Studies on the behavior of Helicoverpa armigera in relation to soybean cultivars expressing Bt proteins are fundamentally important for IPM. We determine the no-choice and feeding choice of H. armigera, the no-choice and oviposition choice in different Bt and non-Bt soybeans cultivars. In the first step it was carried out the experiment to determine the no-choice and food choice in test for 12 Bt and non-Bt soybean cultivars. Simultaneously the consumption was determined. In a second step it was evaluated the no-choice and oviposition choice in different soybean cultivars. Helicoverpa armigera caterpillars showed neither attractiveness and preference for food nor attractiveness and oviposition preference for Bt and non-Bt soybean leaves when simultaneously contrasting the tested cultivars. This study showed that Bt toxin did not influence the oviposition preference, and H. armigera adults did not differentiate Bt and non-Bt soybean cultivars for oviposition indicating no behavioral preference. Third instar caterpillars showed no discrimination between Bt and non-Bt soybean leaves. Research in this area must focus on the possibility of widespread planting of genetically modified soybeans containing the Bt protein, which is associated with selection pressure and the behavior of pest species in relation to their hosts, as well as on the adequacy of management tactics that is able to prevent the loss of technology efficiency.
Exposure of Helicoverpa armigera to sublethal concentrations of insecticides can cause physiological deficiencies manifested by reduced longevity, development, fertility and fecundity. Research on the sub-lethal effects, to identify the non-lethal negative impacts of insecticides on pests can provide practical information for integrated management. The objective of this study was to determine the lethal concentrations and sublethal effects of insecticides on larval development and reproduction of H. armigera. The insecticides were diluted in water and applied via immersion of soybean leaf discs directly in the solution for three second, subsequently provided to the larvae maintained under controlled conditions for a period of 48 h. For surviving larvae, artificial diet was provided with daily evaluation until pupation. The pupae obtained were weighed after 24 h and transferred to Petri dishes, covered with filter paper until the adult phase, to evaluate longevity and pupal viability. For the assessments related to oviposition, couples were separated in polyvinyl chloride (PVC) cages and fed with 10% honey solution; the counting of eggs was done every two days, until the end of the oviposition period. All of the insecticides tested presented lethal and sublethal effects on the parameters weight, mortality and pupal viability and reduced oviposition and can be used in pest management, representing an alternative in the product rotation for the control of the third instar of H. armigera.
The selection pressure generated by the incorrect use of Bt maize might result in Spodoptera frugiperda individuals resistant to the toxins synthesized by the plant. In this study was evaluated the nutritional parameters of Spodoptera frugiperda submitted to the maize that synthesize the toxins Cry1F, Cry1A105-Cry2Ab2 and Vip3Aa20, during five subsequent generations of selection pressure. The caterpillars were submitted to the treatments: Non-Bt maize (CONV), Cry1F (Bt1), Cry1A105/Cry2Ab (Bt2) and Vip3Aa20 (VIP1, VIP2 and VIP3) and exposed for a period of four days in each cycle, for five successive generations. The larval survival of S. frugiperda was evaluated in five generations. The consumed leaf area was quantified in the second generation and the nutritional indexes in the latter ones. The results indicate that caterpillars of S. frugiperda from VIPs lineage presented the lowest percentage of survival, with a high Metabolic Cost and a considerable efficiency reduction in the conversion of the digested and ingested food. The lineage maintained in VIP2 showed the lowest leaf consumption (83.13%). However, the action of Vip3Aa20 toxin on S. frugiperda resulted in a higher Metabolic Cost in reduction of leaf area consumption. However, from the third generation on there is a survival of insects exposed to Bt toxins, suggesting the surviving potential of this species in Bt maize subjected to continuous exposure to this technology. Sobrevivência e índices nutricionais de Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) mantida em milho Bt por cinco gerações RESUMO: A pressão de seleção gerada pelo uso incorreto do milho Bt pode resultar em indivíduos de Spodoptera frugiperda resistentes às toxinas expressadas pela planta. Neste trabalho foi determinado os parâmetros nutricionais de Spodoptera frugiperda submetida aos milhos que sintetizam as toxinas Cry1F, Cry1A105-Cry2Ab2 e Vip3Aa20, durante cinco gerações. As lagartas foram submetidas aos tratamentos: Milho não-Bt (CONV), Cry1F (Bt1), Cry1A105/Cry2Ab (Bt2) e Vip3Aa20 (VIP1, VIP2 e VIP3) e expostas por um período de quatro dias em cada ciclo, por cinco gerações sucessivas. Foi avaliada a sobrevivência larval de S. frugiperda em cinco gerações. A área foliar consumida foi quantificada na segunda geração e nas posteriores foram determinados os índices nutricionais. As lagartas de S. frugiperda, da geração mantida no milho VIPs, apresentaram menor porcentagem de sobrevivência, com um alto Custo Metabólico e considerável redução na Eficiência na conversão do alimento digerido e Eficiência na conversão do alimento ingerido. A geração mantida no Hibrido VIP2 apresentou o menor consumo foliar (83,13%). Contudo a ação da toxina Vip3Aa20 sobre S. frugiperda resultou no maior Custo Metabólico em redução no consumo de área foliar. Contudo a partir da terceira geração observa-se uma sobrevivência de insetos expostos as toxinas Bt, sugerindo o potencial desta espécie em sobreviver aos milhos Bt quando submetidas a exposição contínua a esta tecnologia. Palavra...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.