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Onion and shallot woes

• Message 1. 

  Posted by Holbert (U3994703) on Wednesday, 20th July 2011

  I went to lift my shallots today as the stems are dying back.
  
  However, on closer inspection, I realised the stems aren't the onion brown I was expecting, but are going black and when I touch these wizened stems, clouds of black powder comes off into the air.
  
  Obviously it would seem to be a mould of some sort but what is it and what shall I do about it? I've googled 'onion black powder' and a common suggestion seems to be a black mould called Aspergillus niger. BUT all the articles I've found suggest this mould affects crops post harvest in storage, not pre harvest.
  
  I've noticed my onions are similarly affected and almost half of them have produced flowers. So it's a bad crop of alliums for me this year with hardly any being able to be stored by the looks of it!
  
  But what shall I do about this black mould? Don face mask to avoid inhaling it and lift the shallots and cut the black wizened stems off? Has anyone had anything similar please?

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• Message 2

  , in reply to message 1.

  Posted by Holbert (U3994703) on Wednesday, 20th July 2011

  Here are a couple of photos :
  
  [IMG]/IMG]
  
  [IMG]/IMG]
  

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• Message 3

  , in reply to message 2.

  Posted by Holbert (U3994703) on Wednesday, 20th July 2011

  Sorry, the above photo links don't work, I don't know why. I've obviously been away so long I've forgotten how to post photos.

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• Message 4

  , in reply to message 3.

  Posted by Holbert (U3994703) on Wednesday, 20th July 2011

  Now these ones do work, hurrah:
  
  
  
  
  

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• Message 5

  , in reply to message 4.

  Posted by Papa Nopsis (U14479902) on Wednesday, 20th July 2011

  
  
  Interesting! But I wonder how you will eradicate the infection from the soil, unless by rotating the crops more and adding manure and compost?
  
  It looks as though the onions are a write-off.
  
  Does the dust get right inside the onion skins?

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• Message 6

  , in reply to message 1.

  Posted by 7magpies (U8108459) on Thursday, 21st July 2011

  My shallots look like that this year. I wouldn't say there were clousd of black poder in my case, just a slight sootiniess. I'm putting it down to the strange weather - a hot,dry spring followed by a lot of dampness.
  
  I'm finding that most of them are OK if I trim them and rub off the outer layers, but many still seem to have thick necks, so I'm afraid they won't keep well. Whatever is affecting them seems to have made them die back too early, or something.
  
  Today is bright and dry so I am about to spread them all out on a tarpaulin in the sun to dry off, then haul them under cover tonight before the next rain comes.
  
  I am not sure whether the blackness is something really nasty that shouldn't be composted, or whether it's just some opportunitic mouldiness that has crept onto stressed plants. I usually reckon that since compost relies on fungi and bacteria to break down, putting stuff like this in the compost heap won't hurt.
  Or am I wrong?

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• Message 7

  , in reply to message 6.

  Posted by 7magpies (U8108459) on Thursday, 21st July 2011

  "Clousd of black poder" - did I really write that?
  Clouds of black powder. That's more like it.

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• Message 8

  , in reply to message 6.

  Posted by Italophile (U12516505) on Thursday, 21st July 2011

  
  I am not sure whether the blackness is something really nasty that shouldn't be composted, or whether it's just some opportunitic mouldiness that has crept onto stressed plants. I usually reckon that since compost relies on fungi and bacteria to break down, putting stuff like this in the compost heap won't hurt.
  Or am I wrong? 
  
  It really depends what the black stuff is. If it's harmless fungal, it won't hurt the compost. Nasty fungal is another matter. It will live on. Unless someone comes up with an answer either way, I wouldn't risk it.

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• Message 9

  , in reply to message 7.

  Posted by Holbert (U3994703) on Thursday, 21st July 2011

  Thanks 7magpies. I think I'm just going to have to do as you are and dig 'em up, try to dry 'em out and see what happens.
  
  *sigh* So annoying that my lovely bulbs are not going to keep by the looks of it. A lot of them have brown slimy patches on, no sign of white rot though, so they are definitely going to be no good it would seem.

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• Message 10

  , in reply to message 9.

  Posted by Papa Nopsis (U14479902) on Thursday, 21st July 2011

  Aspergillus can be a nasty poison, so don't eat the mildew!
  
  I planted shallots setts after broadbeans were finished in mid- june, and now the shallots are doing well; had a bunch for lunch. Everybody's plot is different

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• Message 11

  , in reply to message 10.

  Posted by farmerSteve (U2644680) on Friday, 22nd July 2011

  The disease of onions is powdery mildew.
  provided the bulbs are dried off properly it should not harm them unless the disease has gone right down the stem
  
  A big danger from any mould is inhaling the spores which will give "farmers lung" which is similar to emphysemia very nasty
  if there is any risk I would wear a mask

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• Message 12

  , in reply to message 11.

  Posted by Papa Nopsis (U14479902) on Friday, 22nd July 2011

  Sorry about that Holbert! Perhaps to think about the soil just there and try again, or try something else in the rotation of things.

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