Lilies forum: Fall clean up - Virus transferal risks?

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Skåne, Sweden (Zone 7b)
Bulbs Lilies Bee Lover Irises Celebrating Gardening: 2015
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William
Nov 10, 2015 2:59 PM CST
I'm aware that dead debris can still be virused, however I wonder at what point it's safe to cut lily stems without risking virus transferral to the bulbs?

I'm assuming if the stem is completely dead as in browned, feeling dry and hollow it would be okay, but what if it's just completely brown but the stem feels as it still has some moisture in it?

Ideally I'd prefer to wait until the stems were very dry to cut them or simply tear them out if possible as I'm not concerned with a bit of untidiness at this time of year, but this causes the leaves to spread around and as they easily become Botrytis infected in my climate during late autumn this causes extra problems when they need to be collected and discarded. At this point I try to disinfect my pruners or clean them between cultivars, but perhaps that is unnecessary?



[Last edited by William - Nov 10, 2015 3:00 PM (+)]
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Name: Lorn (Roosterlorn)
S.E Wisconsin (Zone 5b)
Lilies Seed Starter Pollen collector Bee Lover Region: Wisconsin
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Roosterlorn
Nov 10, 2015 8:02 PM CST
The risk is most likely very low since the plant is in a 'dying down' mode coupled with ever decreasing cold temperatures. A virus doesn't act like a flash fire; rather, it moves slowly over time throughout the plant. If the cut is made at 7 or 8 cm, about 3 inches, chances are the stem would be completely dead before a virus ever made it to ground level. I'm making the assumption that a virus dies as soon as the host dies.

As far as botrytis in the late fall, that's quite natural and usually harmless because it is so late. Botrytis is ever present anyway, being a natural part of the eco system cycle. A typical general fall clean up should be all that's required without much fuss. In the early spring, I spray the entire garden surface with Bonide copper fungicide just around the time the noses start popping up and water it in, or apply it just before a predicted rain.

For the record, I usually make 3 passes each fall removing fallen stems, etc., the last pass being around Christmas time. If a stem is still tight at that point it stays in until spring. After all tree leaves have fallen, I use a gas powered leaf blower to blow all the unwanted stuff out, including the old summer mulch. That all gets burned. Smiling
Name: Rick R.
near Minneapolis, MN zone 4a
I was one of the first 300 contributors to the plant database! Garden Sages The WITWIT Badge Garden Photography Region: Minnesota Plant Identifier
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Leftwood
Nov 10, 2015 9:24 PM CST
I'm not sure anyone actually knows the real answer of how long it take for a virus (assuming all viruses are the same) to die, as it would require some in depth lab work. I don't fret too much about possible virus spread that I can't really control. My next door neighbor has a bed of 50 Lilium lancifolium that are sure virus carriers, but it doesn't seem to cause much problem. On the other hand, I do have several pairs of pruners so I can minimize possible virus spread when cutting different live stems, as cut flowers, for instance. This way I don't need to bother with disinfecting the pruners. (Also, I am constantly misplacing them, so I need multiple pairs. nodding )

Rather than tearing the dead stems, you might consider pulling them instead. I don't get dead leaves flying off anywhere. There are advantages and disadvantages to this method, and I don't really advocate pulling over cutting (or vice versa), except perhaps in specific cases. There is a bit of a learning curve the the process, the object being to quickly snap the stem from the bulb in one yank, but not necessarily pulling the stem out of the ground with that initial jerk.
Skåne, Sweden (Zone 7b)
Bulbs Lilies Bee Lover Irises Celebrating Gardening: 2015
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William
Nov 11, 2015 2:45 AM CST
Thank You! Lorn and Rick. As always, most valuable advise!

Lorn, it makes sense to cut a bit higher up the stem and I'll do so in the future. Yes, not to concerned about Botrytis in the autumn and your advise about spraying in the spring is for sure a good one. Copper fungicides are however no longer sold to the home gardener here. I could get ingredients to do my own Bordeaux Mixture, but I'll probably try some preventive spraying with baking soda and soap weekly instead as I seemed to have some success with it this year, even though I started very late in the season (after symptoms were visible) and only continued until bloom.

Rick, I have a couple of pruners already, but getting a few more seems to be a very good idea! I believe for instance Tobacco mosaic Virus is supposed to survive up to 50 years in dried leaves, but I assume it would last much shorter in the garden and of course most viruses would go inactive long before that.

Going back I see I was very unclear in my writing *Blush* . I didn't mean to say that the actual removing of stems caused the leaves to spread around much, but rather that waiting too long made them fall of by themself and that in turn made them spread in the wind all over the place, thus risking eventually ending up in my compost.

I have no problem pulling the stems from the Asiatics, but not sure I could manage that with the OT lilies, not before winter/spring when they are more decayed anyway.

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