Control of Root Rot and Wilt caused by Pythium myriotylum in Kangaroo Paw (Anigozanthos)

Abstract

Control of root rot and wilt on Kangaroo Paw (Anigozanthos) caused by Pythium myriotylum was tested, using artificial inoculations, in greenhouse experiments. Disease incidence in the inoculated but non-treated plots was 74% in Expt A (1999) and 46% in Expt B (2000). Disease incidence was significantly reduced by treatments with fenamidon (26 and 70%) and Terraclor SuperX (65 and 41%) in Expts A and B, respectively, in comparison with the non-treated plots. Disease incidence was reduced with Ridomil Gold by 7 and 48% in Expts A and B, respectively; with Dynone by 22 and 41% in Expts A and B, respectively; with Tachigaren by 20% in both experiments; and with Trichoderma harzianum treatment, disease incidence was reduced by 9% only in Expt B. Yields (recorded only in Expt B) obtained in plots inoculated with P. myriotylum were significantly lower than in the non-inoculated control plots. The most efficient treatment was fenamidon, with 324% more flowers than in the non-treated control. The number of flowers in terraclor SuperX, Ridomil Gold, Dynone and T. harzianum treatments was higher by 285, 249, 234 and 235% than in the non-treated control. In vitro tests demonstrated that the most effective doses, causing 50% inhibition of mycelial growth (ED50), were 0.09, 0.4, 0.4 and 4 μg/ml for the fungicides fenamidon, Ridomil Gold (mefenoxam), Terraclor SuperX (etridiazole + quintozene) and Dynone (prothiocarb), respectively.