Virus again

Alberto Castillo
Mon, 21 Apr 2003 20:00:26 PDT
Dear all:
              Thanks to German Roitman for taking the pictures and to Mary 
Sue for loading the images to the wiki.
              The five images are of the same plant, Hippeastrum 
teyucuarensis, and taken the same day. In the past and during trips with 
Patrick O’Farrell we found that plants of this species to be found in 
gardens were all virused, NOT showing symptoms except under stress (being 
dug, repotted, transplanted, etc.) This plant is of garden origin and the 
images evidently depict that the old leaves show clear symptoms of virus 
mosaic. In the new leaf the disease is masked and the surface is almost 
uniformly green. The mosaic shows itself at the emerging of the leaf, at the 
tips. As the leaf develops the pruinose surface hides the mosaic and the 
leaves look healthy. It can not be overemphasized the need of a quarantine 
period during which one maintains newly introduced plants away from the 
collection to see if they show signs of disease.
The case of the Clivia is the same, first it showed mosaic symptoms and then 
developed this condition that remains to be determined if it is micoplasm or 
leaf nematode attack. But, it shows clearly that an otherwise extremely 
robust and healthy plant as a Clivia is so weakened by the virus that it can 
develop a so far unknown condition.  What is so dangerous in a virused 
plant? It is a weakening disease affecting diversely different kinds of 
bulbs that has no readily available cure. In my opinion the worst part of it 
is that in the meatime the virused plant act as a carrier and every part of 
it, leaf, root, bulb or corm, pollen, flower, sap, has the ability to infect 
healthy plants through several mechanisms: sucking insects, tools, handling, 
leaves rubbing against each other, pollination, etc.
And Jennifer, you are right in that the image shows a plant with a curable 
fungic disease (Stagonospora curtisii) and an incurable virus one. 
Fortunately public campaigns on AIDS has taught us a lot about the way 
viruses behave and the contagion mechanisms. Hopefully this has raised 
awareness on the danger of this nightmare to our valuable bulb collections.
All the best and virus free conditions!

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