Eficácia de milho transgênico tratado com inseticida no controle da lagarta-do-cartucho no milho safrinha no estado de São Paulo, Brasil

Abstract

Several genetically modified maize events expressing insecticidal proteins from Bacillus thuringiensis (Bt) have been commercially available in Brazil, intended to control of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae). The objective of this study was to evaluate the efficiency of transgenic (Bt) and conventional (non-Bt) hybrids in the control of fall armyworm, treated or not with insecticides throughout three late growing seasons. To this end, trials were conducted at three locations in the state of São Paulo, in a randomized complete block design, in factorial arrangements with 5x4, 5x4 and 8x4 factors, respectively. The first factor consisted of the number of commercial hybrids of different companies. The second factor was represented by the different control managements of insect (non-Bt hybrid with and without insecticide; Bt hybrid with and without insecticide). The damage caused by fall armyworm was evaluated on a visual 1-9 scale, from score 0 (no damage) to 9 (totally destroyed whorl), and grain yield (kg ha -1 ). The data were analyzed by analysis of variance and the means compared by the Tukey test at 5% probability for each parameter evaluated at each location. For the Bt hybrids, the damage scores attributed to fall armyworm were lower and the proteins Cry 1F, Cry 1A105 and VIP3Aa20 were the most efficient in reducing leaf damage. Insecticide applications proved efficient in reducing leaf damage caused by the pest. Application of insecticides to Bt hybrids generally reduced leaf damage, especially for Cry1Ab-producing hybrids, which were the least effective in reducing pest damage without insecticides.Index terms: Zea mays; Spodoptera frugiperda; pest management. RESUMODiversas tecnologias de milho geneticamente modificado (Bt) foram liberadas comercialmente desde 2007 visando principalmente o controle da lagarta-do-cartucho, Spodoptera frugiperda (Lepidoptera: Noctuidae). O objetivo deste trabalho foi avaliar a eficiência de híbridos transgênicos (Bt) e convencionais (não Bt) no controle lagarta-do-cartucho, submetidas ou não a inseticidas. Para isso, foram conduzidos ensaios em três localidades do estado de São Paulo nas safrinhas de 2009, 2010 e 2011, com delineamento experimental de blocos casualizados, em esquema fatorial 5x4, 5x4 e 8x4, respectivamente. O primeiro fator correspondeu ao número de híbridos comerciais de diferentes empresas. O segundo fator foi constituído pela utilização de diferentes manejos de controle do inseto. Para a avaliação dos danos ocasionados pela lagarta-do-cartucho, foram realizadas amostragens ao acaso de 20 plantas por parcela, aplicando-se uma escala de notas visuais, atribuindo notas que variam de 0 (sem dano) a 9 (cartucho totalmente destruído) e obtido a produtividade de grãos. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Tukey a 5% de probabilidade, para cada parâmetro avaliado em cada localidade. Os híbridos transgênicos proporcionaram redução nas notas de danos atribuídas a lagarta-do-cartu...

Streamlining leaf damage rating scales for the fall armyworm on maize

“…The "Davis' 0 to 9 whorl & furl damage scale for fall armyworm" (Table 2) (Davis et al 1992) is of the ordinal data type, and ranks damage in combination with frequency and severity information. It is historically and currently the most used leaf damage scale for the fall armyworm (Wiseman et al 1996;Davis et al 1996;Williams et al 1999;Lynch et al 1999aLynch et al , 1999bRea et al 2000Rea et al , 2002Buntin et al 2001, 2004, Buntin 2008Michelotto et al 2017;Lourenço et al 2017;Sisay et al 2019a;Vassallo et al 2019;Nboyine et al 2020;Teixeira Silva et al 2020). It has been particularly used to assess resistance levels of maize hybrids to fall armyworm feeding.…”

Comparison of Ear Damage Caused by Caterpillar Pests in Transgenic (Bt) Maize Hybrids and Conventional Maize Hybrids

“…zea damages in three out of the four experimental fields that were evaluated, and also the findings of Michelotto et al (2017b), when assessing the efficiency of the Maximus Viptera hybrid (Vip3Aa20) in the reduction of S. frugiperda Table 7 -Score for ear damage caused by caterpillars for each hybrid and technology of location in the state of São Paulo, in the summer crop (2010/11).…”

“…The first event characterized by expressing the insecticidal protein was Cry 1Ab. Since then, other events with expression of different insecticidal proteins and even with more than one protein were commercially released for the control of insects of the order Lepidoptera (Michelotto et al, 2017b;CNTBio, 2018). Nowadays, among Bt toxins that attack lepidopteran pests, the following stand out:…”

“…However, there are few studies carried out in Brazil that compare the efficiency of the different Bt technologies in the control of caterpillar pests in maize ears. Moreover, damages caused by maize pests differ even among conventional cultivars (Ota et al, 2011;Moraes et al, 2015 andMichelotto et al, 2017b). Therefore, the hypothesis is that transgenic maize technologies can present variation in regard to damages caused by the corn earworm, depending on the variability among the hybrids when expressing toxins.…”

Efficacy of Insecticides Against Spodoptera frugiperda (Smith, 1797)

“…Thus, the control of this insect has demanded a high number of insecticide applications, causing populations resistant to the different products (Diez-Rodríguez & Omoto, 2001;Ahmad et al, 2018;Wang et al, 2018), as well as negative implications for the environment (Michelotto et al, 2017). (Cruz, 2002).…”