Produção e qualidade do grão do arroz irrigado infestado por adultos de percevejo-das-panículas

Abstract

Resumo -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. Yield and grain quality of flood rice infested with adults of rice stink bugAbstract -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.

Quantitative and qualitative damages of Oebalus poecilus on irrigated rice in southern Brazil

“…There was observed a reduction of 32.7% in the weight of the two-insect infested panicle, a value greater than that recorded by Ferreira & Barrigossi (2006), 27.7%, when they evaluated 20 genotypes of irrigated rice also infested with two O. poecilus adults. The authors exposed the panicles at R5-R9 stage to the insects, whereas in this work this only occurred in the most susceptible stage of the spikelets (R5) (Krinski & Foerster, 2017), thus the damage caused by the bug feeding on IRGA 424 RI was more pronounced, indicating that this cultivar is more susceptible to the attack of these insects than the genotypes evaluated by the authors.…”

“…Abiotic factors such as temperature and relative humidity of the air and biotic factors, such as the presence of natural enemies and the susceptibility of cultivars may also affect the damage intensity (Barrigossi, 2008;SOSBAI, 2016). Several studies have demonstrated differences among genotypes of rice in relation to total spikelet loss (qualitative and quantitative) due to attack of bugs, however, they were carried out using cultivars adapted to the Central-West region or even to an upland rice system (Silva et al, 2018;Ferreira & Barrigossi, 2006;Krinski & Foerster, 2017). Rev.…”

Influence of the vegetation management of the leeves in irrigated rice organic in diversity of Hymenoptera parasitoids

“…: Noctuidae), a polyphagous insect that causes great damage to rice crops (Ferreira and Barrigossi, 2004). There were also registers of Eulophidae individuals parasitizing Odonata eggs (Fursov and Kostyukov, 1987), a group frequently found in this system, favored by areas that stay flooded for a long period throughout the year.…”

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“…This process facilitates the entry of fungi from the genus Bipolaris Shoemaker, Fusarium Link, Neovossia Körnicke, Alternaria Nees, Curvularia Boedijn, and Nigrospora Zimmerman, among others [5], causing the symptomatology known as "grain staining." Therefore, the established relation between infestations is greater than 0.7 insects/panicle of O. insularis, and the infection rate recorded in the "milky" grain phase affects the crop yield [6], [7].…”