Early Detection of Brown Rot Decay in Douglas-Fir and Southern Yellow Pine by Infrared Spectrophotometry

Samples of Douglas-fir heartwood and southern yellow pine sapwood were incubated with several brown rot rungi and examined for decomposition as shown by weight losses (to 10%). Warm-water extracts from the samples were analyzed by infrared spectrophotometry. An absorption peak at 1,720 cm -1 appeared in infrared spectra of decayed specimens but was not present in nondecayed specimens. As weight loss increased, the ratio of the absorbance at 1,720 cm -1 to the absorbance at 1,630 cm -1 increased. The ratio correlated with days of incubation and modulus of rupture.