Quantitative and qualitative damage caused by Oebalus poecilus (Hemiptera, Pentatomidae) to upland rice cultivated in new agricultural frontier of the Amazon rainforest (Brazil)

Abstract

Index terms: Oryza sativa; stink bug of panicles; damage level; integrated pest management. RESUMOOebalus poecilus (Dallas 1851) é uma das espécies de percevejos de grande importância econômica para os produtores de arroz no Brasil em sistemas de cultivo irrigados, de inundação ou de terras altas. Estes pentatomídeos são conhecidos como percevejos das panículas, porque ninfas e adultos alimentam-se principalmente dessas estruturas. O ataque deste percevejo resulta em grãos manchados, massa inferior, redução germinativa e grãos deformados. Considerando isso, o objetivo deste estudo foi avaliar as perdas quantitativas e qualitativas na cultivar comercial de arroz de terras altas (variedade Cambará), submetidas a diferentes níveis de infestação de percevejos de panículas, O. poecilus, em diferentes estágios de crescimento reprodutivo das plantas de arroz. Os resultados mostram que em arroz de terras altas (variedade Cambará), os grãos de arroz são suscetíveis a danos quantitativos (número e peso) e qualitativos (grãos manchados, atrofiados, gessados e quebrados), durante todo o desenvolvimento da panícula. No entanto, quando os insetos se alimentam durante os estágios de antese/cariopse e leitosa causam percentual significativamente maior de grãos vazios (até 83%) do que quando se alimentam de grãos durante as fases posteriores do desenvolvimento da panícula. Esta característica foi também observada para a redução de peso dos grãos. Esta informação pode beneficiar os produtores e outros pesquisadores, permitindo que concentrem os esforços de monitoramento de O. poecilus em fases mais suscetíveis ao ataque deste inseto. Também serve de base para a tomada de decisão sobre quando e quais medidas de controle devem ser realizadas, a fim de controlar os percevejos das panículas.Termos para indexação: Oryza sativa; percevejo das panículas; nível de dano; manejo integrado de pragas.

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

“…The number of spikelets to be produced is mainly related to the genetic characteristics of the cultivars and is not influenced by the attack of the bugs since this occurs after the panicle emission by the plant, when the number of spikelets has already been determined. Similarly, in other rice cultivars, Silva et al (2018) and Krinski & Foerster (2017) also found no influence of feeding on the number of spikelets formed.…”

“…These damages vary according to the stage when the bugs attack, and soon after the flowering stage, the number of empty spikelets increases, but as grains develop, they become less consumed by the insects, which are not able to make them completely empty, however, they reduce the content of the endosperm and its weight, as a consequence Barrigossi, 2008;Krinski & Foerster, 2017). In the present study, as insect density raised, the amount of completely empty and lighter spikelets increased, mainly as a result of competition among individuals, since only one development stage was used.…”

“…The importance of this bug relies on the fact that nymphs and adults feed by sucking the endosperm contents of the spikelets, causing direct and indirect damages to the grains (Blackman & Stout, 2017). 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).…”

“…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).…”

“…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.…”