Evaluation of fungicides for the control of downy mildew (Peronospora parasitica) in canola

Downy mildew, caused by Peronospora parasitica Pers. ex Fr., is an important disease of canola that has implications during early seedling establishment. The fungus invades young seedlings and severe infection results in premature defoliation. In worst cases, the systemic infection may even kill the seedlings. Current commercial varieties of canola are very susceptible to downy mildew. Therefore, efficacy of various fungicides was tested for the control of downy in a growth chamber. Four fungicides, Jockey® (a.i. 167 g/L fluquinconazole), Aliette (a.i. 800 g/kg fosetyl), Coppox (a.i. 500g/kg copper oxychloride) and Benlate (a.i. 500 g/kg benomyl) were evaluated as seed dressings, each at 2 g a.i./kg seed. In an another experiment, Axiom MZ 720 (a.i. 640 g/kg mancozeb, 80 g/kg metalaxyl) was tested either as a seed dressing at 2 g a.i./kg or as a combination of seed dressing and foliar spray applied at 5, 7 and 15 days after inoculation or one day before inoculation. None of the fungicides except Jockey® tested in the first experiment were effective as a seed dressing to provide protection against downy mildew. However, Axiom MZ 720 as a seed dressing provided protection for only one week. The foliar spray of Axiom MZ 720 was not effective in providing protection if sprayed after inoculation. However, when it was applied as a foliar spray a day before the inoculation, it provided excellent control of downy mildew by completely inhibiting the disease development. Therefore, the control of downy mildew by foliar application of Axiom MZ 720 before the onset of the infection seems promising under growth chamber conditions and needs to be further tested under field conditions.