L. R. P. Trevizan

Flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch (Coleoptera: Curculionidae) and its relationship with susceptibility to insecticides

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 24 h 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.

Acephate and methamidophos residues in greenhouse and in field grown tomatoes

O aumento da producao horticola em cultivo protegido necessita de estudos mais detalhados acerca da ocorrencia de residuos de agrotoxicos, devido as condicoes ambientais peculiares nesse sistema, no qual pragas de pouca importância no campo assumem relevância. Avaliou-se os residuos dos inseticidas acefato e de seu metabolito metamidofos em tomate sob cultivo protegido e em campo. Os tratamentos aplicados foram: (a) testemunha; (b) uma aplicacao de 75 g i.a. acefato.100 L-1 de agua; (c) uma aplicacao com 150 g i.a.100 L-1 de agua; (d) quatro aplicacoes na dosagem de 75 g i.a.100 L-1 de agua. As amostras foram tomadas a (-1), zero, 1, 3, 7, 14 e 21 dias apos a ultima ou unica aplicacao. A determinacao quantitativa foi feita por tecnica de cromatografia em fase gasosa, usando-se detector fotometrico de chama. Os residuos de acefato e de metamidofos nos frutos de cultivo protegido e de campo, sempre estiveram abaixo dos respectivos limites maximos de residuos (LMRs) em todo o periodo de colheita das amostras. Ainda, o metabolismo de acefato a metamidofos foi muito baixo nos frutos, particularmente importante nas folhas, mas nao foi bem caracterizado no solo. Os residuos de acefato foram maiores no cultivo protegido do que no campo, especialmente em folhas e no solo, sendo tambem estaveis e persistentes, em geral ate a amostragem de 7 dias apos a aplicacao.

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)

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.

Insecticidal Effect and Residual Action of Fenitrothion and Esfenvalerate on Sitophilus oryzae and S. zeamais (Coleoptera: Curculionidae) in Stored Maize and Wheat

Among the pests that attack stored maize and wheat grain, Sitophilus oryzae (L.) and S. zeamais Motsch (Coleoptera: Curculionidae) are the most destructive. This paper is aimed at the study of the insecticidal effect and the residual action of organophosphate fenitrothion, pyrethroid esfenvalerate, and the mixture of both on S. oryzae and S. zeamais in stored maize and wheat. Grains were treated in order to obtain theoretical concentrations of 10 and/or 0.5 mg·kg−1 fenitrothion and esfenvalerate, respectively. The effectiveness experiments were installed as of 15, and 30 days, and subsequently at monthly intervals as of 12 months after grain treatment, or until mortality ceased in the plots. After mortality evaluation happened all individuals were eliminated, either dead or alive, and grains were kept for 60 days to assess the number of emerged progeny. The comparison of mortality curves of the pest species within each combination of grain type and insecticide showed significant differences. In general, the mortality of S. oryzae decreased faster than that of S. zeamais considering the grain type-insecticide combination. Esfenvalerate was ineffective in all combinations. Higher mortality of both species was observed on wheat grains treated with fenitrothion and fenitrothion

Effect of spray volume on the moisture of stored corn and wheat grains

The goal of this work was to evaluate the effect of spray volume on the moisture of the stored grains of the corn and wheat. Two kg of each type of the grain were placed into the plastic bags and sprayed with the theoretical doses of 0, 1, 3, 5, 8, and 10 liters of water / ton of the grain. The grain moisture content was evaluated 24 h after the spray operation by the oven method. The increase in the grain moisture was quadratic and showed the same trend in both the corn and wheat. The grain moisture after spraying 10 L.t-1 showed little increase (0.8 %) as compared to the initial moisture content. Thus, the application of any spray volume as used in this study made no difference for a possible better uniformity in the distribution of insecticide throughout the sprayed material.

Residues of carbosulfan and its carbofuran metabolites and 3-hydroxy-carbofuran in oranges

The objectives of this study were to evaluate the residues of the insecticide carbosulfan and its carbofuran metabolites and 3-hydroxy-carbofuran in orange compartments (whole fruit, bagasse and juice) and comparison between the residual levels found in fruits with the maximum residue level and the safety interval established by the Brazilian legislation. Two field experiments were carried out, both with the following treatments: a-check; b-one application of 10 g of carbosulfan . 100 L-1 of water; c-one application with twice the rate applied in treatment b; d-four applications with the same rate 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 gas chromatography technique, using a nitrogen-phosphorus detector. The carbosulfan metabolism to its carbofuran metabolite was rapid (3 days), being both analytes concentrated in the bagasse (peel + flavedo + albedo). However, the metabolism of carbofuran to 3-hydroxy-carbofuran was of low intensity or this metabolite was quickly dissipated. Carbosulfan residues and its metabolites did not penetrate into the fruit, thus not contaminating the juice. The use of the pesticide was adequate, with respect to fruit consumption, in relation to the Brazilian legislation.

Deltamethrin residues applied in different formulations in staked cucumber and the actions of insecticides on the pickleworm control

Residuos de agrotoxicos, principalmente em hortalicas e frutas, sao motivo de preocupacao para a saude dos consumidores e operarios que necessitam retornar as areas tratadas com esses agrotoxicos. Os objetivos deste estudo foram: (a) estudar o comportamento dos residuos de deltametrina resultantes de aplicacoes de diferentes formulacoes em frutos de pepino; e (b) correlacionar os teores do inseticida nos frutos com o controle da broca-das-cucurbitaceas. Os tratamentos foram: (a) testemunha; (b) tres aplicacoes de 30 mL de deltametrina 25 CE 100 L-1 de agua (formulacao concentrado emulsionavel); (c) tres aplicacoes de 7,5 mL de deltametrina 100 CE 100 L-1 de agua (concentrado emulsionavel); e (d) tres aplicacoes de 3,75 mL de deltametrina 200 SC 100 L-1 de agua (suspensao concentrada). As amostras foram tomadas a (-1), zero, 1; 3; 5; 7 e 14 dias apos a ultima aplicacao. Os residuos foram determinados por tecnica de cromatografia gasosa, com o uso de detector de captura de eletrons. Para a avaliacao da eficiencia do inseticida foram feitos seis levantamentos de infestacao nas mesmas epocas. Os residuos de deltametrina nos frutos, embora em baixos niveis, encontravam-se acima do limite maximo de residuo (LMR = 0,03 mg kg-1, mesmo um dia apos o termino do intervalo de seguranca (2 dias), sendo maiores quando decorrentes da formulacao SC. O inseticida nas formulacoes em que foi aplicado foi eficiente no controle da praga durante todo o periodo de avaliacao.

Resíduos de tiametoxam, aldicarbe e de seus metabólitos em folhas de cafeeiro e efeito no controle de Leucoptera coffeella (Guérin-Mèneville) (Lepidoptera: Lyonetiidae)

The coffee leaf miner Leucoptera coffeella (Guerin-Meneville), one of the major pests of coffee crops in Brazil, is mainly controlled with insecticides. The objective of this study was to evaluate the residues and the translocation of the insecticide thiamethoxam in coffee leaves, as well as to study its effect on the coffee leaf miner control, comparing it with aldicarb, used as standard. One experiment was set up in the county of Garca, SP from December/2001 to August/2002. The treatments used were: aldicarb 150 G at the rates of 2.25 and 4.50 g a.i./pit, thiamethoxam 10 GR, at the rates of 0.15 and 0.30 g a.i./pit and check. Twig samples were collected prior to and 30 , 60, 90, 120, 150, 180, 210 and 240 days after the application, at three coffee plant heights (lower, middle and upper third), and the percentage of mined leaves was evaluated. The determination of aldicarb residues, including their sulphoxide and sulfone metabolites and of thiamethoxam were performed by gas chromatography with a nitrogen-phosphorus and mass spectrometer detectors, respectively. The results indicated a uniform translocation of both insecticides in all three thirds of the coffee plants when applied to the soil. A higher persistence of thiamethoxam was verified with its residues being found for as far long as eight months following the application, while aldicarb residues, including the sulphoxide and sulfone metabolites, were found only until four to six months after the application. Control of the coffee leaf miner was observed with both insecticides.

A system to evaluate the performance of hydraulic nozzles used in stored grain preotection trials

We developed a system to evaluate the performance of hydraulic nozzles used in stored corn and wheat grain protection experiments. An insecticidal mix was used as test fluid to determine the transversal volumetric distribution and droplets spectrum of a model TJ-60 8002EVS hydraulic nozzle. A mobile application system was built to apply a rate equivalent to 5 L t-1 and obtain theoretical concentrations of 10 and 0.5 mg kg-1 of fenitrothion and esfenvalerate, respectively. The corn and wheat grains were spread out as a fine layer. Three glass slides (0.1 × 0.05 m) were placed on the top surface of the grains to ensure that the intended application rate was achieved. After treatment, the deposits on both matrices were analyzed by gas chromatography. The fenitrothion deposit was higher than esfenvalerate, and the deposit on wheat was higher than on corn grains (P < 0.05). The deposits on the glass slides reached values of 100 and 93% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. Deposits on the grains were lower than on the glass slides, with values of 64 and 52% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. The results obtained demonstrate a high effectiveness of the method for evaluation of the performance of hydraulic nozzles when an insecticidal mix is used as test fluid. The factors that influenced insecticide deposition on glass slides and on grains are discussed in the present work.

Deltamethrin residues in wheat grains and their processed products evaluated by gas chromatography.

O objetivo do presente estudo foi avaliar a degradacao/persistencia do inseticida piretroide deltametrina em graos de trigo e em seus produtos processados, a saber: farelo, farinha branca, farinha integral e pao. Os graos foram tratados de modo a alcancar a concentracao teorica de 0,35 mg kg-1 do piretroide. As amostras foram tomadas a zero, 15, 30, 60 e 90 dias apos a aplicacao. Houve tendencia de concentracao do piretroide no farelo de trigo e um menor acumulo nas farinhas, sendo que apos o processo de cozimento do pao observou-se perda do inseticida.