The hidden cost of plant protection through systemic insecticides: Balancing pest control with the safeguarding of non-target pollinators

Invasive insect pests present escalating threats to agricultural productivity and environmental stability, often necessitating the intensive use of broad-spectrum insecticides that jeopardize non-target organisms and ecosystem services. Endotherapy (i.e. trunk injection) is increasingly proposed as a sustainable alternative to conventional sprays to minimize environmental dispersion and reduce off-target impact. In the present study, we used the highly polyphagous Japanese beetle Popillia japonica, a quarantine priority pest in EU due to its significant economic and environmental risks, as a model to evaluate the ecological trade-offs of systemic pest management. We assessed the efficacy of three active ingredients, acetamiprid, abamectin, and emamectin benzoate, in controlling the invasive pest. The compounds were injected into linden trees, Tilia spp., at the resumption of vegetative growth, and their translocation to floral tissues was quantified to determine potential risks to the non-target honey bee, Apis mellifera. Results indicate that while acetamiprid provided effective control of adult beetles, its residues detected in flowers significantly reduced honey bee survival and altered feeding behavior in a dose-dependent manner. Crucially, sublethal concentrations of both acetamiprid and abamectin impaired bee cognitive performance, highlighting hidden costs often overlooked in standard ecotoxicity assessments. These findings underscore that the perceived safety of endotherapy is contingent upon active ingredient selection and application timing relative to blooming. Our work demonstrates the necessity of evaluating systemic treatments within a sustainability-oriented framework that balances immediate pest suppression with the long-term safeguarding of pollination services. Such integrated approaches are essential for aligning agricultural practices with global mandates for pesticide reduction and biodiversity conservation.