The control of the most important pest of stored maize, the weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), is mainly achieved with the use of pyrethroid insecticides. However, the intensive use of these compounds has led to the selection of resistant populations and has compromised the control efficacy of this insect pest. Here, the toxicity of indoxacarb for a potential use in the control of S. zeamais was assessed on 13 Brazilian populations. Concentration-mortality bioassays, in the presence of synergists (piperonyl butoxide, triphenyl phosphate, and diethyl maleate), were used to assess potential metabolic-based indoxacarb resistance mechanisms. We also assessed the behavioral (locomotory) responses of these populations to indoxacarb exposure. The results showed significant differences between the populations (LD50 values ranged from 0.06 to 13.99 mg a.i/kg of grains), resulting in resistance ratios of >200-fold between the least (Canarana-MT) and the most (Espirito Santo do Pinhal-SP) susceptible populations. The results obtained with synergized indoxacarb suggest the involvement of esterases and glutathione-S-transferases on indoxacarb action, and also suggest the involvement of cytochrome P450-dependent monooxygenases as a potential indoxacarb resistance mechanism in Brazilian populations of S. zeamais. Although indoxacarb-induced behavioral avoidance varied among populations, some resistant populations (e.g., Canarana-MT) were able to reduce exposure to indoxacarb by spending more time in the nontreated areas. Collectively, our findings indicate that the behavioral (locomotory) and physiological responses of these insects may compromise the control efficacy of oxadiazine insecticides (e.g., indoxacarb) in Brazilian populations of S. zeamais.
An understudied aspect of insecticides is their stress on non-targeted pest species. Sublethal insecticidal stress may elicit a range of protective and non-protective responses that may affect behaviour and sexual fitness of the exposed insects, which may lead to negative, neutral or stimulatory (i.e. hormetic) responses. We assessed the behavioural response of the Neotropical brown stink bug, Euschistus heros, a soybean pest in the Neotropical region with increasing pest status, following exposure to chlorantraniliprole, pyriproxyfen and spinosad, insecticides commonly used against soybean caterpillars and whiteflies. Both individuals, or only the male or female of each mating pair, were exposed. Reproductive behaviour and output were measured to determine insecticide-and gender-mediated fitness. We found that treatment scenario significantly affected mating behaviour, and that the duration of some behaviours were significantly affected. Chlorantraniliprole and pyriproxyfen reduced latency to mate, while spinosad increased this behaviour. Insecticide exposure also decreased the interacting time of each couple and male antennation of the female. Fertility table analyses of exposed couples indicated negligible effect of pyriproxyfen exposure, while spinosad extended generation time and reduced net reproductive rate, leading to lower rates of population growth of the brown stink bug. In contrast, chlorantraniliprole led to only a slight extension on the generation time, but enhanced net reproductive rate of the stink bug leading to higher rates of population growth; no effects on sexual fitness were observed, as both compounds exhibited similar effect on females and males. Latency to mate correlated significantly with the population growth rate. The positive response to chlorantraniliprole exposure reinforces the notion that sublethal exposure of the brown stink bug to this insecticide may lead to stimulatory (hormetic) response favouring its outbreaks in soybean fields.
O estudo dos insetos é fundamental para a formação de estudantes, no entanto, rotineiramente esse conhecimento é repassado superficialmente no ambiente escolar. Esta pesquisa teve por objetivo analisar a percepção de estudantes da 3ª série do Ensino Médio sobre os insetos em Cáceres, Mato Grosso, Brasil. O estudo foi realizado com 20 estudantes concluintes do Ensino Médio da Escola Estadual Cívico-Militar Senador Mario Motta. Foi aplicado um questionário semiestruturado com cinco perguntas. Todos os estudantes disseram que conhecem um inseto e, responderam corretamente a opção que apresentava somente exemplos desses artrópodes. No entanto, metade dos entrevistados (50%) não conhece com exatidão a quantidade de pernas desses animais. 55,56% dos estudantes disseram que não gostam de insetos, ao contrário de 44,44%. Quanto à importância dos insetos: 45% dos entrevistados disseram que possuem importância positiva e 55% disseram que eles possuem importância negativa e positiva. Nenhum dos estudantes relatou que os insetos possuem importância negativa, apesar de mais da metade ter dito que não gostam dos insetos. É fundamental a disseminação de conhecimentos entomológicos no meio escolar a fim de esclarecer aos estudantes que os insetos desempenham importante papel ecológico na natureza, e que não são exclusivamente animais causadores de danos ou prejuízos à saúde.
The goal of this research was to analyze the effect of flower strips and the proximity of corn fields on the environmental services of regulation by insects (pollination and biological control) in tomato crops (Solanum lycopersicum). The study was conducted using commercial tomatoes (6.200 m²) in the Brazilian Cerrado. The experimental outline was completely randomized with 15 plots of 5 x 4 meters, constructed with 16 tomato plants, in two treatments: 1) tomato plants without attractive flower strips (control) and 2) tomato plants with attractive flower strips of cilantro and sorghum. The sampling of pollinator insects and natural enemies was performed using trap-type bee bowls and active collection. Data were analyzed by generalized linear models (GLM) to compare insect diversity and abundance between treatments. As a result, the richness (p = 0.040) and abundance (p = 0.030) of pollinating insects were significantly higher in tomatoes with sorghum flowers than in the control. The effect of mixing strips of intercropped flowers (cilantro and sorghum) increased the abundance (p = 0.007) and richness (p = 0.005) of the total natural enemies and pollinators in richness (p = 0.030) and abundance (p = 0.020) in the tomato plants with the flower strips compared to the tomato plants without the strips. Our results clearly show that the use of attractive flower strips of the mix of cilantro and sorghum in interleaved periods with tomato plants contributes to the permanence of the services provided by insects to the crop field.
Caranguejos são abundantes no Pantanal e apresentam papel fundamental na cadeia trófica, pois fazem parte da dieta de mamíferos, aves, répteis e anfíbios dos ecossistemas pantaneiros. São encontrados, aproximadamente, 0.63 indivíduos/m² desses organismos no Pantanal, distribuídos em 6 espécies, entre elas, Dilocarcinus pagei (Stimpson, 1861) e Trichodactylus petropolitanus (Göldi, 1886). Esta pesquisa investigou a riqueza, abundância, morfologia e hábitos alimentares de caranguejos no Pantanal de Cáceres, sob influência urbana e área remota. As amostragens foram realizadas na Estação Ecológica de Taiamã (168 km de Cáceres) e no Rio Paraguai incorporado à paisagem da cidade de Cáceres - MT. As coletas foram feitas em bancos de macrófitas aquáticas usando tela de nylon de 2 m de comprimento x 1 m de largura. Ao todo, foram coletados 256 caranguejos sendo 226 pertencentes a espécie D. pagei e 20 da espécie T. petropolitanus. As duas espécies foram encontradas associadas às macrófitas Eichhornia crassipes e Eichhornia azurea, que formam bancos densos de plantas funcionando como locais de refúgio para os caranguejos em termos de abrigo, alimento e segurança contra predadores. Os organismos amostrados tiveram preferência, em sua base alimentar, por matéria orgânica, talo e raiz de macrófita. Adicionalmente, microplásticos e outros materiais particulados não identificados foram constatados no conteúdo alimentar, indicando prejuízo na dieta e na morfofisiologia dos caranguejos. Os nossos achados contribuem para elucidar a dieta de caranguejos no Pantanal e projetar os efeitos de poluentes, como os microplásticos, sobre esses organismos e na cadeia trófica aquática, podendo atingir a saúde humana.
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