Electrocution of Japanese Knotweed (Reynoutria japonica Houtt.) Rhizome Sprouts Under Controlled Conditions: Implications for Forest Management

Invasive weeds threaten forest ecosystem sustainability worldwide, underscoring the need for non-chemical management strategies. To address this challenge, the present study investigated the short-term morphological response and survival of the Japanese knotweed (Reynoutria japonica Houtt.) rhizome sprouts subjected to 60-s electrocution at 0–180 V in 20-V increments. The one-way ANOVA showed no significant effect on sprout diameter (p > 0.05), whereas sprout length varied significantly (p < 0.05; η2 = 0.540), with Tukey’s HSD post-hoc test revealing that mean sprout length ranged from 20.9 ± 2.1 cm to 42.6 ± 4.6 cm for sprouts subjected to 60 V and 180 V, respectively. In contrast, the Mantel–Cox trend test indicated a significant decline in sprout survival time with increasing voltage (χ2(1) = 29.028; p < 0.001), as reflected by the Kaplan–Meier analysis. Furthermore, the Cox proportional hazards model showed a 2.60% increase in mortality hazard per 1-V increase (HR = 1.026; p < 0.001). These results indicate that electrocution treatments of ≥100 V induce rapid sprout mortality, with complete mortality observed by day 3 at 100 and 180 V and by day 4 at 120–160 V, a response descriptively referred to as the “flash-kill” effect, and highlight survival analysis as a more informative indicator for evaluating R. japonica electrocution efficacy. Nevertheless, even though short-term sprout mortality is not a definitive measure of control, a long-term evaluation must account for rhizome reserve depletion, bud number and viability, as well as sprout reemergence under forest-oriented, field-scale studies.