Control Experiments with some Fungicides for the White Root Rot of Tea (Rosellinia necatrix (HART.) BERL.)

Abstract

1. Soil sterilization was carried out using 3 fungicides in tea field where white root rot of tea was occurring.Chloropicrin (applied 20 ml. per (50cm.)2 of the field) showed an excellent controlling power of the disease, but other two organomercuric fungicides did not show any effectiveness.2. Growth of mycelium from diseased tea roots was nearly inhibited when the roots were dipped in the solutions of two organomercuric fungicides for 10-30 minutes.No inhibitory effect on the growth of mycelium was found when the fungicides were applied in the soil in which the roots were buried.3. In fields and pots, the fungicides were applied in soil in which diseased tea roots were buried. The fungicidal effect on the fungus in diseased tea root was examined in two ways: one was the examination of the growth of myceliumfrom the treated tea roots and the other was inoculation test with the roots against tea seedlings.In pot test, chloropicrin and "Dorokurô"ru" (chloropicrin 80%) inhibited the growth of mycelium from the diseased roots completely, but a slight disease was occurred only when applied with 4 ml. of "Dorokurôru" per pot (diam. 30 cm.).In field test, no fungicides inhibited growth of mycelium completely, but the disease occurrence was very slight in chloropicrin treatment [applied 3 or 6 ml. per (50cm.)2 of the field]4. From the results of these control experiments, chloropicrin was found to be practically available for the control of white root rot of tea."Dorokuroru" was inferior in the fungicidal effect to that of chloropicrin.Any controlling power of organo-mercuric fungicides was not expected in the practical use.