Bulb Virus Horror/Mystery

[Alan_b]

On 31st January I found a small clump of woronowii that showed the symptoms of a virus, lighter-coloured streaks on the leaves.  I took a photo:



This was disappointing but the snowdrops were not precious so I did not feel too bad about digging-up the clump and disposing of it.  In the past I have found and removed the odd virused bulb and last year I had one pot of quite a precious snowdrop where all the bulbs (10 or so) were heavily virused despite having no notable symptoms the previous year.

Now skip forward to 4th March, the snow had cleared, it was reasonably warm and I was able to get back into the garden.  I found another small clump of woronowii showing similar symptoms.



Perhaps the marks are not quite as obvious as in the first instance but these are right by the path and I am sure (99%) that there were no visible symptoms on 31st January when I found the first affected clump.  Worse still I went on to find a whole area nearby, an overcrowded drift of plicatus covering about 2 sq. metres in area, where all the bulbs were similarly virused.  So I spent an unhappy afternoon digging them up.  I cannot guarantee that I looked closely at these in January but surely I would have noticed (the affected clump I found was nearby)?

So the horror is that suddenly I seem to have quite a major problem.  Hopefully I caught it in time this year and it will not spread and hopefully the bulbs I have in pots, which is most of them, have been spared.  But what is the incubation period for a bulb virus like this.  Am I observing bulbs that were infected last year (or earlier)?  What causes the symptoms to manifest, or not?  Could our recent spell of very cold weather and snow have made the symptoms more obvious?  Could some bulbs be "carriers" and have the virus without manifesting symptoms?  Is the virus spread above or below ground?  Why is it almost always the entire clump that is affected rather than random bulbs?

Hopefully there will be some knowledgeable people here who can help me answer some of these questions.   

[Brian Ellis]

I understood that slugs, snails and insects can transfer it, hence I disposed of a whole (large) clump of G.'Priscilla Bacon' earlier this year. 

[Alan_b]

Yes, you mentioned that to me when I spoke to you in person earlier this year, Brian.  But don't you find it odd that the entire clump was affected (as I think you said) rather than random bulbs amongst it?  Whatever the method/insect of transmission, it seems to be very comprehensive.

[David Nicholson]

You got a sideline as a headline writer for the Daily Express by any chance Alan?

[Alan_b]

No, David, but I do urgently need to get on top of this problem so I was trying to attract the attention of the well-informed experts here in the hope of getting advice.

[David Nicholson]

I think I would have been tempted to pot them up and park them in some part of the garden where I didn't have any Snowdrops and see what they look like next year. It could have possibly been weather damage to blame couldn't it?

[Alan_b]

I'm pretty certain the problem is not weather damage, although I could believe that the effect of the weather has been to make the symptoms more visible.  So far the problem has been almost completely confined to bulbs that are "ordinary" and which I have in plenty so it's safer to dispose of them.  Potting them up would take a lot of time and I only have a small garden with few options for "safe" areas to leave the pots.   

[ArdfearnAli]

Hello,
        I have found a very similar streaked effect not on snowdrops but lilium and also colchicum from time to time. I first thought it was a virus but a few I forgot to remove seemed to grow out of it the following year. I put it down to a either a nutritional problem or climactic effect.
It could also be caused by selective weed killer damage if its been used near by. There are a few weed killers that can remain in soil or can be introduced from either green waste (ie grass cuttings etc) used to make compost. It can also be present in manure when livestock have eaten sprayed foliage around farms. Two that jump to mind are Clopyralid and Triclopyr which are present in a lot of selective lawn weedkillers and also selelctive agricultural herbicides. They can be introduced as said through contaminated compost or manure and can remain residual for 1 to 2 years. They effect is very similar to virus and even in very small concentrations are also capable of killing young seedlings.

Hope it turns out to be the weather. It seems odd that such large numbers have been infected so quickly.

Alasdair

[tonyg]

I too have noticed something like this on colchicum leaves since the snow cleared.  I'm sure I would have noticed it before had it been there.  Maybe ArdfearnAli is correct in thinking it's a climatic/nutritional issue although these factors could just be revealing a pre-existing virus problem.  I'm not doing anything in a hurry but will mark and move the effected bulbs (onto my allotment, out of the garden) - see if they retain the problem next season.