Avaliação dos danos de Oebalus spp. em genótipos de arroz irrigado

Abstract

Resumo -O objetivo deste trabalho foi avaliar a reação de genótipos de arroz irrigado ao dano causado por percevejos adultos (Oebalus spp., Hemiptera: Pentatomidae), confinados nas panículas, durante os períodos de desenvolvimento e maturação das espiguetas. Dez genótipos foram comparados pelas perdas quantitativas, qualitativas e totais provocadas por O. poecilus, no primeiro e segundo experimentos de campo, respectivamente. Paralelamente, cinco genótipos do primeiro experimento foram comparados quanto às perdas quantitativas causadas por O. ypsilongriseus. Ocorreu reação significativamente diferente entre os genótipos com relação às duas espécies de percevejo. O. poecilus causou uma perda geral média, nos dois experimentos, de 52,7%. A porcentagem média de perda total foi maior em Metica 1 e CNA 7545, e menor, na linhagem CNA 8033.Termos para indexação: Oryza sativa, espigueta, perda, inseto. Evaluation of damages caused by Oebalus spp. in irrigated rice genotypesAbstract -The objective of this study was to evaluate the reaction of irrigated rice genotypes to the damage caused by adult paddy bugs (Oebalus spp., Hemiptera: Pentatomidae) during spikelet development and maturation. Quantitative and qualitative losses, as well as total loss, caused by O. poecilus were compared among ten genotypes in the first and second field experiments, respectively. At the same time, five genotypes, in the first experiment, were also compared to damage caused by O. ypsilongriseus. Significant differences were observed among the evaluated genotypes in relation to reaction to insect species. For both experiments, the overall average loss caused by O. poecilus was 52.7%. The average total loss was greater for Metica 1 and CNA 7545 and smaller for CNA 8033.

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

“…Also, with the same insect density, the percentage of empty spikelets (ES) found by the authors was 31.7%, value close to 33.4% here observed. However, Ferreira et al (2002) infested the panicles over the entire grain development period, which corresponds to about 40 days, whereas in the present study, the infestation was only at the R5 stage and for seven days. In Ferreira et al (2002), the bugs had a longer feeding period, which was reflected in the greater number of spikelets (qualitative damages), but even so, the values of empty spikelets were similar (quantitative damages), demonstrating that in the cultivar IRGA 424 RI, O. poecilus significantly reduced the weight of the spikelets in a shorter time.…”

“…When the infestation was of two bugs/panicle,the percentage of stung spikelets (SS) was 56.6%, value smaller than 70.8% recorded by Ferreira et al (2002), in five irrigated rice genotypes also infested with two O. poecilus individuals. Also, with the same insect density, the percentage of empty spikelets (ES) found by the authors was 31.7%, value close to 33.4% here observed.…”

“…The impact of this insect feeding varies according to the phenological stage of the plant Krinski & Foerster, 2017). During flowering (R4) and milky-grain (R5) stages, the number of empty spikelets may be increased, their weight may be reduced by partial or complete removal of the endosperm, favoring micro-organisms contamination, causing spots on the spikelets and on the grain as well as to reduce seed germination (Ferreira et al, 2002;Krinski & Foerster, 2017). In the soft dough phase (R6), in addition to favoring fungal contamination and causing stains on the grains, they can also weaken them structurally, which facilitates the breakage during the grain processing, reducing the percentage of whole grains (Barrigossi, 2008).…”

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

“…A comparação de genótipos de arroz irrigado, considerando-se os diferentes tipos de perdas provocadas por O. poecilus, foi realizada com base na metodologia utilizada por Ferreira et al (2002b No início da fase leitosa das espiguetas, quatro dessas panículas foram infestadas, cada uma com dois adultos de O. poecilus oriundos de criação sustentada na linhagem de arroz CNA 8502, em telado. As outras duas panículas isoladas não foram infestadas e serviram de testemunha.…”

“…Apesar de as cultivares resistentes ao percevejodo-grão ainda não serem utilizadas, os trabalhos que avaliaram a suscetibilidade de genótipos a perdas quantitativas (Ferreira et al, 2002a(Ferreira et al, , 2002bFerreira & Barrigossi, 2004), qualitativas (Chaves et al, 2001) e aos dois tipos de perdas simultaneamente (Ferreira et al, 2002b;Silva et al, 2002) indicam essa possibilidade. O controle biológico depende da preservação dos inimigos naturais conhecidos.…”