Luidi Eric Guimarães Antunes

Efeito da dose e exposição à terra de diatomácea de diferentes insetos em milho armazenado

Sitophilus zeamais and Tribolium castaneum are important insect pests of stored grain and their damage corresponds to approximately 25% of post-harvest losses in Brazil. The methods used for the control of these pests notably include the use of post-harvest inert dusts. Therefore, the objective was to assess the mortality of adult S. zeamais and T. castaneum with the use of diatomaceous earth (DE) at different dosages and durations. The treatments with diatomaceous earth were 1,000 and 2,000 GT-1 and control (no application). Insects (10 each species) were placed in 300-ml plastic containers containing 100 g of corn kernels with different moisture contents (12, 14 and 16% wb). Infestations occurred 1 hour, 10 and 20 days after the application of TD. Mortality was evaluated at 30 and 60 days. There were five replicates per treatment. There was a higher mortality for the species S. zeamais than for T. castaneum, and this morality rate increased in direct relation to insect exposure time. It was concluded that T. castaneum has greater tolerance and that the more time the insects are in contact with treated grain the greater the mortality.

Eficiência de inseticidas durante o armazenamento de grãos de milho

O objetivo foi verificar a mortalidade de adultos de Sitophilus zeamais infestando graos de milho tratados com diferentes inseticidas ao longo de 240 dias de armazenamento. Foram utilizados dois inseticidas, um piretroide liquido da marca Starion® 25 CE (Bifentrina) e outro organofosforado liquido da marca Actellic® (Pirimifos metilico), sendo as doses de 6 e 8 mL do produto, diluido em 2 litros de agua, com aplicacao de 2 mL da solucao por quilo de graos. Para o tratamento controle usou-se 2mL de agua. Cada dosagem foi aplicada em tres lotes de 1 kg, com uso de pulverizador uni-spray, com tres repeticoes para cada tratamento, sendo avaliados em duplicata de 50 g, em delineamento inteiramente casualizado. A cada periodo de 30 dias apos as aplicacoes, ocorreram as infestacoes com 20 adultos de S. zemais , sendo a mortalidade verificada apos 15 dias de contato. As infestacoes ocorreram 30, 60, 90, 120, 150,180, 210 e 240 dias apos a aplicacao dos produtos. Ate 60 dias apos a aplicacao, ambas as dosagens de Pirimifos metilico causaram mortalidade acima de 80%, porem apos esse periodo apenas a dosagem de 8 mL ficou acima de 88%. Ja a dosagem de 8mL de Bifentrina, aos 30 dias, apresentou 51,04% de mortalidade, sendo a maior nos tratamentos com este inseticida. Resistencia e degradacao dos inseticidas sao possiveis causas da baixa mortalidade. Conclui-se que Pirimifos metilico com dosagem de 8mL representa a melhor forma de controle de S. zeamais .

EFICIÊNCIA DO USO DE TERRA DE DIATOMÁCEA NA PROTEÇÃO DE GRÃOS DE MILHO - DOI: 10.13083/1414-3984.v22n06a02

Among the main methods of insect control on post-harvest grain, highlighted is the use of diatomaceous earth. Thus, it was proposed to test the efficiency of different dosages of this inert powder on control of Sitophilus zeamais adults in maize grains during storage. Five repetitions were performed with 100 g of grains with different moisture contents (12, 14, and 17%), infested with 20 insects, and treated with different dosages (0, 500, 1500 and 2500 g. t-1) in h hours and 15 days after application of the product. Mortality of insects in the grains, loss of weight, humidity and technological analysis of grains was performed at 60 days after each period of infestation. There were no statistical differences between the averages of mortality regardless of the treatment and moisture content. The control treatments of all moistures presented greater weight losses in both periods of infestation. Higher moisture content was found in untreated grains with initial value of 17%. Higher values of rotten grains were obtained for untreated grains, independent of the moisture content and infestation period. It was therefore concluded that the treatment with diatomaceous earth is effective for the control of S. zeamais and reduces damage to corn grains.

Custos da secagem estacionária de milho submetido a diferentes fontes de aquecimento do ar

The purpose of this study was to evaluate the consumption and cost of fuel and electricity for stationary drying of grains subjected to three heating sources. Grains originated from experimental crops were dried to approximately 12% moisture content with natural air, the use of LPG (liquefied petroleum gas), and solar drying. Assessments of time consumption and costs, unitary and total, were carried out for the LPG drying. Evaluations of electricity total consumption and cost per dry bag were also performed, as well as the total drying cost for all treatments studied. The cost of drying per bag (60 kg) with the use of LPG was three times higher than with natural air and ten times higher than with solar drying. The total electricity consumption was greater with natural air and the drying rate with the use of LPG was three times higher when compared to natural air-drying. Recebido: 22/06/2011 Aceito: 20/03/2012