Peronospora farinosa - downy mildew

 I left the spinach in the greenhouse for a few weeks after discovering downy mildew to watch what would happen.  I was not disappointed.  Besides turning fuzzy, the spinach leaves turned yellow and eventually shriveled up and died.

http://mtvernon.wsu.edu/path_team/DiseaseGallery/spinach-downy-mildew-4.htm

The above picture shows downy mildew sporangia, which I think must be what I called the 'fuzzy' grey stuff on the spinach leaves.  The sporangia is where the spores are formed.

The fungus 'ate' through these leaves! Gross!

What is the plan of attack for next semester?  Not growing spinach is not an option.

1. Leave the greenhouses spinach free for at least two weeks.  Downy mildew is specific to spinach.  Without a host it should die.
2. Sanitize the flats I use to grow greens in.  At the end of the season they are pretty dirty and the plant residues on them could harbor spores.
3. Use a spinach variety that is resistant to more strains of downy mildew.  Since it is such a widespread problem, new varieties of spinach are bred to be more resistant.  Space, the variety I have been using, is resistant to strains 1-3.  In the spring I'll use a variety that is resistant to at least strains 1-7.