April 10, 2013

Colletotrichum: another spinach disease

I've been sick this week, and so is the spinach.   This new spinach disease is Colletotrichum (aka anthracnose).

Symptoms include: tan-brown circular lesions that coalesce  resulting in severe blighting of foliage.  Lesions can also be water-soaked, as in the below, righthand picture. Eventually diseased tissues are covered in small black fruiting bodies (the 'mushroom' part of the fungus).

Colletotrichum is seed borne, so using disease-free seeds is the best way to avoid it. I've heard washing seeds in hot water will kill this kind of disease, but I think you need a special seed-dishwasher.  (Does anyone know about seed washing?)

This is the second really gross disease spinach has had.  (Remember the downy mildew problem last fall?)  This leads me to a very bold idea:

Maybe spinach is not a good crop for bench-top winter growing.

Here's why:
  • Spinach is susceptible to many diseases when grown in greenhouses.  
  • Spinach is slow growing.  It has a slow turnover time.
  • Spinach takes a long time to harvest.
  • Spinach can have low yields per square meter. 

Note that I'm being specific to bench-top growing, and also that I said maybe.  There are big differences between bench-top growing in trays (what I'm doing) and in-ground growing (what farmers/gardeners do).

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