Flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch (Coleoptera: Curculionidae) and its relationship with susceptibility to insecticides

Abstract

-Insect-pest mobility can infl uence insect susceptibility to the insecticides used to control them. The objective of this work was to evaluate the fl ight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch populations reared on corn and wheat grains, and its relationship with insecticide susceptibility. Unsexed adult insects with ages between 10 and 20 days were placed on a plastic tray. A 40-watt incandescent light bulb was positioned at a 50 cm height relative to the tray. Flight activity was evaluated during 30 min. In the LC 50 estimation bioassays, the insects were exposed to dry residues of the organophosphorus insecticide fenitrothion and of the pyrethroid insecticide esfenvalerate on the internal surface of glass vials. Mortality was evaluated 24h after installation of the experiments. Sitophilus zeamais showed greater fl ight activity when compared with S. oryzae; likewise, insects reared on corn had greater fl ight activity than those reared on wheat. Sitophilus oryzae was less susceptible to the insecticides studied than S. zeamais. Adults reared on wheat were more susceptible to the insecticides than those reared on corn. This study demonstrates that the lower fl ight activity of S. oryzae is related to its greater tolerance to insecticides.

Costs of dispersal

“…These correlations are likely to be expressed between and within dispersal‐related phenotypic traits including morphological, physiological, behavioural and life‐history traits. Genetic trade‐offs between functional wings and insecticide resistance (Vasquez‐Castro et al , 2009) or disease resistance (Adamo & Parsons, 2006; Calleri et al , 2006) are examples of deferred survival costs. Investments in flight morphology for long‐distance movements reduces acceleration speed in butterflies, inducing a negative impact on male‐male interactions and subsequent territory‐holding ability (Berwaerts, Aerts & Van Dyck, 2006; Bonte & Van Dyck, 2009; Kemp, Wiklund & van Dyck, 2006).…”

Flutuação populacional e distribuição de Sitophilus zeamais em pomares de pessegueiro e macieira

“…A ocorrência desta espécie já havia sido relatada em frutas de caroço, como pêssego, ameixa, nectarina, maçã e uva (Salles, 2003;Botton et al, 2005aBotton et al, , 2005bHickel & Schuck, 2005), e está relacionada a falhas no armazenamento do milho (Salles, 2003;Botton et al, 2005b), que é o cereal mais cultivado em pequenas propriedades rurais nas regiões produtoras de pêssego. A maior atividade de voo de S. zeamais em comparação a S. oryzae (Vásquez-Castro et al, 2009) também pode ser determinante para a migração e a ocorrência da espécie em pomares de pessegueiro e macieira.…”

Insecticidal Effect and Residual Action of Fenitrothion and Esfenvalerate onSitophilus oryzaeandS. zeamais(Coleoptera: Curculionidae) in Stored Maize and Wheat

“…The greater susceptibility to fenitrothion when both species were reared on wheat grains would be another hypothesis to explain for these results. Vásquez-Castro et al [35], using the dry film method observed higher susceptibility of both species to fenitrothion when reared on wheat grains, compared to maize. On the other hand, due to the operational characteristics of the treatment, in which the grains were uniformly spread in a thin layer and treated 6 ISRN Agronomy by using a double-jet hydraulic nozzle (60 degree-betweenjets angle), and as to the morphological characteristics of grains, wheat presented a higher specific surface of contact to the drops.…”

“…In Brazil, resistance to organophosphate insecticides was detected in several populations of S. oryzae [7]; but just slightly resistance to one insecticide of this group (chlorpyriphos methyl) was detected in S. zeamais [8,34]. The higher susceptibility of S. zeamais compared to S. oryzae occurs because the first species presents greater flight activity, among other factors, favoring cross-infestation and gene flow, thus preserving the genes of susceptibility to insecticides [35].…”