Performance of Field-Collected Spodoptera frugiperda (Lepidoptera: Noctuidae) Strains Exposed to Different Transgenic and Refuge Maize Hybrids in Argentina

Abstract

Spodoptera frugiperda (J. E. Smith) is one of the major pests of maize in Argentina. The main tool for its control is the use of genetically modified maize hybrids expressing Bacillus thuringiensis (Bt) insecticidal proteins. Maize growers in Argentina initially controlled this pest with Bt maize that expressed a single Bt protein (Cry1Ab or Cry1F). Currently it is necessary to plant maize cultivars that produce two Bt proteins to achieve the satisfactory control. Recently, Cry1F field-evolved resistant populations of this species were confirmed in Argentina. The objective of this study was to evaluate the performance of S. frugiperda field-collected strains on different Bt and non-Bt maize hybrids. Strains were collected from non-Bt maize (T1), Agrisure TDMax (T2), Agrisure Viptera (T3), Agrisure Viptera 3110 (T4), Genuity VT Triple Pro (T5), and Power Core (T6). Three experiments were performed to 1) determine the survivorship and reproduction of field-collected larvae (F0) from Bt maize hybrids, 2) evaluate Cry1F resistance using an F1 screen, and 3) assess the performance of F1 strains on different maize hybrids. In the F0, the survivorship from larva to adult ranged from 0 to 63%. We obtained adults from only the T1, T2, T5, and T6 strains with no significant differences in the reproductive parameters. Continuously rearing F1 larvae on their collected hosts affected larval duration, which was significantly shorter for a known-laboratory Bt-susceptible strain than the field-collected strains. Our results support the existence of Cry1F-resistance alleles in S. frugiperda field populations in Argentina.

Susceptibility of the fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), to four species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) from Mizoram, North-Eastern India

“…The use of chemical insecticides is the most effective approach for the control of FAW (Belay et al 2012). However, the pest was reported to develop resistance against major classes of commonly used insecticides (Zhu et al 2015) and Cry proteins of Bacillus thuringiensis Berliner (Bacillaceae) as well (Murúa et al 2019); therefore, safer, eco-friendly control strategies need to be developed and further implemented. Biological control offers a promising strategy against a wide range of insect pests, and biopesticides being environmentally safer are potential alternatives to chemical pesticides.…”

Intercropped Bt and non‐Bt corn with ruzigrass (Urochloa ruziziensis) as a tool to resistance management of Spodoptera frugiperda (JE Smith, 1797) (Lepidoptera: Noctuidae)

“…This proves its efficiency in controlling even larger insects that may have migrated from ruzigrass plants and making it possible to recommend intercropping with this forage plant as an alternative refuge. Although there are already FAW populations that are resistant to Bt technology, 32,33,[69][70][71] transgenic corns that express the Vip3Aa20 protein in combination with other proteins still demonstrate synergism and a high control efficiency. [72][73][74] These cause high levels of mortality in susceptible and heterozygous larvae, even when initially fed with non-Bt corn for a period of 10 days, 65 and have a high effectiveness in the field.…”

“…26,29 In this way, exposure to toxins for a short period allows the survival of these insects, favoring resistance evolution. 30 In Brazil and other countries of the American continent, the existence of FAW population that is resistant to Bt toxins, such as Cry1Ab, 31 Cry1F, 32,33 and Cry2Ab2, 34,35 has already been documented. For the time being, the protein Vip3Aa20 remains effective in controlling this pest under field conditions, 36,37 but it urgently needs to be conserved through good management practices.…”

Transgenic Bt maize in South-and Central America: the pros and cons

“…Subsequent research on fall armyworm larvae collected from Bt transgenic maize fields and reserves confirmed a considerable decrease in the efficiency of Cry1F and showed an absence of efficiency in Cry-1Ab (Murúa et al, 2019).…”