The toxicological impact of chemical pesticides on fungal entomopathogens and their use in tank-mixing can be directly measured through in vitro compatibility tests. This study reports the in vitro ...toxicity of eight insecticides, four fungicides and five herbicides in the conidial germination, vegetative growth and conidiation of Metarhizium anisopliae (strain CG 168). A conidial suspension containing the pesticide at recommended field dosage was subjected to constant agitation in a rotary shaker for 3h to simulate a tank mixing. Then, aliquots of each suspension were used to determine conidial germination, vegetative growth and conidiation on potato dextrose agar (PDA). The fungicides difenoconazole (69 mL ha-1), propiconazole (75 mL ha-1), trifloxystrobin (313 g ha-1) and azoxystrobin (56 mL ha-1) were the most harmful products to all biological stages of M. anisopliae and they should not be applied together with this fungus in tank mixing. The insecticides exhibited the least degree of toxicity to this fungal pathogen, whereas the herbicides had the greatest impact on mycelial growth. The agrochemicals compatible with M. anisopliae were the insecticides methyl parathion (240 mL ha-1), thiamethoxam (31 g ha-1), and lambda-cyhalothrin (6.3 mL ha-1) and the herbicides glyphosate (1560 mL ha-1), bentazon (720 mL ha-1), and imazapic+ imazapyr (84 g ha-1). The compatible pesticides could be simultaneously used with this bio-control agent for integrated pest management in rice production systems.
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
Tibraca limbativentris (percevejo-do-colmo) é um inseto altamente prejudicial à cultura do arroz no Brasil. O objetivo com este trabalho foi definir a distribuição espacial de T. limbativentris e aperfeiçoar o método de amostragem por meio da aplicação de técnicas geoestatísticas e construção de mapas de predição em arrozal irrigado por inundação, no Planalto da Campanha do Rio Grande do Sul. Os experimentos foram realizados em lavoura de arroz situada no município de Itaqui - RS, nos anos agrícolas de 2009/10, 2010/11 e 2011/12, efetuando-se amostragens quinzenais para contagem de ninfas e adultos, conforme grids georreferenciados com pontos espaçados em 50m na primeira safra e em 10m nas demais safras. Realizou-se a análise geoestatística via ajuste de semivariogramas e da interpolação dos dados numéricos por krigagem ordinária para verificar a dependência espacial e posterior mapeamento populacional. Os resultados obtidos indicaram que o percevejo do colmo, T. limbativentris, possui forte dependência espacial. Os mapas de predição permitem estimar a densidade populacional da praga e a visualização de sua distribuição espacial em lavoura de arroz irrigado por inundação, possibilitando o aperfeiçoamento do método de amostragem tradicional para o percevejo-do-colmo
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Rice, Oryza sativa L. (Poaceae), is one of the world's most important food crops. Among the insects that damage rice grains, the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is ...the most important species. The objective of this study was to identify rice varieties with resistance to S. oryzae as measured by grain feeding damage and S. oryzae reproduction. The rice varieties evaluated were obtained from the germplasm bank of the National Center of Research Rice and Beans, Embrapa, Brazil. The experimental design was completely randomized with 3 replications and 22 treatments (varieties). The varieties Bonança, Esmeralda, and Rio Verde had the antibiosis and/or antixenosis type of resistance, providing high rates of mortality, low rates of adult emergence, and low rates of grain consumption by S. oryzae. The varieties Pepita and Progresso were susceptible, with a high rate of S. oryzae adult emergence and grain consumption. The presence or absence of a fissure in the grain was a major morphological characteristic determining susceptibility or resistance to S. oryzae in rice varieties.
This study aimed to observe the response of 34 rice accessions to attack by sugarcane borer (Diatraea saccharalis Fabr., 1794) and to analyze the genetic diversity of these accessions by ...microsatellite markers. Twenty larvae were placed on the leaf sheaths of rice plants. At 30 days after infestation the rice plants at ground level were taken to the laboratory where the signs of borer attack, external and internal diameter of the stem and weight of surviving larvae were determined. For the molecular analysis of rice accessions, 24 microsatellite markers were used. The results of the morphological traits of the rice plant, response of the plant to insect attack, development of the sugarcane borer larvae and molecular data, indicated a genotypic variation. The accessions that most favored larval survival were IAC 47 and Ti Ho Hung. Larvae with highest weight (0.0986 g and 0.0862 g) and the largest internal diameters of the rice stem (3.18 mm) were found in land races “Canela de Ferro” (rust colored stem) and all these “Canela de Ferro” accessions also remained genetically grouped. The most tolerant materials, based on the ability to produce new tillers after larval infestation were, Chiang an Tsao Pai Ku and IR 40 which remained morphological and genetically grouped. The results of this study indicate that all the traits and molecular analyses were able to separate the accessions of rice into different groups in relation to resistance to the sugarcane borer. These materials can be used as donor sources in breeding for genetic resistance to sugarcane borers and can be used as donors to amplify the genetic base of Brazilian rice.
•We correlate morphological traits with molecular data of rice accessions.•We identify rice genotypes resistant to Diatraea saccharalis.•We analyze the genetic diversity of rice accessions by microsatellite markers.•Rice genotypes with similar resistance to the sugarcane borer were grouped.•Donor sources for breeding rice for resistance to borer are identified.
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 aimed to observe the response of 32 rice accessions to attack of sugarcane borer (Diatraea saccharalis). Twenty larvae were placed on the leaf sheaths of rice plants. At 30 days after ...infestation, the rice plants were cut at ground level and taken to the laboratory to analyse the signs of borer attack, external and internal diameter of the stem and weight of surviving larvae. The results of the morphological traits of the rice plant, response of the plant to insect attack and development of the sugarcane borer larvae indicated a genotypic variation. The accessions that most favored larval survivals were IRAT 124 and MEARIN. Larvae with highest weight (0.0643 g) were found in IAPAR L 99-98 and the largest internal diameters of the rice stem (5.65 mm) were found in LAC 12. The results of this study indicate that, all the morphological traits were able to separate the accessions of rice into different groups in relation to resistance to the sugarcane borer D. saccharalis.
The babassou plant (Attalea speciosa Mart. Ex. Spreng, Arecaceae) is an important palm tree in the state of Maranhão, northeastern Brazil. This plant is the main arboreal component in extensive ...geographical areas including agricultural areas. However, limited research studies exist on its role as an alternative pest host in this region. This study investigated the occurrence of Tibraca limbativentris Stal (1860) in young babassou palm trees, the effect of abiotic factors (temperature, solar radiation and rainfall) on the number of T. limbativentris adults and postures, and this insect’s spatial arrangement during the rice crop off-season. The research team inspected young babassou plants on a monthly basis in 2012 and 2013 to collect and quantify postures and adults. They collected a total of 1418 live adults, 13 dead and ten postures of T. limbativentris. There was a significant difference between the first and the other collections of live adults carried out in 2012 and 2013. Abiotic factors including rainfall, temperature and solar radiation, had no influence on the number of adults (alive and dead) and postures. The semivariogram adjusted to the Gaussian model showed that in 2013, the spatial distribution of living adults, that had an aggregate pattern, was highly dependent on the season. However, in 2012 there was a pure nugget effect. These results imply that young babassou plants are alternative T. limbativentris hosts.
ABSTRACT The rice stem bug, Tibraca limbativentris Stal (Hem.: Pentatomidae), is one of the main insect pests in Brazilian rice crops. Knowledge of its spatiotemporal distribution can support the ...development of an effective sampling system and improve IPM strategies. This study aimed to map the spatiotemporal distribution of rice stem bug in flooded rice crop in Southern Brazil. Flooded rice crop was scouted for two seasons to estimate insect densities. Four occurrence categories were observed: no insect, only adults, only nymphs, and both phases. The relationship between phenological stages and insect categories was established. Interpolation (mapping) of occurrence categories of T. limbativentris was performed by multiquadric equations. In two seasons during the rice cycle, the results indicate that rice stem bug “adults" were the most abundant category until the mid-vegetative phase of the rice; “nymphs" were the most abundant from the end of vegetative phase; “adults + nymphs" occurred from the beginning of reproductive phase; there were no rice stem bugs in more than 66% of the area, as they were most concentrated near the edge of the crop. The information presented here provides further knowledge about T. limbativentris spatiotemporal dynamics that can be applied to improve IPM strategies, such as developing sampling plans and localized control measures at the edge of rice fields.
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