Voltage over herbicides: defining lethal electrocution thresholds for successful eradication of Ailanthus altissima (Mill.) Swingle seedlings

The tree-of-heaven (Ailanthus altissima (Mill.) Swingle) is a highly aggressive invasive arboreal species that causes severe ecological damage in forest ecosystems worldwide. Traditional management relies heavily on cutting, which triggers vigorous resprouting, and on herbicides that pose ecotoxicological risks, thus necessitating effective, non-chemical alternatives such as electrocution. This study quantified lethal electrocution thresholds required to induce complete seedling mortality. Seedlings (n = 3 per exposure) were subjected to electrocution at 20 V and 40 V treatments across 10 exposure intervals. Voltage was regulated using an autotransformer and applied via the anode connected to the seedling base, while a grounded metal plate served as the current return path. Survival patterns showed a clear, duration-dependent response over the nine-day monitoring period. The Mantel-Cox test revealed a highly significant difference in survival across exposure durations for both the 20 V (χ²₍₂₎ = 40.69, p < 0.001) and 40 V (χ²₍₂₎ = 32.31, p < 0.001) treatments. The subsequent Kaplan-Meier survival analysis and hierarchical cluster analysis identified three distinct physiological response zones: (i) tolerance zone (0–30 min) with high survival; (ii) transitional threshold zone (1–3 h) marking progressive decline in survival; and (iii) critical lethality zone (4–6 h) causing rapid mortality within three days at 40 V. The pairwise Mantel-Cox comparisons with the Holm-Bonferroni correction revealed key insights. Notably, survival in the 40 V intermediate treatment (1–3 h) was statistically indistinguishable from that observed in the 20 V high-duration treatment (4–6 h) (p = 0.520). These findings suggest that increasing the voltage to 40 V may halve operating time while maintaining comparable eradication efficacy and preventing resprouting. Collectively, these results provide an initial baseline for precision electrocution as an eco-friendly management strategy for A. altissima that can be integrated into existing management frameworks in forest-sensitive areas.