Resistência de milho convencional e transgênico e efeitos da idade da planta no desenvolvimento de Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)
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2018-07-10
Autores
Faria, Stéfane Carolina Quista da Silva
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Universidade Estadual Paulista (Unesp)
Resumo
Dentre as principais pragas da cultura do milho (Zea mays L.), a lagarta-do-cartucho, Spodoptera frugiperda (Lepidoptera: Noctuidae), é considerada a mais prejudicial. Por ser uma praga polífaga e ocorrer em todas as regiões produtoras, tanto na primeira safra, como nos de segunda safra (safrinha), causa consideráveis perdas na produção. Com a frequente utilização do milho transgênico, populações de insetos resistentes às proteínas Bt são a maior ameaça a essa tecnologia. Portanto, o presente estudo tem por objetivo avaliar em condições de campo a infestação de S. frugiperda em híbridos de milho convencional e transgênicos com diferentes eventos Bt e os danos causados pelo ataque da lagarta; e, em laboratório, avaliar o efeito do milho Bt e não Bt no desenvolvimento de lagartas de S. frugiperda. Nos experimentos conduzidos em condições de campo foram avaliados os danos causados pela lagarta nos diferentes estádios do milho. Foi constatado que os híbridos Bt com as tecnologias Herculex® (Cry1F) e Optimum Intrasect® (Cry1F + Cry1Ab) tiveram danos semelhantes ao híbrido não Bt avaliado. O híbrido com tecnologia Viptera® (VIP3Aa20) apresentou menores notas de dano causado por S. frugiperda. Em condições de laboratório, foi avaliada a influência dos diferentes híbridos de milho no desenvolvimento de lagartas de primeiro e terceiro ínstar. As seguintes variáveis foram analisadas: tempo de sobrevivência em lagartas de primeiro ínstar; duração das fases larval e pupal, peso de lagartas aos 14 dias de idade, sobrevivência larval aos 14 dias e da fase larval, viabilidade pupal, peso de pupas com 24 horas de idade, porcentagem de pupas e adultos deformados, razão sexual, longevidade dos adultos e duração do ciclo para as lagartas de terceiro ínstar. As principais variáveis biológicas de S. frugiperda, como período larval, peso de pupas e longevidade de adultos foram afetadas em função do tamanho da lagarta exposta ao híbrido transgênico, pela idade da planta e pela proteína inseticida expressa pela planta de milho Bt. As lagartas de primeiro ínstar são mais suscetíveis que as lagartas de terceiro aos efeitos das toxinas Bt, independente da tecnologia. Lagartas de terceiro ínstar alimentadas com híbridos de milho com as tecnologias PowerCoreTM, Herculex® e Optimum Intrasect® têm desenvolvimento similar às lagartas alimentadas com milho não Bt.
Among the main pests of the maize crop (Zea mays L.), the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), can be considered the most damaging. Because it is a polyphagous pest and occurs in all producing regions, both in the first crop and in the off-season, its causes considerable losses in prodution. With the frequent use of transgenic maize, insect populations resistant to Bt proteins are the greatest threat to this technology. Therefore, the present study aims to evaluate in field conditions the infestation of S. frugiperda in conventional and transgenic maize hybrids with different Bt events and the damages caused by the caterpillar attack; and in the laboratory, to evaluate the effect of Bt and non-Bt maize on the development of S. frugiperda caterpillars. In the experiments conducted under field conditions, the damage caused by the caterpillar in the different corn stages was evaluated. It was found that the Bt hybrids with Herculex® (Cry1F) and Optimum Intrasect® (Cry1F + Cry1Ab) technologies had similar damages to the non-Bt hybrid evaluated. The hybrid with Viptera® technology (VIP3Aa20) was the most efficient in the control of S. frugiperda. In the second phase, under laboratory conditions, the influence of the different maize hybrids on the development of first and third instar caterpillars was evaluated. The following variables were analyzed: survival time in first instar caterpillars; larval and pupal stages, pupal viability, pupal weight at 24 hours, percentage of deformed pupae and adults, sex ratio, longevity of pupae and larval stages, larval stage survival at 14 days and pupal viability. The main biological variables of S. frugiperda, such as larval period, pupal weight and adult longevity were affected by the size of the caterpillar exposed to the transgenic hybrid, by the age of the plant and by the insecticidal protein expressed by the Bt maize plant. First instar caterpillars are more susceptible than third caterpillars to the effects of Bt toxins, regardless of technology. Third instar larvae fed corn hybrids with PowerCoreTM, Herculex® and Optimum Intrasect® technologies have similar development to caterpillars fed on non-Bt maize.
Among the main pests of the maize crop (Zea mays L.), the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), can be considered the most damaging. Because it is a polyphagous pest and occurs in all producing regions, both in the first crop and in the off-season, its causes considerable losses in prodution. With the frequent use of transgenic maize, insect populations resistant to Bt proteins are the greatest threat to this technology. Therefore, the present study aims to evaluate in field conditions the infestation of S. frugiperda in conventional and transgenic maize hybrids with different Bt events and the damages caused by the caterpillar attack; and in the laboratory, to evaluate the effect of Bt and non-Bt maize on the development of S. frugiperda caterpillars. In the experiments conducted under field conditions, the damage caused by the caterpillar in the different corn stages was evaluated. It was found that the Bt hybrids with Herculex® (Cry1F) and Optimum Intrasect® (Cry1F + Cry1Ab) technologies had similar damages to the non-Bt hybrid evaluated. The hybrid with Viptera® technology (VIP3Aa20) was the most efficient in the control of S. frugiperda. In the second phase, under laboratory conditions, the influence of the different maize hybrids on the development of first and third instar caterpillars was evaluated. The following variables were analyzed: survival time in first instar caterpillars; larval and pupal stages, pupal viability, pupal weight at 24 hours, percentage of deformed pupae and adults, sex ratio, longevity of pupae and larval stages, larval stage survival at 14 days and pupal viability. The main biological variables of S. frugiperda, such as larval period, pupal weight and adult longevity were affected by the size of the caterpillar exposed to the transgenic hybrid, by the age of the plant and by the insecticidal protein expressed by the Bt maize plant. First instar caterpillars are more susceptible than third caterpillars to the effects of Bt toxins, regardless of technology. Third instar larvae fed corn hybrids with PowerCoreTM, Herculex® and Optimum Intrasect® technologies have similar development to caterpillars fed on non-Bt maize.
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Palavras-chave
Lagarta-do-cartucho, Zea mays, Fall armyworm, Bt maize, Milho Bt, Resistência de plantas a insetos, Host plant resistance