. and Toddalia asiatica Lam. on the gram pod borer, Helicoverpa armigera (Hbn).

Aqueous leaf extracts of two plants namely Gnidia glauca Gilg. and Toddalia asiatica Lam., have been screened for their antifeedant activity against the sixth instar larvae of Helicoverpa armigera (Hbn) by applying the aqueous leaf extracts at various concentrations viz., 0.2, 0.4, 0.6, 0.8 and 1.0 percent on young tomato leaves. The larval mortality of more than 50 percent at higher concentrations (0.8 and 1.0 percent) was observed in the aqueous extracts. Among the two aqueous leaf extracts tested, T. asiatica was found to show higher rate of mortality (86.1%) at 1.0 percent concentration. A reduction in the rate of food consumption and growth was observed in the larvae of H. armigera after 48 hours of treatments in both the aqueous extracts. Since this insect pest species have developed resistance and resurgence to synthetic insecticides, the only alternate is the usage of bio-pesticides for they are eco-friendly, pollution free and easily degradable.

Comparative toxicity of trivalent and hexavalent chromium compounds in fig moth Ephestia cautella (Walker).

Of the trivalent (CrSO4) and hexavalent (K2Cr2O7) chromium compounds, only the hexavalent produced significant deleterious effects on development and fertility of E. cautella, when eggs were reared on laboratory medium supplemented with different concentrations of these salts.