Tag Archives: pathogens

Downy mildew of brassica vegetables

Downy mildew of brassicas (Hyaloperonospora parasitica syn. Peronospora parasitica) is a fungal-like oomycete that can be devastating in cooler, wet weather. While the ideal temperature for downy mildew development is 8-16˚C it can infect in temperatures outside that range. Prolonged leaf wetness due to fog, dew, or evening irrigation can create ideal conditions for the pathogen to develop.

Downy mildew is most devastating on Continue reading Downy mildew of brassica vegetables

Stemphylium is the new Botrytis

Stemphylium leaf blight (Stemphylium vesicarium) of onion starts as yellow-tan, water-soaked lesions developing into elongated spots. As these spots cover the entire leaves, onions prematurely defoliate thereby reducing the yield and causing the crop to be more susceptible to other pathogens. Stemphylium was first identified in Ontario in 2008 and has since spread throughout the Holland Marsh and other onion growing areas in southwestern Ontario.

Stemphylium leaf blight can sometimes be misdiagnosed as Continue reading Stemphylium is the new Botrytis


Margaret Appleby, IPM Specialist

OMAFRA, Brighton

Biofumigation is defined as suppression of soil-borne pests and pathogens by the use of plants that contain inhibitory chemicals. The plants can be harvested as rotation crops or ploughed back into the soil as green manure. The fumigate properties of these crops have been known for a long time, recently has had a closer look due to the phase-out of the methyl bromide and other fumigants under the international Montreal Protocol. Advances in biopesticides with fumigant properties and application technology make this an economical possibility for commercial agriculture.

Continue reading Biofumigation