Cláudio Augusto Gomes da Câmara

Allelopathy, an alternative tool to improve cropping systems. A review

Known since ancient times, the phenomenon of allelopathy has recently received greater attention from researchers and farmers worldwide. Crop failures and low yields caused by the reseeding, overseeding, crop rotation and replanting of fruit trees in orchards are believed to be caused by allelopathic activity. Moreover, the expensive and environmentally impacting herbicides for weed control have motivated studies directed at developing cheaper, environmentally-friendly alternatives. Despite the difficulties in separating chemical interference from other mechanisms, more modern approaches have produced consistent and conclusive data on this topic. The release and dynamics of allelochemicals in the soil are discussed herein. Examples of allelopathic crops, the allelochemicals produced and their uses in cropping systems are also presented along with current research trends regarding allelopathy.

Atividade inseticida de óleos essenciais e fixos sobre Callosobruchus maculatus (FABR., 1775) (Coleoptera: Bruchidae) em grãos de caupi [Vigna unguiculata (L.) WALP.]

O caruncho, Callosobruchus maculatus (Fabr.), e considerado a praga mais importante do caupi, Vigna unguiculata (L.) Walp., armazenado em regioes tropicais e subtropicais. Visando minimizar os efeitos indesejaveis dos inseticidas quimicos sinteticos, o controle dessa praga com oleos de origem vegetal vem se constituindo numa alternativa promissora, de baixo custo e segura para os aplicadores e consumidores. Foram testados os oleos essenciais [(Cymbopogon martini (Roxb.) J.F. Watson], Piper aduncum L., Piper hispidinervum C.DC., Melaleuca sp., Lippia gracillis Shauer) e fixos (Helianthus annuus L, Sesamum indicum L, Gossypium hirsutum L., Glycine max (L.) Merr. e Caryocar brasiliense Camb.), em graos de caupi, cv. Sempre Verde. Os oleos foram utilizados nas concentracoes 10, 20, 30, 40 e 50mL/20g, correspondendo a 0,5, 1,0, 1,5, 2,0 e 2,5 L/t e impregnados aos graos no interior de recipientes de plastico, com auxilio de pipetador automatico e agitados manualmente durante dois minutos. Parcelas de 20g de caupi foram infestadas com oito femeas de C. maculatus, com 0 a 48 h de idade. Cada oleo foi testado, separadamente, em delineamento inteiramente casualisado com seis repeticoes. Os oleos essenciais de C. martini, P. aduncum e L. gracillis causaram 100% de mortalidade em todas as concentracoes, P. hispidinervum a partir de 1,5 L/t e Melaleuca sp. nas concentracoes de 2,0 e 2,5 L/t. A reducao do numero de ovos viaveis e de insetos emergidos foi de 100% para todos os oleos essenciais, exceto Melaleuca sp. Por outro lado, os oleos fixos, apesar de apresentarem baixa mortalidade em todas as concentracoes testadas, reduziram em praticamente 100% o numero de ovos viaveis e de insetos emergidos.

Atividade acaricida dos óleos essencias de folhas e frutos de Xylopia sericea sobre o ácaro rajado (Tetranychus urticae Koch)

The essential oils of the leaves and fruits obtained by hydrodistillation of Xylopia sericea, collected in the restinga area of Pernambuco, were analyzed by GC (HP 5890 SERIES II) and GC/MS (HP 5890B SERIES II/ MSD 5971). A major part of the volatile components identified in the oils of fruits and leaves were monoterpenes and sesquiterpenes. Cubenol (57.43%) and a-epi-muurolol (26.09%) were the main compounds found in the leaves, whereas b-pinene (45.59%) and a-pinene (17.18%) were the fruits major components. The acaricidal activity of the essential oils was evaluated for Tetranychus urticae. The oil of the leaves was more active than that of the fruits showing an LC50 value of 4.08 µL/L of air for a 72 h period.

Estudo comparativo do óleo essencial de Eugenia punicifolia (HBK) DC. de diferentes localidades de Pernambuco

The essential oils obtained from the leaves of Eugenia punicifolia by hydrodistillation, which were collected from two different locations of Pernambuco (Serra Negra and Brejo da Madre de Deus), have been investigated by GC/MS. Linalol was found to be the main component of this oil from SN (44,0%) and BMD (61,2%). About 66,2% of the oil constituents from SN and 74,2% from BMD are oxygenated monoterpenes, with predominance of b-cariofileno (SN: 22,7 and BMD: 16,2%). With exception of a-cadinol, present only in the oils from plants colleted in Brejo da Madre de Deus, the chemical composition of both samples was quite similar, the only difference was the relative content among their components.

Chemical composition and acaricidal activity of the leaf and fruit essential oils of Protium heptaphyllum (Aubl.) Marchand (Burseraceae)

Essential oils from leaves and fruits of Protiumheptaphyllum collected in Tamandare beach Pernambuco/Brazil were analysed by GC/MS and tested for toxicity and repellent effect against the two spotted spider mite (Tetranychus urticae). The major constituent identified in the fruits was a-terpinene (47.6 %) whereas oil from leaf contained mainly sesquiterpenes such as 9-epi-caryophyllene (21.4 %), trans-isolongifolanone (10.7 %) and 14-hydroxi-9-epi-caryophyllene (16.7 %). The fruit oil was found to be more effective against the mite when compared to the leaf oil. Both showed mortality properties and oviposition deterrence in higher concentration (10 µl.l-1 air), but only the essential oil from fruits induced repellence on T. urticae.

Toxicidade de formulações de nim (Azadirachta indica A. Juss.) ao ácaro-rajado e a Euseius alatus De Leon e Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae)

The toxicity of selected commercial formulations of neem on Tetranychus urticae Koch (Acari: Tetranychidae) and two predatory mites Euseius alatus De Leon and Phytoseiulus macropilis (Banks) was studied. Topical toxicity was tested with the commercial formulations (Natuneem, Neemseto and Callneem) and extract of neems seeds at concentration 1%, compared to the standard acaricide abamectin at concentration of 0.3 ml/L and the control treatment (distilled water). Based on the best performance against T. urticae through topical contact, the formulation Neemseto was selected to be evaluated using different concentrations against eggs, and residual and repellent effects on adults of the mites. Egg treatment consisted of dipping eggs into Neemseto dilutions and control treatment for five seconds. In addition, residual and repellent effects of Neemseto for adult mites consisted of using leaf discs dipped into the dilutions for five seconds. The toxicity of Neemseto on eggs and adults was greater for T. urticae compared to the toxicity observed for the predatory mites. Neemseto was repellent for T. urticae and E. alatus when tested at the concentrations of 0.25, 0.50 and 1.0%, and did not affect P. macropilis. Neemseto using all concentrations, while for the predatory mites significant reduction of mite fecundity was only observed at the largest concentrations reduced the fecundity of T. urticae significantly. So Neemseto, among tested neem formulations, performed better against the twospotted spider mite and exhibited relatively low impact against the predatory mites studied.

Toxicidade por fumigação, contato e ingestão de óleos essenciais para Sitophilus zeamais Motschulsky, 1885 (Coleoptera: Curculionidae)

A especie Sitophilus zeamais e uma das principais pragas do milho armazenado no Brasil. O controle e feito, comumente, utilizando-se medidas de higienizacao e limpeza, bem como inseticidas sinteticos fumigantes e protetores. A busca por produtos menos toxicos, biodegradaveis e seguros do ponto de vista ecologico, e muito bem aceita pela sociedade. Assim, os objetivos do presente trabalho foram testar a toxicidade de contato e ingestao e fumigante de oleos essenciais e do composto orgânico natural eugenol para adultos de S. zeamais. Os valores de CL50 dos oleos essenciais provenientes de folhas de Piper hispidinervum, Eugenia uniflora, Cinnamomum zeylanicum, P. marginatum, Schinus terebinthifolius, Melaleuca leucadendron, dos frutos verdes de S terebinthifolius e do composto eugenol, nos testes de contato e ingestao, foram estimados em 1,0; 11,6; 14,2; 21,1; 57,7; 75,8; 98,8 e 14,8 µL/40 g de milho, respectivamente. As razoes de toxicidade (RT) variaram entre 1,3 e 98,8. Na fumigacao em adultos, as concentracoes letais dos oleos variaram de 0,53 a 94,7 µL/L de ar, obedecendo a seguinte ordem decrescente de toxicidade: P. hispidinervum > P. aduncum > S. terebinthifolius > frutos verdes de S. terebinthifolius > P. marginatum > eugenol e as RT variaram entre 2,0 a 178,7.

Antibacterial and cytotoxic properties of some plant crude extracts used in Northeastern folk medicine

In the present study, 32 hexane and ethanol extracts of Protium bahianum, P. heptaphyllum, Croton sellowii, C. rhamnifolius, C. jacobinensis, C. micans and Muntingia calabura were screened for antibacterial activity by the disc-diffusion method. Cytotoxicity assays using the brine shrimp Artemia salina Leach as a model were performed to determine lethal doses for 50% of individuals (LC50 µg/mL). Antibacterial activity was found in flowers hexane extracts of M. calabura against B. subtilis, and leaves ethanol extracts against S. aureus and B. subtilis at concentration of 1mg/mL. Among 32 extracts, 19 showed low or no toxicity (LC50 > 250 µg/mL), 6 showed moderate toxicity (LC50 between 80 µg/mL and 250µg/mL), and 7 were highly toxic (LC50 < 80 µg/mL).

Toxicidade de natuneem sobre Tetranychus urticae Koch (Acari: Tetranychidae) e ácaros predadores da família Phytoseiidae

A toxicidade de diferentes concentracoes de Natuneem a Tetranychus urticae Koch e a dois acaros predadores, Euseius alatus De Leon e Phytoseiulus macropilis (Banks), foi estudada. Foi avaliada a toxicidade sobre ovos, e o efeito residual e repelente, sobre adultos. O tratamento dos ovos consistiu na imersao em diluicoes de Natuneem por cinco segundos, e o efeito residual e repelente sobre adultos consistiu na imersao de discos de folhas de Canavalia ensiformes (L.) DC. tambem em diluicoes por cinco segundos. Natuneem foi repelente para T. urticae e E. alatus, quando testado nas concentracoes de 0,25; 0,50 e 1,00%, e exibiu efeito neutro para P. macropilis. A toxicidade de Natuneem a ovos e adultos foi maior para T. urticae comparada a toxicidade observada para os acaros predadores. A fecundidade de T. urticae foi reduzida significativamente por Natuneem em todas as concentracoes, enquanto para os acaros predadores a reducao foi significante apenas nas maiores concentracoes. Natuneem, nas concentracoes testadas, apresentou melhor acao sobre o acaro-rajado e menor impacto para os acaros predadores.

Biotic and abiotic stress-induced phenylpropanoids in leaves of the mango (Mangifera indica L., Anacardiaceae)

It is now widely recognized that plant’s chemical composition is affected by both abiotic and biotic stress. This is the case of Mangifera indica leaves which respond very clearly to the damages caused by the grasshopper Tropidacris collaris and to mechanical damage by biosynthesizing several stress-related volatile compounds, mainly phenylpropanoids such as myristicin, dillapiole, eugenol and eugenol acetate. The identification of these phenylpropanoids in mango leaves in response to abiotic and biotic stress factors is a key step in the search for new natural pesticides, since phenylpropanoids have various biological activities, mainly insecticidal.