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

Resumo

Oebalus poecilus is one of the most important pests of irrigated rice in Brazil. However, the impact of this species on the cultivar IRGA 424 RI, which is the most used, is unknown. Hence, the objective of this work is to evaluate the damage caused by O. poecilus on cv IRGA 424 RI. Panicles of this cultivar were infested for seven days at the R5 stage, using a randomized block design, considering the following factors sex, insect reproductive stage and insect density (number/panicle). In order to analyze the effect of these factors, the qualitative and quantitative damage caused by stink bugs to panicles were evaluated. An interaction was found between the sex and developmental stage for quantitative variables, in which reproductive females were responsible for increasing the damage in comparison to pre-reproductive females and the males, while the greatest qualitative damage was caused by reproductive insects regardless of sex and by females, despite the reproductive stage. Density of only one infesting insect has already increased the qualitative damage, while significant losses on the weight of the grain were verified with the infestation of two insects, demonstrating that IRGA 424 RI is susceptible to the attack of these stink bugs.