Flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch (Coleoptera: Curculionidae) and its relationship with susceptibility to insecticides / Atividade de vôo de Sitophilus oryzae (L) e Sitophilus zeamais Motsch (Coleoptera: Curculionidae) e a sua relação com a susceptibilidade a inseticidas

Insect-pest mobility can influence insect susceptibility to the insecticides used to control them. The objective of this work was to evaluate the flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch populations reared on corn and wheat grains, and its relationship with insecticide susceptibility. Unsexed adult insects with ages between 10 and 20 days were placed on a plastic tray. A 40-watt incandescent light bulb was positioned at a 50 cm height relative to the tray. Flight activity was evaluated during 30 min. In the LC50 estimation bioassays, the insects were exposed to dry residues of the organophosphorus insecticide fenitrothion and of the pyrethroid insecticide esfenvalerate on the internal surface of glass vials. Mortality was evaluated 24h after installation of the experiments. Sitophilus zeamais showed greater flight activity when compared with S.oryzae; likewise, insects reared on corn had greater flight activity than those reared on wheat. Sitophilus oryzae was less susceptible to the insecticides studied than S. zeamais. Adults reared on wheat were more susceptible to the insecticides than those reared on corn. This study demonstrates that the lower flight activity of S. oryzae is related to its greater tolerance to insecticides.

A mobilidade de insetos pragas pode influenciar sua susceptibilidade aos inseticidas usados no seu controle. O objetivo do presente trabalho foi avaliar a atividade de vôo em populações de Sitophilus oryzae (L) e Sitophilus zeamais criadas em grãos de milho e trigo, e a sua relação com a susceptibilidade a inseticidas. Insetos adultos não-sexados, com idades entre 10 e 20 dias, foram colocados sobre bandeja plástica. Uma lâmpada de luz incandescente de 40 watts foi posicionada a 50 cm de altura em relação à bandeja. A atividade de vôo foi avaliada durante 30 min. Nos bioensaios para estimar a CL50 os insetos foram expostos a resíduos secos do organofosforado fenitrotiom e do piretroide esfenvalerato sobre a superfície interna de tubos de vidro. A avaliação da mortalidade foi feita 24h após a instalação dos experimentos. Sitophilus zeamais apresentou maior atividade de vôo quando comparada a S. oryzae; outrossim, os insetos criados no milho apresentaram maior atividade de vôo do que aqueles criados no trigo. Sitophilus oryzae foi menos susceptível aos inseticidas estudados do que S. zeamais. Os adultos procedentes da criação em trigo foram mais susceptíveis aos inseticidas do que aqueles procedentes da criação em milho. O presente trabalho demonstra que a menor atividade de vôo de S. oryzae está relacionada a sua maior tolerância a inseticidas.

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.

Leaf dislodgeable residues of deltamethrin applied in different types of formulations in staked cucumbers

Pesticide residues, especially in fruit and vegetsble production, raise worries about the consumers' health and the workers who need to return to the treated crops with these pesticides. The objective of this work was to study the occurence and behavior of dislodgeable residues of deltamethrin pyrethroid inseticide, applied in different types of formulations on leaves of a staked cucumber crop as a starting point for occupation exposure studies. The treatments were: (a)control; (b)three applications of 30 mL Decis 25 EC.100 L-1 water; (d) three applications of 3.75 mL Decis 200 CS.100 L-1 water. All decis treatments consisted of 0.75 g a.i deltamethrin 100L-1 water. Samples were taken (-1); zero; 1; 3; 5; 7 and 14 days after the last application. The analytical method consisted of the extraction of deltamethrin residues with Sur-ten solution, clean-up of the extracts by gel permeation chromatography (GPC), with elution made with a mixture of ethyl acetate/cyclohexane. The quantitative determination was done by gas chromatograph, using electron capture detector. The dislodgeable residues of deltamethrin were righerin CS as compared to the both EC's (4-20 times), with hal-life values of 2.8; 3.8 and 32.2 days, respectively for the formulation ma pose higher danger to workers, it is emphazide the need of the proper use of individual protection equipament when applying thse chemicals or returning to treated areas to perform other crop tasks...

Metabolism of carbosulfan to carbofuran and to 3-hydroxy-carbofuran in orange leaves

The biochemical degradation pathway of pesticides under field conditions can yield metabolites that require a more complete toxicological evaluation once they might be so or even more toxic than the parent compounds. The objective of this study was to evaluate the metabolism of the inseticide/acaricide carbosulfan to carbofuran and to 3-hydroxy-carbofuran, based on their residues in orange leaves. Two field experiments were carried out, both with the following treatments: a - control; b - one application of 10 g of carbosulfan . 100 L-1 of water; c - one application with twice the amount applied in treatment b; d - four applications with the same amount applied in treatment b. Samples were taken at (-1), zero, 1, 3, 7, 14, 21 and 28 days after the last or unique application. The quantitative determinations were done by by gas chromatography, using a nitrogen-phosphorus detector. The carbosulfan metabolism to carbofuran was fast and both had low persistence in the leaves (3 days). The same trend was observed for the carbofuran metabolism to 3-hydroxy-carbofuran, which was produced in very low amount and rapidly dissipated

Pirimiphos-methyl residues in corn and popcorn grains and in some of their processed products

Insecticides are used for stored cereal protection against insect attack and the occurrence of their residues needs to be evaluated not only in grain but also in the processed products. This study evaluates the residue degradation/persistence of the organophosphorous insecticide pirimiphos-methyl in corn and popcorn grains and in some of their processed products such as bran, hominy and corn flour from corn and popped popcorn. Grains were treated with pirimiphos-methyl at the rate of 12 mg.kg-1 (a.i.). Samples were taken and analyzed at zero, 15, 30, 60, 120 and 240 days after treatment. The analytical method consisted of residue extraction with acetone, clean-up partition with acetonitrile/hexane and silica gel column chromatography eluted with a mixture of hexane + acetone. Quantitative measurements were made by gas chromatography, using flame photometric detector (GLC/FPD). The limits of quantitation (LOQs) were: corn grain, hominy and popped popcorn 0.05 mg.kg-1; bran, corn flour and popcorn grain 0.1 mg.kg-1. Pirimiphos-methyl residues were not persistent in either types of grains or in their processed products. At the end of sampling period (240 days), 5 to 8-fold less residues were found in corn bran and popcorn. Hominy and corn flour showed low levels of contamination. Higher residue concentrations in corn bran than in grains are related to the higher oil content in that processed product

Pirimiphos-methyl residues in corn and popcorn grains and some of their processed products and the insecticide action on the control of Sitophilus zeamais Mots. (Coleoptera: Curculionidae) / Resíduos de pirimifós-metil em milho, milho pipoca, em alguns de seus produtos derivados e ação no controle de Sitophilus zeamais Mots. (Coleoptera: Curculionidae)

The degradation/persistence of residues of the organophosphorus insecticide pirimiphos-methyl was determined in corn and popcorn grains and in some of their processed products such as grain, bran, hominy and corn flour from corn and prepared popcorn and grain from popcorn. The action of the insecticide on the control of the corn weevil, Sitophilus zeamais Mots., was also evaluated. The grains were treated with the concentration of 12 mg.kg-1 (ppm) a.i. pirimiphos-methyl for the control of the weevils. Samples were taken at zero, 15, 30, 60, 120 and 240 days after treatment. Quantitative measurements were made by gas chromatography, by using a flame photometric detector. For pirimiphos-methyl residual action studies, samples of both types of grain were taken at 15, 30 days after treatment and subsequently at monthly intervals up to one year. Treated and non-treated (control) grains were infested with weevil adults. Mortality was checked 15 days after exposure. Pirimiphos-methyl residues were not persistent in either types of grains or their processed products. Residues dropped 5- 8-fold in corn bran and popcorn. They were stable in hominy and corn flour, but the concentration levels were low. Higher residues in corn bran than in grain are related to the higher oil content in that processed product. The insecticide remained effective against the pest over the entire period of observation (1 year) for both types of grains.

Foi avaliada a degradação/persistência dos resíduos do inseticida organofosforado pirimifós-metil em grãos e produtos derivados de milho (farelo, canjica e farinha de milho) e de milho pipoca (pipoca), bem como a ação residual do inseticida no controle do gorgulho do milho, Sitophilus zeamais Mots. Os grãos foram tratados com a concentração de 12 mg.kg-1 (ppm) de ingrediente ativo para controle do gorgulho. As amostras foram tomadas logo após o tratamento e também aos 15, 30, 60, 120 e 240 dias após o tratamento. A determinação quantitativa foi feita por cromatografia em fase gasosa, usando-se um detector fotométrico de chama. Para os estudos sobre a ação residual de pirimifós-metil, amostras de ambos os tipos de grãos foram tomadas aos 15 e 30 dias após o tratamento e subseqüentemente a intervalos mensais pelo período de um ano. Grãos tratados e não-tratados (testemunha) foram infestados com adultos do gorgulho. A mortalidade foi avaliada 15 dias após a exposição. Os resíduos de pirimifós-metil não foram persistentes em ambos os tipos de grãos nem nos seus produtos derivados. Os resíduos decresceram 5-8 vezes no farelo de milho e na pipoca. Na canjica e na farinha de milho eles foram estáveis, porém os níveis foram baixos. Resíduos maiores no farelo do que nos grãos estão relacionados com o maior teor de óleo no produto processado. O inseticida manteve-se eficiente contra a praga por todo período de observação (1 ano) para os dois tipos de grãos.