Side Effects of Single-Transgene or Pyramided Genetically Modified Maize on the Generalist Endoparasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

Abstract

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is an agricultural pest native to tropical and subtropical regions of the Americas, with considerable potential for global invasion and seasonal migration. Although genetically modified (GM) plants have shown positive impacts on the economy and the environment as they synthesize proteins that act as natural insecticides and are primarily intended to protect the crops from damage by specific pests, potential effects of Bt toxins on non-target organisms can occur. This experiment aimed to evaluate the potential impacts on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae), using the pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) as hosts, which were fed with transgenic maize genotypes such as Herculex®, expressing Cry1F protein, and PowerCore®, expressing Cry1F, Cry1A.105, and Cry2Ab2 proteins, or their non-transgenic isohybrid. The experiment was conducted in a completely randomized design with ten replicates. Spodoptera frugiperda larvae were fed ad libitum with transgenic and non-transgenic maize until the pupal stage and then individually exposed to six P. elaeisis females for 78 h. The total number of adults, emerged males, tibia size, cephalic capsule size, and parasitoid body size were not influenced by host feeding. However, the number of emerged females from the Herculex® and PowerCore® treatments was lower than that for the isohybrid treatment. The sex ratio and longevity of parasitoids emerging from PowerCore® were 1.05 and 1.26 times lower, respectively, than that of those from the isohybrid. Furthermore, the number of dead P. elaeisis within the host pupa was 10.56 times higher in the PowerCore® genotype. Combining Bt proteins within pyramided genotypes should cause minimal impacts and promote the conservation and integration of beneficial insects. The results of this study provide helpful information for developing effective and compatible integrated pest management (IPM) strategies.