Iodomethane as a methyl bromide alternative for prevention of non-microbial enzyme stain (gray stain) of hardwoods by log fumigation

Non-microbial discolorations of sapwood in hardwoods causes large economic loss. One method of prevention is to fumigate fresh logs with methyl bromide. Iodomethane has been suggested as a substitute for ozone-depleting methyl bromide in agricultural applications, but its ability to prevent enzyme-mediated stain in wood has not been demonstrated. Sugar hackberry and red oak logs were fumigated under plastic taps with iodomethane and processed into lumber. Good control of gray stain was noted for hackberry but not for red oak. Iodomethane does kill parenchyma in the sapwood, but is not an adequate substitute for methyl bromide for stain prevention in these hardwoods at similar concentration x time product (CT) values (approximately 18,000 g-hr.). Further trials are needed to determine efficacy of methyl iodide at higher CT values (equivalent molal basis to methyl bromide). Reduction of log fumigation time from 72 to 48 hours with methyl bromide does not provide adequate prevention of sapwood discolorations in these hardwoods.

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