Brown Root Rot of 10 Species of Fruit Trees Caused by Phellinus noxius in Taiwan.

Abstract

Wilt and death of fruit trees was surveyed from 1990 to 1996. Most trees with decline symptoms in central and southern Taiwan had brown root rot caused by Phellinus noxius. The infected trees included litchi, sugar-apple, plumum, pear, loquat, persimmon, carambola, wax apple, grape, and jellyfig, with ages ranging from young seedlings up to 10-year-old trees. Symptoms were leaf discoloration, unthrifty appearance, and eventual death. Upon inoculation of the roots with P. noxius grown in a wheat-oat medium, healthy seedlings of these 10 tree species were killed. P. noxius was reisolated from diseased tissues of inoculated roots. The isolates of P. noxius obtained from different hosts were similar in morphological characteristics. Host specificity among the tested isolates was not observed in the cross-inoculation test, but variability in virulence was noted in some tests. Mycelial growth of different isolates of P. noxius showed similar temperature response, but the growth rates varied dramatically. Fruiting bodies were rarely found in the field. However, the fungus produced fruiting bodies artificially, on a sawdust medium, that were similar to those produced on the lower stems of declining trees. Brown root rot can be induced by replanting seedlings in infested soil or by contact with the diseased or dead roots. P. noxius causing brown root rot of these 10 fruit trees has not been previously reported.