Two Decades of Monitoring Tortrix viridana and Associated Oak-Defoliator Groups in the Republic of Moldova

Long-term phytosanitary monitoring provides essential information on temporal changes in forest-insect populations, but conclusions depend on consistent sampling and accurate definition of the taxa included in the analysis. We examined the dynamics of Tortrix viridana L. (Lepidoptera: Tortricidae) and two associated operational groups, other Tortricidae and Pyralidae, in Quercus robur L. stands at Molești–Răzeni and Tigheci–Cociulia in the Republic of Moldova. Monitoring covered the 2005–2025 calendar interval and provided 20 annual larval observations per site; larval data were unavailable for Molești–Răzeni in 2015 and for Tigheci–Cociulia in 2014 because of phytosanitary treatments. Annual larval densities showed pronounced interannual variability and distinct site-specific peaks. Other Tortricidae had the highest mean larval density at both sites, whereas T. viridana represented a smaller and temporally variable component of the three-group assemblage. After correction for temporal autocorrelation and multiple testing, significant decreasing trends in T. viridana and Pyralidae larval densities were detected at Molești–Răzeni, whereas no focal group showed a significant temporal trend at Tigheci–Cociulia. The results do not support a uniform regional decline of T. viridana or any other focal group. Instead, they demonstrate spatially heterogeneous population dynamics and show that operational forest surveillance should consider multiple defoliator groups rather than relying exclusively on T. viridana.