2026/07/13 by Ronja Hausmann, Heinz Bußler, Sven Finnberg +8 · 2 voices
Agricultural and Biological Sciences · Environmental Science · #Forest Ecology and Biodiversity Studies #Forest Insect Ecology and Management #Ecology and Vegetation Dynamics Studies
paper · doi:10.1016/j.biocon.2026.112004
openalex publication_date 2026/07/13 · openalex created_date 2026/07/14 · openalex updated_date 2026/07/21
The management of forest insect outbreaks creates conflicts between the goals of pest control and biodiversity conservation. In oak stands, suppressing defoliating caterpillars and removing dying oaks to combat the jewel beetle Agrilus biguttatus can harm species dependent on oak microhabitats. We tested the effects of caterpillar suppression across a gradient of oak vitality on the abundance and presence of A. biguttatus , tree-related microhabitat (TreM) richness and the abundance, richness and presence of saproxylic and red-listed beetles. We assessed the vitality of 871 oaks annually for five years following a spongy moth ( Lymantria dispar ) outbreak, wherein half of the trees had been treated with the insecticide tebufenozide. Moreover, we evaluated the number of official indirect infestation signs (OPIS) to indicate pest species prevalence. We found that tebufenozide reduced the abundance of saproxylic beetles. With decreasing tree vitality, the presence, but not abundance, of A. biguttatus increased, whereas TreM richness and the abundance and richness of saproxylic and red-listed beetles strongly increased. The number of OPIS was associated with a higher abundance, but not presence, of A. biguttatus , as well as higher TreM and saproxylic beetle richness and abundance. Our results suggest that suppressing caterpillars with tebufenozide does not affect colonization by A. biguttatus , nor the richness of TreMs and beetles. Decreasing oak vitality promotes TreMs and saproxylic beetle richness, including red-listed species, but only weakly affects A. biguttatus . We therefore recommend reconsidering the view of dying oaks from a source of pests to an opportunity for saproxylic insect conservation.