Joelma Lima Vidal Estrela

Toxicidade de óleos essenciais de Piper aduncum e Piper hispidinervum em Sitophilus zeamais

Oleos essenciais de Piper aduncum L. e Piper hispidinervum C.DC. (Piperaceae) foram avaliados quanto ao efeito inseticida em Sitophilus zeamais Motsch. por acao de contato, fumigacao e topica. Na determinacao da DL50 e CL50, foi utilizada a analise de Probit. Medias porcentuais de mortalidade dos insetos foram comparadas por meio da analise de regressao linear e superposicao das barras do erro padrao. S. zeamais foi mais suscetivel ao efeito de contato do oleo de P. hispidinervum em relacao ao de P. aduncum, obtendo-se CL50 de 0,51 e 2,87 mL cm- 2 de oleo, respectivamente. Mortalidade proxima a 100% foi obtida nas concentracoes de 20 e 30% do oleo de P. hispidinervum. Quanto ao efeito fumigante, a susceptibilidade foi maior no oleo de P. aduncum do que no de P. hispidinervum. Houve diferenca significativa entre os oleos somente nas concentracoes de 0,1 e 1,0. A DL50 foi semelhante nos dois oleos essenciais por aplicacao topica. No entanto, a mortalidade foi maior com P. aduncum. Oleos essenciais de P. aduncum e P. hispidinervum possuem efeito inseticida em S. zeamais, mas as respostas dependem da concentracao e do metodo de exposicao a que o inseto seja submetido.

Propriedade inseticida dos óleos essenciais de Piper hispidinervum C. DC.; Piper aduncum L. e Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum sobre Tenebrio molitor L., 1758

Oleos essenciais das piperaceas Piper aduncum L., Piper hispidinervum C. DC. e da bignoniacea Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum foram avaliados para o controle de larvas de Tenebrio molitor L., 1758. Para a avaliacao do efeito por contato em superficie contaminada, foram utilizados papeis-filtro impregnados com diferentes quantidades dos oleos essenciais. Para a avaliacao do efeito topico foram aplicados 5 mL de solucoes com diferentes concentracoes dos oleos sobre larvas de quinto instar do inseto. A taxa de mortalidade foi a variavel utilizada para avaliar os experimentos. Todos os oleos essenciais apresentaram efeito inseticida sobre larvas de T. molitor, sendo que as respostas variaram em funcao da concentracao utilizada, assim como do metodo de exposicao do inseto. A toxicidade dos oleos essenciais foi elevada apresentando os seguintes valores de CL50: 0,045; 0,033 e 1,515 mL de oleo cm-2 para exposicao por contato (papel filtro) aos oleos de P. hispidinervum,P. aduncum e T. nocturnum, respectivamente. Para a aplicacao topica, os valores da DL50 foram de: 0,000025; 0,009 e 0,000015 mL de oleo mg de inseto -1 para os oleos essenciais de P. hispidinervum,P. aduncum e T. nocturnum, respectivamente. Resultados promissores para o emprego desses oleos essenciais como inseticidas foram obtidos utilizando-se concentracoes acima de 3,0% (v v-1) para P. hispidinervum e 2,5% (v v-1) para P. aduncum e T. nocturnum.

Toxicidade de amidas análogas à piperina a larvas de Ascia monuste orseis Godart (Lepidoptera: Pieridae) e Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

The objective of this study was to evaluate the toxicity piperine amide analogs to 3rd-instar larvae of Ascia monuste orseis Godart and Spodoptera frugiperda (J.E. Smith). The bioassays were based on the topical application of 0.5 µl of the following amides: N-isopenthyl-(3,4-metilenodioxiphenyl)-amide, N-isopropyl-(3,4-metilenodioxiphenyl)-amide, N-hexyl-3-(3,4-etilenodioxiphenyl)-amide and piperonyl butoxide. The DL50 (mg a.i./ mg larva) values of the amides N-isopropyl e N-hexyl to A. monuste orseis were 0,278 and 0,004, respectively, and to S. frugiperda were 1.359 and 0.613, respectively. The steeper slopes of the dose-response curves for both species were obtained with N-isopropyl, indicating the higher homogeneity of response of the pest species studied to this compound. N-isopropyl was also the most promising piperine synthetic analog as insecticide agent among the compounds studied because it was the most toxic amide to both insect-pest species.

Ação inseticida do extrato de Derris amazonica Killip para Cerotoma arcuatus Olivier (Coleoptera: Chrysomelidae

The abundance and insecticidal potential of Derris amazonica in addition to need of controlling Cerotoma arcuatus for bean crop stimulated this research. The objective of this work was to evaluate insecticide action of the extract of D. amazonica to adults of C. arcuatus in laboratory conditions. The bioassays were carried out using three distend methodologies: leaf intake, contact in treated surface (filter paper) and topical application. A completed randomized experimental design was used with four replications. Mortality values and leaf consumption of the insects were subjected to regression analyses, being the Probit analyses used to determine of the i.e., LC 50 , LT 50 and LD 50 . The extract of D. amazonica containing 3.7% of rotenone was toxic to adults C. arcuatus when exposed to treated leaves (LC 50 = 15.14 µl.mL -1 ), treated surface (LC 50 = 0.45 µl.cm -2 ) and subjected to topical exposure (LD 50 = 1.44 µl.g -1 ). In all bioassays the adults mortality was higher than 80% with lower median lethal times obtained with 5% (v.v -1 ) concentrations of the extract. Leaf consumption by adults C. arcuatus was inversely proportional to the concentration of the extract when exposed by leaf intake or topical application, also being observed inhibition of feeding individuals. The extract of D. amazonica is toxic to C. arcuatus and inhibits the feeding of insects from the concentration of 1% (v v -1 ).

Atividade inseticida do óleo essencial de Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum (Bignoneaceae) sobre Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

Insecticidal activities of Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum (Bignoneaceae) essential oil against Sitophilus zeamais Motsch. (Coleoptera: Curculionidae). The essential oil extracted from fresh leaves of the Tanaecium nocturnum (Barb. Rodr.) Bur.& K. Shum by steam distillation, was tested against maize weevil Sitophilus zeamais Motsch.. Filter paper and maize grains impregnation was employed, for contact and fumigant toxicity effect studies, respectively. For topical effect studies, aliquots of 0,5 µl of the diluted oil applied to adults insects. We used a broad range of concentrations to be used for establish the most promising concentrations. Probit analysis was employed in analyzing the dose/ concentration-mortality response (LD50 and LC50). Linear regression analysis was applied in mortality of maize weevil adults. The toxicity (LC50) T. nocturnum oil to S. zeamais was of 14.1 ng.cm-2 and LC50 of 1,321.6 ng.g-1 of the grains for contact and fumigant effects, respectively, and LD50 of 14.7 µg.mg-1 of the insect for topical application. For contact and fumigant effects, the mortality rate was nearly 100 % at oil concentrations of 2 % and 5 % (m/v), and 4 % and 5 % (m/v), respectively. For contact, fumigant, and topical effects, the mortality rate was nearly 100 % at oil concentrations of 2 % and 5 % (m/v); 4 % and 5 % (m/v) and 10 % (m/v) respectively. The current study shows that cyanidric acid, liberated from the essential oil of the T. nocturnum, posses fumigant insecticidal effect on S. zeamais in concentrations more than 4 % (m/v) were promises.

Fumigação de milho para o controle do gorgulho utilizando caule de Tanaecium nocturnum (Bignoniaceae)

The objective of this work was to assess the effect of fumigating corn grains with injured stem parts of Tanaecium nocturnum in the control of Sitophilus zeamais. The experimental design was completely randomized with seven replicates in split plots. The plots consisted of fumigation treatments and the subplots, of consecutive time intervals taken every 23 days for the evaluations. The treatments were: fumigation using 50 g of green stem parts of T. nocturnum per kilogram of corn grains; which contained between 800 and 900 mg kg-1 HCN fumigation using 60 mg of aluminum phosphide tablets per kilogram of corn grains with 57% of active ingredient; and control (no fumigation). S. zeamais infestation and weight loss of corn grains were evaluated nine times along 207 days. The use of 50 g kg-1 of stem parts of T. nocturnum for S. zeamais control produced reduction of the pest infestation and of the weight loss of grains comparable to that of aluminum phosphide. This alternative control can be adapted to maize storage conditions on small properties in Occidental Amazon.

Determinação do nível de dano econômico de Cerotoma tingomarianus Bechyné (Coleoptera: Chrysomelidae) em Phaseolus vulgaris L. cv. Pérola

The common bean cultivar Perola is widely planted in Brazil, and it is heavily attacked by leaf-feeding chrysomelids of the genus Cerotoma. The objective of this study was to determine the Economic Injury Level (EIL) for C. tingomarianus, as a basis for the establishment of an Integrated Pest Management (IPM) program for this pest in Rio Branco (Acre, Brazil). The trial was conducted at the Experimental Station of Embrapa Acre using the cultivar Perola. The experiment was arranged as a split-plot in a randomized block design, with four replications. The main plots consisted of five plants at the developmental stages: V3 = first trifoliolate leaf, V4 = third trifoliolate leaf, R6 = initiation of flowering, R7 = pod formation and R8 = pod maturation, and the sub-plots were the four defoliation levels (0%, 33%, 66% and 100%). The response variables were: 1) grain production (g/plant); 2) average duration of each plant development phase (days) and leaf area production (cm2). The formula for determination of the EIL, corrected for the number of insects sampled, was applied based on the coefficients used for the regression curves of percent defoliation versus yield reduction. New regression curves were determined as a function of these EIL and of the cost of application of the control (C2) and the cost of 1 kg of beans (C1). The high r2 values obtained for the regression curves indicate reliability in their use to determine the EIL of C. tingomarianus for the common bean cultivar Perola.