ABSTRACT A 6-year field monitoring study was designed to compare the presence of fall armyworm Spodoptera frugiperda (J. E. Smith), leaf injury, its parasitoids, 100 seed weight, and seed yield of Bt maize hybrids approved for commercialization in the Brazilian market. Field trials were planted in two municipalities, divided into two periods, from 2011 to 2014 (period I), and due to the approval of different Bt hybrids, from 2015 to 2016 (period II). Treatments were Bt, non-Bt maize and all non-Bt maize sprayed with insecticide methomyl. Six Bt-maize hybrids were planted, expressing the following proteins: Cry1Ab, Cry1F, Cry1A.105 (Cry1Ab +Cry1Ac +Cry1F), Cry2Ab2a and Vip3. In 2015 and 2016 Bt Powercore was planted due to its commercial approval. The number of S. frugiperda larvae for most Bt hybrids was lower than on non-Bt hybrids, except for Fórmula TL and Herculex in period II, in both municipalities. In period I, Bt hybrids VT, VT 2 and Viptera showed almost no injury on their leaves, despite the high number of fall armyworm larvae found in plants. Different parasitoids emerged from larvae from Bt and non Bt hybrids: Archytas sp., Campoletis sp., Chelonus sp., Eiphosoma sp. and Ophion luteus. The average 100 seed weight was higher in municipality from Sete Lagoas for all Bt hybrids, non-Bt hybrids and non-Bt hybrids sprayed with methomyl, when compared to Nova Porteirinha during period I. Fórmula TL, non-Bt Fórmula TL sprayed with methomyl, and non-Bt Fórmula TL showed the lowest seed yield in both municipalities and periods.

O objetivo deste trabalho foi avaliar parâmetros biológicos da lagarta-do-cartucho do milho (Spodoptera frugiperda), alimentada com híbridos de milho Bt, que expressam a toxina Cry 1A(b), e com seus respectivos isogênicos não Bt. Os experimentos foram realizados no laboratório da Embrapa Milho e Sorgo, em Sete Lagoas, MG. Os parâmetros avaliados foram: sobrevivência de larvas após 48 horas, sobrevivência da fase larval e pré-imaginal, biomassa de larvas aos 14 dias de idade, biomassa de pupas, período de desenvolvimento larval, e não preferência alimentar de larvas do primeiro ínstar. Larvas de S. frugiperda apresentam menor sobrevivência nas primeiras 48 horas de alimentação e durante toda a fase larval, na maioria dos híbridos de milho Bt, em comparação ao milho não Bt. A biomassa de larvas e pupas foi sempre menor no milho Bt, e o período larval e o pré-imaginal, maior. Houve interação entre a toxina Cry 1A(b) e a base genética dos híbridos transgênicos, quanto à sobrevivência e à biomassa larval. Larvas recém-eclodidas de S. frugiperda apresentam preferência pela alimentação em milho não Bt.

The objective of this work was to evaluate biological parameters of maize fall armyworm (Spodoptera frugiperda) fed with Bt maize hybrids expressing the Cry 1A(b) toxin, and with its isogenic non-Bt hybrids. The experiments were carried out in the laboratory of Embrapa Milho e Sorgo, Sete Lagoas, MG, Brazil. The parameters evaluated were: survival of larvae after 48 hours, survival of larval and preimaginal phases, larvae biomass at 14 days of age, pupae biomass, larval development period, and feeding non‑preference of first instar larvae. Larvae of S. frugiperda show less resistance in the first 48 hours of feeding and during the entire larval phase in most Bt maize hybrids, in comparison to non-Bt maize. The biomass of larvae and pupae developed in Bt maize was always smaller, and the larval and preimaginal period were longer. There was interaction between the Cry 1A(b) toxin and the genetic base of the transgenic hybrids regarding survival and larval biomass. Newly hatched S. frugiperda larvae show preference for feeding on non-Bt maize.