Environmental impacts of agricultural pest insects: five case studies reveal overlooked impact mechanisms and specify knowledge gaps

Invasive species can cause environmental impacts through various mechanisms. Assessing their impact can inform management decisions and illuminate risks to non-invaded areas. Research on the environmental impacts of invasive insects is heavily focused on a few well-known examples, with agricultural pests in particular receiving little attention. We aimed to investigate whether evidence for environmental impacts of insect pests of agriculture may be overlooked. We conducted in-depth literature reviews of three globally relevant insect agricultural pests– Halyomorpha halys , Helicoverpa armigera , and Spodoptera frugiperda . For comparison, we reviewed two forest pathogens known for their environmental impacts– Bursaphelenchus xylophilus and Phytophthora ramorum . We identified many published articles containing evidence of environmental impacts among the three insect agricultural pests that were not captured by existing reviews on invasive insects, with some demonstrating high levels of impact severity. Crucially, a preponderance of the identified articles did not directly address the findings in relation to environmental impacts. As expected, we recorded more conspicuous examples of environmental impacts among the case-study forest pathogens, though we also identified underappreciated impact mechanisms. We further provide evidence that supports the importance of considering management interventions as a key mechanism of non-target environmental impacts. This review raises awareness about the underreported environmental impacts of agricultural insect pests and specifies knowledge gaps that should guide future research.