In order to spatial arrangement validation of Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) in flooded rice field located at the “Planalto da Campanha” Region, Rio Grande do Sul (RS), ...Brazil, was carried out a study in flooded rice fields at Itaqui, Rio Grande do Sul State, Brazil, in the 2009/10, 2010/11 and 2011/12 harvests. Were established georeferenced grids for the samplings, totaling 81 points spaced ~50 m in the 2009/10 harvest and, 693 and 352 points in the 2010/11 and 2011/12 harvests, respectively, both with equidistant points ~10 m. Adults and nymphs samplings were performed on each point of the regular grids. We conducted a descriptive statistical analysis for the adults, nymphs and adults + nymphs variables by calculations the mean, standard deviation and minimum and maximum values and dispersion indices: variance/mean, Morisita index, k index, Green coefficient and Taylor potency. The rice stem bug spatial arrangement has been validated when the dispersion indices showed similar results. The rice stem bug T. limbativentris spatial arrangement in flooded rice is the aggregate type, regardless of the infestation level and life stage of the insect.
In order to spatial arrangement validation of Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) in flooded rice field located at the “Planalto da Campanha” Region, Rio Grande do Sul (RS), ...Brazil, was carried out a study in flooded rice fields at Itaqui, Rio Grande do Sul State, Brazil, in the 2009/10, 2010/11 and 2011/12 harvests. Were established georeferenced grids for the samplings, totaling 81 points spaced ~50 m in the 2009/10 harvest and, 693 and 352 points in the 2010/11 and 2011/12 harvests, respectively, both with equidistant points ~10 m. Adults and nymphs samplings were performed on each point of the regular grids. We conducted a descriptive statistical analysis for the adults, nymphs and adults + nymphs variables by calculations the mean, standard deviation and minimum and maximum values and dispersion indices: variance/mean, Morisita index, k index, Green coefficient and Taylor potency. The rice stem bug spatial arrangement has been validated when the dispersion indices showed similar results. The rice stem bug T. limbativentris spatial arrangement in flooded rice is the aggregate type, regardless of the infestation level and life stage of the insect.
The resistance of rice stalk stink bug, Tibraca limbativentris Stal 1860 (Hemiptera: Pentatomidae) to five insecticides was investigated in the present study. The tested insecticides were ...bifenthrin, carbosulfan, etophenprox, λ-cyhalothrin, and thiametoxam. The five field-collected populations of rice stalk stink bugs from Luis Alves-GO, Flores de Goiás-GO, Formoso do Araguaia-TO, Lagoa da Confusão-TO and Itajaí-SC were investigated in relation the insecticide resistance occurrence. A further Santo Antônio de Goiás population, from natural environment was used as standard-population of susceptibility. Insects of these populations were submitted to discriminating concentrations (LC95s) with objective to determine the frequences of individuals resistants. The insects population from Formoso do Araguaia were the most resistant to all tested insecticides. The mortality values observed in this population were 76%, 86%, 72%, 80%, and 80% for carbosulfan, bifenthrin, etofenprox, λ-cyhalothrin, and thiamethoxam, respectively. The frequencies of resistant individuals ranged from 9% a 23% and were classified as moderate. The more expressive values of the resistance rate (RR) were found to the insecticide thiamethoxan 17-fold in the population of Formoso do Araguaia and 12-fold to the Luís Alves population. This first findings about insecticide resistance in T. limbativentris shows the seriousness of the problem in the region and suggests the possible occurrence of cross-selection in this species, confering insecticide resistance to one or more products of different groups. These results are usefuls as information to integrated pest management (IPM) in the regions producers of flooded rice in Brazil, as technical guidance to rice farmers and open news perspectives of investigation in this research area.
Tibraca limbativentris (rice stem bug) is an insect highly injurious to the rice crop in Brazil The aim of this research was to define the spatial distribution of the T. limbativentris and improve ...the sampling process by means of geostatistical application techniques and construction of prediction maps in a flooded rice field located in the "Planalto da Campanha" Region, Rio Grande do Sul (RS), Brazil The experiments were conducted in rice crop in the municipality of Itaqui--RS, in the crop years of 2009/10, 2010/11 and 2011/12, counting fortnightly the number of nymphs and adults in a georeferenced grid with points spaced at 50m in the first year and in 10m in the another years. It was performed a geostatistical analysis by means adjusting semivariogram and interpolation of numeric data by kriging to verify the spatial dependence and the subsequent mapping population. The results obtained indicated that the rice stem bug, T. limbativentris, has a strong spatial dependence. The prediction maps allow estimating population density of the pest and visualization of the spatial distribution in flooded rice fields, enabling the improvement of the traditional method of sampling for rice stem bug.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Tibraca limbativentris (rice stem bug) is an insect highly injurious to the rice crop in Brazil The aim of this research was to define the spatial distribution of the T. limbativentris and improve ...the sampling process by means of geostatistical application techniques and construction of prediction maps in a flooded rice field located in the "Planalto da Campanha" Region, Rio Grande do Sul (RS), Brazil The experiments were conducted in rice crop in the municipality of Itaqui--RS, in the crop years of 2009/10, 2010/11 and 2011/12, counting fortnightly the number of nymphs and adults in a georeferenced grid with points spaced at 50m in the first year and in 10m in the another years. It was performed a geostatistical analysis by means adjusting semivariogram and interpolation of numeric data by kriging to verify the spatial dependence and the subsequent mapping population. The results obtained indicated that the rice stem bug, T. limbativentris, has a strong spatial dependence. The prediction maps allow estimating population density of the pest and visualization of the spatial distribution in flooded rice fields, enabling the improvement of the traditional method of sampling for rice stem bug. Key words: Oryza sativa, rice stem bug, dispersion, monitoring. Tibraca limbativentris (percevejo-do-colmo) e um inseto altamente prejudicial a cultura do arroz no Brasil. O objetivo com este trabalho foi definir a distribuicao espacial de T. limbativentris e aperfeicoar o metodo de amostragem por meio da aplicacao de tecnicas geoestatisticas e construcao de mapas de predicao em arrozal irrigado por inundacao, no Planalto da Campanha do Rio Grande do Sul. Os experimentos foram realizados em lavoura de arroz situada no municipio de Itaqui--RS, nos anos agricolas de 2009/10, 2010/U e 20U/12, efetuando-se amostragens quinzenais para contagem de ninfas e adultos, conforme grids georreferenciados com pontos espacados em 50m na primeira safra e em 10m nas demais safras. Realizouse a analise geoestatistica via ajuste de semivariogramas e da interpolacao dos dados numericos por krigagem ordinaria para verificar a dependencia espacial e posterior mapeamento populacional. Os resultados obtidos indicaram que o percevejo do colmo, T. limbativentris, possui forte dependencia espacial. Os mapas de predicao permitem estimar a densidade populacional da praga e a visualizacao de sua distribuicao espacial em lavoura de arroz irrigado por inundacao, possibilitando o aperfeicoamento do metodo de amostragem tradicional para o percevejo-do-colmo. Palavras-chave: Oryza sativa, percevejo-do-colmo, dispersao, monitoramento.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
O objetivo deste trabalho foi comparar os danos qualitativos e quantitativos, causados por adultos de Oebalus poecilus (Dallas) Stal, em panículas de 39 genótipos de arroz irrigado. Em campo, as ...panículas emergentes foram isoladas em gaiolas e infestadas com dois insetos, no início da fase leitosa das espiguetas. Panículas não infestadas serviram de testemunha. Após a colheita, amostras compostas de 50 espiguetas de cada grau de infestação, para cada genótipo, foram semeadas em telado, e a emergência foi determinada após 16 dias. Manchas no grão foram avaliadas em amostras de 50 espiguetas. O percevejo provocou alterações significativas, pois reduziu a massa e o número de espiguetas por panícula, a porcentagem de plântulas emergidas, e aumentou a porcentagem de espiguetas vazias e com grão manchado. A combinação da porcentagem de perda de massa com a de sementes inviáveis foi de 44%, e da perda de massa com a de espiguetas manchadas, de 81,4%. A maior porcentagem de plântulas emergidas de espiguetas manchadas ocorreu nos genótipos de ciclo médio. Os genótipos de ciclo curto CNAi 8859, CNAi 8879, CNAi 8885 e CNAi 8886, e os de ciclo médio CNAi 9089, CNAi 9097, CNAi 9150, CNAi 9687 CNAi 9730, CNAi 9747 e CNAi 9778 são os mais tolerantes ao percevejo-das-panículas.
The objective of this work was to compare the effects of infestation with adults of rice stink bug, Oebalus poecilus (Dallas) Stal, on panicles of 39 genotypes of irrigated rice. In the field, newly emerged panicles were isolated in cages and infested with two insects in the beginning of the milky stage. Non-infested panicles comprised the controls. After harvest, samples of 50 spikelets from each infestation level were seeded in screen house, and the emergence was determined 16 days after planting. Stains in the grain were evaluated in samples of 50 spikelets. The stink bug produced significant alterations, reducing weight and number of spikelets per panicle, and percentage of seedlings, and increasing the percentage of empty spikelets and spikelets with stained grain. Combined percentage of weight loss with no viable seeds was 44%, and combined percentage of weight loss with stained spikelets was 81.4%. The highest percentage of seedlings emerged from stained spikelets was observed in genotypes of median season. The short season genotypes CNAi 8859, CNAi 8879, CNAi 8885 and CNAi 8886, and the median season genotypes CNAi 9089, CNAi 9097, CNAi 9150 CNAi 9687, CNAi 9730, CNAi 9747 and CNAi 9778 are the most tolerant to rice stink bug.
O objetivo deste trabalho foi comparar os danos qualitativos e quantitativos, causados por adultos de Oebalus poecilus (Dallas) Stal, em panículas de 39 genótipos de arroz irrigado. Em campo, as ...panículas emergentes foram isoladas em gaiolas e infestadas com dois insetos, no início da fase leitosa das espiguetas. Panículas não infestadas serviram de testemunha. Após a colheita, amostras compostas de 50 espiguetas de cada grau de infestação, para cada genótipo, foram semeadas em telado, e a emergência foi determinada após 16 dias. Manchas no grão foram avaliadas em amostras de 50 espiguetas. O percevejo provocou alterações significativas, pois reduziu a massa e o número de espiguetas por panícula, a porcentagem de plântulas emergidas, e aumentou a porcentagem de espiguetas vazias e com grão manchado. A combinação da porcentagem de perda de massa com a de sementes inviáveis foi de 44%, e da perda de massa com a de espiguetas manchadas, de 81,4%. A maior porcentagem de plântulas emergidas de espiguetas manchadas ocorreu nos genótipos de ciclo médio. Os genótipos de ciclo curto CNAi 8859, CNAi 8879, CNAi 8885 e CNAi 8886, e os de ciclo médio CNAi 9089, CNAi 9097, CNAi 9150, CNAi 9687 CNAi 9730, CNAi 9747 e CNAi 9778 são os mais tolerantes ao percevejo-das-panículas.The objective of this work was to compare the effects of infestation with adults of rice stink bug, Oebalus poecilus (Dallas) Stal, on panicles of 39 genotypes of irrigated rice. In the field, newly emerged panicles were isolated in cages and infested with two insects in the beginning of the milky stage. Non-infested panicles comprised the controls. After harvest, samples of 50 spikelets from each infestation level were seeded in screen house, and the emergence was determined 16 days after planting. Stains in the grain were evaluated in samples of 50 spikelets. The stink bug produced significant alterations, reducing weight and number of spikelets per panicle, and percentage of seedlings, and increasing the percentage of empty spikelets and spikelets with stained grain. Combined percentage of weight loss with no viable seeds was 44%, and combined percentage of weight loss with stained spikelets was 81.4%. The highest percentage of seedlings emerged from stained spikelets was observed in genotypes of median season. The short season genotypes CNAi 8859, CNAi 8879, CNAi 8885 and CNAi 8886, and the median season genotypes CNAi 9089, CNAi 9097, CNAi 9150 CNAi 9687, CNAi 9730, CNAi 9747 and CNAi 9778 are the most tolerant to rice stink bug.
This study was conducted to assess the economic feasibility of small scale organic production of rice, common bean and maize in Goias State, Brazil. During 2004/05 and 2005/06 growing seasons, rice, ...common bean and maize were produced at the organic farm of Embrapa Rice and Beans in five mulching systems (fallow, Crotalaria juncea, Cajanus cajan, Mucuna aterrima and Sorghum bicolor ), with and without tillage. Soil tillage consisted of heavy disc harrowing followed by light disc harrowing. All operations and used inputs were recorded. Based on those records, the production costs for each crop were estimated for each cropping season. The costs included operations like sowing, ploughing, harrowing, spraying, fertilizer broadcasting and harvesting, as well as inputs like seeds, inoculant strains of Rhizobium, neem oil and organic fertilizers. The benefits include the gross revenue obtained by multiplying the production amount with the market price for non-organic products. For the purpose of analysis of competitiveness of organic production in comparison to conventional farming the market prices assumed were those of conventional production. In the analysis, the costs of certification were not considered yet due to lack of certifiers in the region. For comparison between traits, net revenue, the benefit-cost-ratio (BCR) and the break even point were used. In 2004/05 growing season the BCR varied from 0.27 for common bean on S. bicolor mulch system with tillage up to 4.05 for green harvested maize produced after C. juncea in no tillage system. Common bean and rice were not economically viable in this growing season. In 2005/06 growing season the BCR varied between 0.75 for common bean after S. bicolor in tillage system and 4.50 for green harvested maize produced after fallow in no tillage system. In this season common bean was economically viable in leguminous mulching systems and green harvested maize was viable in all mulching systems.
Estudou-se o efeito da infestação natural de Diatraea saccharalis na produção de espiguetas de 24 genótipos de arroz de terras altas, em um experimento de campo. O efeito de colmos infestados pelas ...lagartas D. saccharalis na massa de espiguetas de amostras e da área útil das parcelas foi estimado por um índice de perda e por análise de regressão. O índice utilizado quantifica a perda de massa de espiguetas por colmo brocado em relação à massa de espiguetas de colmo não brocado. As estimativas obtidas pelos dois métodos foram discrepantes. Menos de 10% dos genótipos manifestaram relação linear ou quadrática entre a infestação e o dano da broca-do-colmo. Perdas calculadas por esse índice mostraram-se mais adequadas às condições do experimento. A infestação de D. saccharalis aparentemente não afetou a massa de espiguetas em cinco dos genótipos, causou pequenas reduções em dois genótipos e, na maioria deles (17 genótipos), causou reduções de importância econômica. O genótipo CNAs9023 teve a menor infestação e a maior massa de espiguetas, demonstrando maior resistência em comparação à linhagem CNAs9028, que foi o genótipo mais infestado e com menor produção.
PALAVRAS-CHAVE: Arroz de terras altas; broca do colmo; amostragem; avaliação de genótipos.
The impact of the Diatraea saccharalis natural infestation on yield of 24 genotypes of upland rice was studied in an experiment carried out in field conditions. The attack of D. saccharalis on stems and its effect on spikelet weight was determined using a yield loss index and by regression analysis. The index used quantifies the spikelet mass loss per bored stem in relation to spikelet mass no bored stem. The estimates obtained with these two methods were different. Less than 10% of genotypes showed a linear relationship between the infestation and stem borer damage. Estimated yield losses based on the index seemed more appropriate to the conditions of the experiment. Infestations by D. saccharalis did not visibly affect the weight of spikelets of five genotypes, caused a small reduction in two genotypes, and caused economic losses in the most of them (17 genotypes). The CNAs9023 genotype was the least infested and presented the highest weight of spikelets, and showed more resistance than CNAs9028, which was more infested and produced less.
KEY-WORDS: Upland rice; stem borer; sampling; genotype evaluation.
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