-The goal of this work was to determine by means of consumption and utilization of natural food, the existence of strains of Spodoptera frugiperda (J.E. Smith) in different areas of corn and irrigated rice in Rio Grande do Sul. Four populations were collected: one in Santa Rosa, traditional area of corn cropping; one in Uruguaiana, traditional area of rice; and two in Pelotas, where corn and rice are planted side by side. In the laboratory, 20 larvae were individualized (second generation) and kept in petri dishes, in BOD, at 25ºC temperature, 70 ± 10% RH and 14h photophase. The larvae were fed on leaves of their respective hosts, hybrid of corn BRS 8330 and the cultivar of irrigated rice Embrapa 6-Chuí. The leaves of both hosts were submitted to bromatological analysis. The dry weight of the larva at maximum development, food consumed and feces eliminated were determined and the nutritional ratios were calculated: relative consumption ratio (RCR), relative metabolic ratio (RMR), relative growth ratio (RGR), approximate digestibilidade (AD), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD) and the metabolic cost (100 -ECD). Rice was more suitable as food for S. frugiperda; it was ingested in smaller amount, presented smaller 100 -ECD and larger ECI and ECD. A strong possibility of existence of two strains of S. frugiperda is evidenced in the State of Rio Grande do Sul, the corn and rice strains, which are morphologically similar but physiologically different.KEY WORDS: Nutritional index, fall armyworm, insect strain RESUMO -O objetivo do trabalho foi verificar, através de medidas de consumo e utilização de alimento natural, a existência de raças de Spodoptera frugiperda (J.E. Smith) nas culturas do milho e do arroz irrigado no Rio Grande do Sul. Foram coletadas quatro populações: uma em Santa Rosa, região tradicionalmente produtora de milho; uma em Uruguaiana, região tradicionalmente produtora de arroz; e duas em Pelotas, região que produz milho e arroz lado a lado (uma em milho e outra em arroz). Individualizaram-se 20 lagartas de cada população (segunda geração) em placas de Petri, mantidas em BOD à temperatura de 25ºC, UR 70 ± 10% e fotofase de 14h. As lagartas foram alimentadas com folhas de seus respectivos hospedeiros, o híbrido de milho BRS 8330 e a cultivar de arroz irrigado Embrapa 6-Chuí. As folhas de ambos hospedeiros foram submetidas a análise bromatológica. Foram determinados o peso seco da lagarta no máximo desenvolvimento, do alimento consumido, e das fezes eliminadas, e calculados os índices nutricionais: taxa de consumo relativo (RCR), taxa metabólica relativa (RMR), taxa de crescimento relativo (RGR), digestibilidade aproximada (AD), eficiência de conversão do alimento ingerido (ECI), eficiência de conversão do alimento digerido (ECD) e custo metabólico (100 -ECD). O arroz apresentou-se mais adequado para a alimentação dos insetos, pois foi ingerido em menor quantidade, apresentando menor 100 -ECD, e maior ECI e ECD. Evidencia-se forte po...
Oceurrence ofA spergillus parasiticus Speaee ao adults of Spodoptera frugiperda (Abbot & Smith, 1797) (Lepidoptera, Noctuidae), in laboratory.In months of Spodoptera frugiperda (Abbot & Srnith, 1797) which suffered precoeius mortality in lhe laboratory, lhe cause of death was detcrmincd as a fungal infection caused hy ,lspergillus parasiticus. Thc growth of lhe fungus on lhe host as well as on artificial media is described. The systematic position of thc fungus, natural and artificial intections, and symptoms of infection are reported.A. parasiticus provokcd death only lo lhe aduli stage of S. frugiperda. Oral infection in larvae was lhe only way discorvercd for infection by lhe disease.
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