Abstract
Background
Effective quarantine fumigation of raw logs remains a critical phytosanitary measure under international regulations such as ISPM 39. Methyl bromide (MB) and sulfuryl fluoride (SF) are widely used fumigants, yet their comparative behavior in high-moisture, tightly structured coniferous logs is poorly characterized. This study evaluated the sorption, penetration, and desorption dynamics of MB and SF in Pinus sylvestris var. mongolica logs to inform fumigant selection and optimize treatment protocols.
Results
Methyl bromide exhibited higher sorptive affinity than SF, as reflected by sustained declines in C/C₀ values over a 48 h exposure period. Concentration gradients showed MB was retained primarily in bark and phloem, with limited penetration beyond 2 cm. SF diffused more uniformly across depths up to 6 cm but remained at lower concentrations. Desorption patterns differed significantly. MB was rapidly released, particularly from surface tissues, whereas SF desorbed slowly with negligible release from xylem. Exponential model fitting revealed higher initial desorption rates and steeper decay for MB.
Conclusion
The two fumigants displayed distinct sorption–desorption–penetration profiles in P. sylvestris var. mongolica. MB demonstrated superior surface affinity and rapid desorption, making it suitable for targeting pests near the bark–cambium interface. SF achieved deeper diffusion but lower tissue concentrations, suggesting limited efficacy for short-duration treatments. These results highlight the importance of matching fumigant characteristics to pest location and substrate structure and provide a mechanistic basis for refining wood fumigation protocols in line with international phytosanitary standards.
