Identifying White Oak Logs with Sodium Nitrite

Because red oak logs can spread oak wilt, the European Economic Community (EEC) requires that all oak logs imported from the eastern United States where oak wilt is found must be fumigated. However, a Common Market Commission has indicated that logs of white oak may be exempt from fumigation if a reliable method for identifying white oak from other species has been developed for use by officials at the ports of unloading. We found that spraying a 10 percent solution of sodium nitrite on the heartwood of oak logs is a simple color test that unerringly separates the eastern U.S. red oaks from the white oaks. To confirm the accuracy of this chemical identification test, we tested nearly 10,000 oak logs at 30 sawmills throughout the eastern United States. In, addition, we tested nearly 500 eastern oak specimens and all commercially important eastern hardwoods and softwoods from the Forest Products Laboratory wood collection. In every test on oak heartwood, the sodium nitrite indicated the correct species group. Of the other species, only chestnut (Castanae) and occasionally chinkapin (Castanopsis) reacted like white oak. As with nearly all chemical reactions, temperature affects the reaction time and development of diagnostic color.

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