Seasonal abundance and mortality of Oebalus poecilus (Dallas) (Hemiptera: Pentatomidae) in a hibernation refuge

Oebalus poecilus (Dallas) is an important pest affecting irrigated rice in Rio Grande do Sul, Brazil. It hibernates during the coldest months of the year in refuges such as bamboo litter. This study examined O. poecilus hibernation to determine the causes of mortality during this period. The study was conducted in a 140 m² bamboo plantation located in a rice-growing area in Eldorado do Sul County (30° 02’ S and 51° 23’ W), RS. During June 2000 to April 2002, 63 samples of litter were taken in weekly or fortnightly intervals, and the number of bugs recorded in the laboratory. The arrival at the hibernation site (bamboo litter) began in the first fortnight of March, and was completed in the beginning of May. O. poecilus left this refuge from middle October to the end of December. Parasitism by tachinid flies and Beauveria bassiana (Bals.) Vuill. fungus were the most important mortality factors

Spatial distribution of Oebalus poecilus (Dallas, 1851) (Hemiptera: Pentatomidae) in hibernation

Oebalus poecilus é considerada uma das mais importantes pragas na orizicultura brasileira. Neste trabalho estudou-se a distribuição espacial deste inseto durante sua hibernação em folhedo de bambu. Para o número de insetos/unidade de amostra foi testado o ajuste das freqüências observadas às esperadas, de acordo com as distribuições Poisson, binomial negativa e positiva, também foram obtidos os índices de dispersão I e de Morisita, o parâmetro k da distribuição binomial negativa e b da lei de potência de Taylor. A variância amostral foi superior a média em 92,3% das ocasiões de amostragem, com índice I e de Morisita superiores estatisticamente a unidade. O coeficiente b de Taylor mostrou-se superior estatisticamente a unidade. Das ocasiões em que se testou o ajuste das freqüências obtidas à distribuição binomial negativa, constatou-se que em apenas quatro ocasiões não houve ajuste para esta série. Esses resultados evidenciam que a praga se distribui de forma agregada no sítio de hibernação

Distribui\ue7\ue3o espacial de Oebalus poecilus (Dallas, 1851) (Hemiptera: Pentatomidae) durante a hiberna\ue7\ue3o

SANTOS RSS, REDAELLI LR, DIEFENBACH LMG, ROMANOWSKI HP, PRANDO HF, ANTOCHEVIS RC. 2004. Spatial distribution of Oebalus poecilus (Dallas, 1851) (Hemiptera: Pentatomidae) in hibernation. Entomotropica 19(2):91-100. Oebalus poecilus is considered one of the most important pests in rice culture in Brazil. In this paper, the spatial distribution of this insect during its hibernation in bamboo foliage litter was studied. For the number of insects/sample unit, the adjustment of observed frequencies to the expected ones was tested, according to the Poisson, negative and positive binomial distributions; the Morisita and dispersion I indexes, the k parameter of negative binomial distribution and b of the Taylor power law were also obtained. The sample variance was higher than the average in 92.3% of the sampling occasions, with Morisita and I index statistically higher than the unit. From the occasions when the adjustment of obtained frequencies to the negative binomial distribution was tested, we could verify that only in four occasions there was no adjustment for this series. These results evidence that the pest is distributed in an aggregated mode at the hibernation site.SANTOS RSS, REDAELLI LR, DIEFENBACH LMG, ROMANOWSKI HP, PRANDO HF, ANTOCHEVIS RC. 2004. Distribui\ue7\ue3o especial de Oebalus poecilus (Dallas, 1851) (Hemiptera: Pentatomidae) durante a hiberna\ue7\ue3o. Entomotropica 19(2):91-100. Oebalus poecilus \ue9 considerada uma das mais importantes pragas na orizicultura brasileira. Neste trabalho estudou-se a distribui\ue7\ue3o espacial deste inseto durante sua hiberna\ue7\ue3o em folhedo de bambu. Para o n\ufamero de insetos/unidade de amostra foi testado o ajuste das freq\ufc\ueancias observadas \ue0s esperadas, de acordo com as distribui\ue7\uf5es Poisson, binomial negativa e positiva, tamb\ue9m foram obtidos os \uedndices de dispers\ue3o I e de Morisita, o par\ue2metro k da distribui\ue7\ue3o binomial negativa e b da lei de pot\ueancia de Taylor. A vari\ue2ncia amostral foi superior a m\ue9dia em 92,3% das ocasi\uf5es de amostragem, com \uedndice I e de Morisita superiores estatisticamente a unidade. O coeficiente b de Taylor mostrou-se superior estatisticamente a unidade. Das ocasi\uf5es em que se testou o ajuste das freq\ufc\ueancias obtidas \ue0 distribui\ue7\ue3o binomial negativa, constatouse que em apenas quatro ocasi\uf5es n\ue3o houve ajuste para esta s\ue9rie. Esses resultados evidenciam que a praga se distribui de forma agregada no s\uedtio de hiberna\ue7\ue3o

Distribuição espacial de Oebalus poecilus (Dallas, 1851) (Hemiptera: Pentatomidae) durante a hibernação

SANTOS RSS, REDAELLI LR, DIEFENBACH LMG, ROMANOWSKI HP, PRANDO HF, ANTOCHEVIS RC. 2004. Spatial distribution of Oebalus poecilus   (Dallas, 1851) (Hemiptera: Pentatomidae) in hibernation. Entomotropica 19(2):91-100. Oebalus poecilus is considered one of the most important pests in rice culture in Brazil. In this paper, the spatial distribution of this insect during its hibernation in bamboo foliage litter was studied. For the number of insects/sample unit, the adjustment of observed frequencies to the expected ones was tested, according to the Poisson, negative and positive binomial distributions; the Morisita and dispersion I indexes, the k parameter of negative binomial distribution and b of the Taylor power law were also obtained. The sample variance was higher than the average in 92.3% of the sampling occasions, with Morisita and I index statistically higher than the unit. From the occasions when the adjustment of obtained frequencies to the negative binomial distribution was tested, we could verify that only in four occasions there was no adjustment for this series. These results evidence that the pest is distributed in an aggregated mode at the hibernation site