Manejo de lepidópteros-praga na cultura do milho com o evento Bt piramidado Cry1A.105 e Cry2Ab2

Abstract

Resumo -O objetivo deste trabalho foi avaliar a eficácia do evento piramidado (MON 89034), que expressa as proteínas Cry1A.105 e Cry2Ab2, no controle dos principais lepidópteros-praga da cultura do milho no Brasil, Spodoptera frugiperda, Helicoverpa spp. e Diatraea saccharalis. Os ensaios foram conduzidos em quatro regiões do país, com o híbrido DKB 390, submetido a seis tratamentos: híbrido com o evento piramidado, híbrido com o evento que expressa apenas a proteína Cry1A(b) (MON 810) e híbrido convencional (não Bt), todos com e sem manejo integrado de S. frugiperda. Para o evento piramidado, não foi necessário o controle químico em nenhum dos locais avaliados. Diferenças significativas foram observadas entre os tratamentos quanto aos danos e à presença de lagartas. Em geral, essas variáveis foram mais baixas no híbrido com o evento piramidado e mais altas no híbrido convencional, sem controle químico. Sob alta infestação, o controle químico reduziu os danos causados por S. frugiperda e D. saccharalis, tanto no evento que expressa apenas uma proteína, como no híbrido convencional. Com base nos danos causados pelos insetos, o evento piramidado Cry1A.105 e Cry2Ab2 é eficiente no controle dos principais lepidópteros-pragas do milho no Brasil.Termos para indexação: Helicoverpa, Zea mays, broca, lagarta-da-espiga, lagarta-do-cartucho, manejo integrado. Management of Lepidopteran pests in maize crop using the Bt pyramided event Cry1A.105 and Cry2Ab2Abstract -The objective of this work was to evaluate the efficacy of the pyramided event (MON 89034), expressing Cry1A.105 and Cry2Ab2 proteins, in the control of the main lepidopteran maize pests in Brazil, Spodoptera frugiperda, Helicoverpa spp., and Diatraea saccharalis. The trials were conducted in four regions of the country, using the hybrid DKB 390, subjected to six treatments: hybrid containing the pyramided event, hybrid expressing only the protein Cry1A(b) (MON 810), and conventional hybrid (non Bt), all with and without integrated management for S. frugiperda. For the pyramided event, chemical control was not necessary in any of the evaluated locations. Significant differences were observed between treatments for larval damage and presence. In general, those variables were lower for the pyramided hybrid and higher for the conventional hybrid without chemical control. Under high infestation, chemical control reduced the damage caused by S. frugiperda and D. saccharalis both on the single protein event and on the conventional hybrid. Based on the damage caused by the insects, the pyramided event Cry1A.105 and Cry2Ab2 is efficient in the control of the main lepidopteran maize pests in Brazil.

Cross-Resistance between Cry1 Proteins in Fall Armyworm (Spodoptera frugiperda) May Affect the Durability of Current Pyramided Bt Maize Hybrids in Brazil

“…This result was expected due to the known lower activity of Cry1Ab (MON 810) against S . frugiperda [ 23 ]. The maize products expressing Cry1F (TC1507) and Cry1Ab (MON 810) proteins had no effect on the survival or growth of the RR strain ( Table 5 ; S5 Table ).…”

“…Bt maize hybrids have been useful in controlling S . frugiperda in Brazil [ 21 – 23 ]. Despite the economic benefits provided by Bt crops [ 24 ], the continuous expression of cry genes in Bt plants imposes a strong selection pressure for resistance in target pest populations [ 25 ], and the benefits of Bt crops would be reduced when insect pests evolve resistance [ 26 ].…”

Field‐evolved resistance to Cry1Ab maize by Spodoptera frugiperda in Brazil

“…The considerable economic losses caused by FAW to maize plants led growers to rely on rigorous management based on the use of chemical insecticides, contributing to the evolution of resistance to most of those chemicals . In 2008, MON 810 maize expressing the Cry1Ab protein from Bacillus thuringiensis ( Bt ) was the first Bt maize technology deployed in Brazil and provided significant levels of control against FAW . Thereafter, different Bt maize technologies were launched, targeting FAW in Brazil, reaching up to 80% penetration in the maize‐growing areas during cropping season 2014…”

“…Even though MON 810 maize has contributed to integrated pest management (IPM) in Brazil, it is not a high‐dose product for FAW primarily owing to the moderate activity of Cry1Ab against this species . The relatively moderate activity of Cry1Ab against FAW, in combination with a tropical/subtropical environment that allows multiple maize‐growing seasons and low compliance with non‐ Bt refuge recommendations, poses a risk of resistance evolution to MON 810 in FAW.…”

EFICÁCIA DE TECNOLOGIAS DE MILHO Bt NO MANEJO DE LEPIDÓPTEROS-PRAGAS

“…O uso da tecnologia Bt no milho tem se destacado como uma das principais ferramentas no manejo dessas pragas. Diversos autores relataram a eficácia e os benefícios do milho Bt no manejo de pragas na cultura do milho (Edgerton et al, 2012;James, 2014;Klümper & Qaim, 2014;Michelotto et al, 2011;Waquil et al, 2013). Além disso, foi verificado rendimento de grãos superior na ordem de 32% em alguns eventos de milho Bt quando comparado a híbridos convencionais (Waquil et al, 2002).…”