Branch sections of camphor (Cinnamomum camphora) inoculated with tree brown rot
disease Phellinus noxius were used as tracers for indicating the survival of P. noxius in soil,
and hence for evaluating of the effect of chemical treatments. These indicators were buried
at 5, 30, and 50 cm in depth of different experimental blocks of soil in the field, and 25%
Prochloraz (E.C.), 25% Prochloraz (E.W.), 25% Triadimefon (W.P.), 24.9% Difenoconazole
(E.C.), and the essential oil of Cinnamomum osmophloeum in 1000-fold dilutions were gently
irrigated into different experimental blocks, with irrigation with water used as the control
group. An experimental block of fumigation with the registered 98% Dazomet (G.R.) was
applied for comparison. Branch tracers were collected, cleaned, and cultured with selective
medium (MA+4) for P. noxius after 14 d. Re-isolation numbers of tracers with P. noxius in
a total of 5 tracers buried at 5, 30, and 50 cm in depth of experimental blocks under each
treatment were as follows: 3, 3.25, and 2 for Prochloraz (E.C.); 1.75, 2.5, and 1.25 for Prochloraz
(E.W.); 2.75, 4.25, and 1.5 for Triadimefon; 3.5, 2.75, and 1.25 for Difenoconazole;
1.75, 2.5, and 1.75 for essential oil of C. osmophloeum; 2.75, 1.25, and 2.25 for the water
control; and there was no re-isolation with Dazomet fumigation. Moreover, P. noxius could
be re-isolated from all tracers after direct immersion for 1, 24, and 48 h in 1000-fold dilutions
of Prochloraz (E.C.), Prochloraz (E.W.), Triadimefon, Difenoconazole, and the essential
oil of C. osmophloeum. Results indicated that the tested chemicals have limited effects
of inhibiting P. noxius in soil.