Methanol extracts from black locust (Robinia pseudoacacia), osage oran
ge (Maclura pomifera), redwood (Sequoia sempervirens), and Intsia biju
ga heartwood were used to increase the decay resistance of aspen (Popu
lus tremuloides) blocks. At a 10 percent retention level, treated aspe
n blocks exposed to a brown-rot fungus showed a weight loss decrease o
f 95 percent.