Susceptibility of Spodoptera frugiperda (Lepidoptera: Noctuidae) field populations to the Cry1F Bacillus thuringiensis insecticidal protein
Keywords:
fall armyworm, resistance management, transgenic corn, Bt toxinAbstract
The fall armyworm, Spodoptera frugiperda (Smith & Abbot) (Lepidoptera: Noctuidae), is a polyphagous insect pest affecting multiple crops. Fall armyworm in corn is managed with insecticides and corn hybrids expressing insecticidal proteins derived from Bacillus thuringiensis Berliner (Bt). The early detection of insect resistance is important for making appropriate management decisions and for implementing integrated pest management and insect resistance management recommendations. The objective of this study was to estimate susceptibility of fall armyworm populations to the Cry1F Bt insecticidal protein, emphasizing collections from locations where fall armyworm overwinters in the U.S. Fall armyworm neonates were exposed to artificial diet treated with increasing Cry1F concentrations, and mortality and growth inhibition were evaluated after 7 d. Differences in Cry1F susceptibility between the most susceptible and the most tolerant field populations were 2- and 6-fold for 2012 and 2013, respectively. These results are consistent with other susceptibility studies of Bt toxicity in other species although reduced susceptibility in one population collected from Florida may suggest resistance development.
Resumo
A lagarta do cartucho, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), é uma praga polífaga que afeta várias culturas. A lagarta do cartucho no milho é controlada com o uso de inseticidas em milho híbrido que expressa proteínas com poder inseticida derivadas da bactéria Bacillus thuringiensis Berliner (Bt). A detecção precoce de casos de resistência em insetos é importante para decisões de manejo apropriadas e na implementação do manejo integrado de pragas e manejo de resistência de insetos. O objetivo desse estudo foi de estimar a susceptibilidade da lagarta do cartucho para a toxina Cry1F, enfatizando coletas de populações em diferentes locais dos Estados Unidos onde essa lagarta sobrevive durante o inverno. Neonatas da lagarta do cartucho foram expostas em dieta artificial tratada com aumento contínuo de concentrações da proteína Cry1F, e a mortalidade e a inibição de crescimento foram avaliados após 7 d da infestação. Diferenças entre a população de campo mais suscetível e a mais tolerante da lagarta do cartucho do milho foram 2 e 6 vezes em 2012 e 2013, respectivamente. Estes resultados são consistentes com estudos de susceptibilidade de Bt em outras espécies, embora a redução de susceptibilidade observada em uma população coletada na Florida possa sugerir o desenvolvimento de resistência.
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