The suppressive effect of wood ants on bark beetle colonization

Abstract

Climate change supports bark beetle outbreaks in European forests, posing a significant threat to the economically important Norway spruce (Picea abies). While chemical control methods in pest control are increasingly restricted, biological control using natural enemies, such as wood ants (Formica spp.), offers a sustainable alternative. Despite their known role as generalist predators of various forest pests, the direct impact of wood ants on bark beetle colonization remains underexplored. This study investigated the suppressive effect of Formica rufa ants on six-toothed spruce bark beetle (Pityogenes chalcographus) colonization. Branch traps were installed near 34 wood ant nests across five localities in Czechia. At each nest, one trap was placed 1 meter from the nest (treatment) and another 40 meters away (control). In total, traps near ant nests showed a mean reduction of approximately 40% in beetle colonization. Results confirmed similar suppressive metrics, consistent across all study localities. Our findings demonstrate that ants significantly suppress bark beetle colonization. This confirms the crucial role of wood ants as biological control agents against bark beetle damage and supports their integration into sustainable forest management strategies.