The role of understory structural complexity in Cydalima perspectalis outbreak dynamics in west Georgian forests

Abstract

In forest ecosystems, the understory represents a fundamental structural layer that plays a decisive role in regulating
microclimates and maintaining biological equilibrium. This study examines the influence of invasive and aggressive native spe
cies on the structural transformation of the understory and analyzes how this complexity affects the outbreak dynamics of the
box tree moth (Cydalima perspectalis) in Georgian forests. Field monitoring conducted between 2023 and 2025 across study areas
in the Adjara and Guria regions confirms that the dense, multi-layered understory formed by the invasive Amorpha fruticosa
and the native Smilax excelsa functions as a vital ecological refugium for the pest. The findings demonstrate that high understory
structural complexity maintains relative humidity, creates a windbreak barrier, and provides thermal insulation, significantly
increasing the survival rate of overwintering C. perspectalis larvae. Statistical analysis revealed a strong correlation between
understory density and the intensity of damage in native boxwood (Buxus colchica) stands. The study concludes that effective
pest management strategies must account for understory structural characteristics, as this is critical for the natural regeneration
of boxwood groves and the long-term resilience of forest ecosystems.