virus in hippeastrum
Sat, 18 Nov 2006 20:17:07 PST
Anne, Robert ~

Virus in amaryllids is an insidious thing.  Since these plants are asexually 
propagated, sooner or later, they will contract one, or more, of the viruses 
to which they are prone.  In the case of Dutch-raised Hippeastrum, they are 
grown in warm greenhouses where the bloom stems are harvested for the cut flower 
trade and the bulbs subsequently dug and sold into the dry bulb trade.  
Viruses are spread from bulb to bulb when the bloom stems are cut with the same 
knife (or some other instrument) unsterilized between cuts; the classic method by 
which a virus moves from the host plant to infect other plants.  Having grown 
various hippeastrum for some fifty years, it is just something that one 
accepts -- if you want those brilliant blooms to brighten the dull days of winter!  
Given the loose, humusy soil these bulbs revel in, warmth, moderate fertilizer 
(highest in potash), good light and adequate water, they will produce each 
season a bulb large enough to throw at least two and often three bloom stems.  
'Red Lion' and 'Appleblossom' are two that do well in spite of their viral load.

Many amaryllids are multiplied by what is known as "cutting" or "parting."  A 
bulb is cut into sections that resemble the sections of an orange, incubated 
to develop the latent growth points and potted up.  It is essential for virus 
control to use aseptic conditions, something I feel fairly certain is not 
common practice, with the predictable result of rapid spread of virus to the 
entire stock.

The advice to discard virus-infected bulbs is probably good advice -- 
depending on what else you grow.  If you discard the bulbs, you will find the 
replacement bulbs to be no better.  So, it's just something to live with and be very 
careful when cutting the plants for any reason to not use that knife again on 
something else without sterilizing it (immersed overnight in 70% ethanol). 

If you want virus-free hippeastrum, you will need to make your own crosses 
and raise the seed to maturity.  You will find the seedlings to be robust 
growers, multiplying and blooming much better than the virus-infected parents.  The 
rub to this process, alas, is that you won't often find a seedling that is 
better in all respects than either parent!

Dave Karnstedt
Silverton, OR 
Mediterranean climate -- cool, wet winters, hot, dry summers.  Zone 7

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