Lifecycle of the invasive omnivore, Forficula auricularia, in Australian grain growing environments

Abstract

Background: The European earwig, Forficula auricularia (L.) (Dermaptera: Forficulidae), is regarded as an important beneficial in many orchard environments but has the potential to be a plant pest in other systems, including to grain crops. Due to its agricultural importance, the lifecycle of F. auricularia has been widely studied in North America and Europe. However, much less is known in the southern hemisphere, including Australia where F. auricularia has been present for over 170 years.

Results: To elucidate the lifecycle of F. auricularia, we monitored five sites in grain-growing areas of southern Australia using two different trap types. Adults were found year-round, but most prevalent from late-spring to mid-winter. First instars were typically found from mid to late winter. Second, third and fourth instars occurred from winter through to late spring. The seasonal development of F. auricularia in Australia may be much earlier than observed in comparable North American studies. Degree day modelling highlights variation in development times across the active season for F. auricularia across our sites.

Conclusion: Forficula auricularia is well adapted to the Australian grain growing environments. The timing of egg hatching aligns closely with crop emergence, juveniles then develop alongside the crop, and adult development occurs by harvest time in late spring. These findings are important given that many of these crops (canola, lucerne, pulses) are vulnerable to attack by F. auricularia during emergence and development. They also suggest a phenotypic capacity of this species to adapt different phenology after introduction into a novel environment. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: Australia; European earwig; agriculture; grain crops; phenology.

Figure 1

Map of Australia showing the location, climatic data and crop type at each field site used in this study.

Figure 2

Log mean abundance of Forficula auricularia juveniles (all instars combined) collected from the three trap types at each field site. Total individuals for each site are: Elmore = 3190, Thoona = 3162, Manoora = 3582, Milang = 1459, Finniss = 3661. Error bars show the range of the data. Note different scales used for each site.

Figure 3

Log mean abundance of Forficula auricularia adults collected from the three trap types at each field site. Total individuals for each site are: Elmore = 8473, Thoona = 1731, Manoora = 1150, Milang = 319, Finniss = 696. Error bars show the range of the data. Note different scales used for each site.

Figure 4

Generalized phenology of Forficula auricularia in south‐eastern Australia (all years, sites and trapping methods combined). The proportions shown are the mean proportions across field sites and years for each month.

Figure 5

Day degree models for Forficula auricularia run at each sampling date that held an observation of a first instar. Circles depict the presence of each juvenile life stage collected at each sampling point. Lines represent a single model output and depict the first date at which each life stage was predicted in the models.