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!
Alberto
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