Susceptibility of first instar Hippodamia convergens and Chrysoperla rufilabris to the insecticide sulfoxaflor

Authors

  • Rafael C. Aita University of Minnesota, Department of Entomology, 1980 Folwell Avenue, St. Paul, Minnesota 55108, USA
  • Anh K. Tran University of Minnesota, Department of Entomology, 1980 Folwell Avenue, St. Paul, Minnesota 55108, USA
  • Robert L. Koch University of Minnesota, Department of Entomology, 1980 Folwell Avenue, St. Paul, Minnesota 55108, USA

Abstract

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), continues to be the most economically important arthropod pest of soybean in the Midwest. Currently, management tactics for A. glycines rely on scouting and application of broad-spectrum insecticides. However, broadspectrum insecticides are toxic to most natural enemies of this aphid. Selective insecticides may provide an alternative strategy for suppressing A. glycines populations while conserving populations of its natural enemies. Therefore, the aim of this study was to evaluate the potential lethal and sublethal effects of sulfoxaflor (a relatively new selective insecticide), to 2 of this pest’s natural enemies, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae) and Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae). Laboratory bioassays were performed on first instars of both predators with residual toxicity evaluated over time until adult emergence. Parameters evaluated were mortality and developmental time for larvae and pupae, and adult body size. Fecundity also was determined for C. rufilabris. We found that sulfoxaflor was not toxic to first instar C. rufilabris. However, developmental time to adult was significantly delayed after exposure to this insecticide, but fecundity and body size were not negatively affected. For H. convergens, sulfoxaflor at 25% of the field rate was toxic to first instars. No significant differences were found with regard to developmental time and body size. It is important to note that sulfoxaflor, though relatively less toxic than some insecticides, is not entirely without consequence if natural enemies are exposed. The present study emphasizes the importance of examining earlier life stages and potential sublethal effects when evaluating the toxicity of insecticides in the presence of natural enemies.

 

Resumo

O pulgão da soja, Aphis glycines Matsumura (Hemiptera: Aphididae), continua a ser o inseto-praga de maior importância econômica da soja no Centro-Oeste americano. Atualmente, as técnicas de manejo de A. glycines dependem da amostragem e aplicação de inseticidas de amplo espectro. No entanto, inseticidas de amplo espectro são tóxicos para a maioria dos inimigos naturais deste pulgão. Inseticidas seletivos podem fornecer uma estratégia alternativa para suprimir as populações de A. glycines, conservando populações de seus inimigos naturais. Portanto, o objetivo deste estudo foi avaliar os potenciais efeitos letais e subletais do sulfoxaflor (um inseticida seletivo relativamente novo) a 2 dos inimigos naturais desta praga, Chrysoperla rufilabris (Burmeister) (Neuroptera: Chrysopidae) e Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae). Ensaios de laboratório foram realizados nos primeiros ínstares de ambos os predadores, com toxicidade residual avaliada ao longo do tempo até a emergência dos adultos. Os parâmetros avaliados foram mortalidade e tempo de desenvolvimento de larvas e pupas, e tamanho dos adultos. Fecundidade também foi determinada para C. rufilabris. Encontramos que sulfoxaflor não foi tóxico para o primeiro ínstar de C. rufilabris. Entretanto, o tempo de desenvolvimento até a fase adulta foi significativamente maior após a exposição a este inseticida, porém fecundidade e tamanho dos adultos não foram negativamente afetados. Para H. convergens, 25% da dose recomendada de sulfoxaflor foi tóxico para os primeiros ínstares. Não foram encontradas diferenças significativas em relação ao tempo de desenvolvimento e tamanho dos adultos. É importante ressaltar que sulfoxaflor, embora relativamente menos tóxico que alguns inseticidas, ainda apresenta consequências negativas se inimigos naturais forem expostos. O presente estudo enfatiza a importância de se examinar os estágios iniciais de desenvolvimento do inseto e possíveis efeitos subletais ao avaliar-se a toxicidade de inseticidas na presença de inimigos naturais.

Key Words: integrated pest management; natural enemies; selective insecticides; soybean aphid

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Published

2020-07-09

Issue

Vol. 103, No. 2 (June 2020)

Section

Research Papers

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