Virus in Nerine. Was: Nerine sarniensis

John Lonsdale
Mon, 07 Nov 2005 09:29:31 PST
There are two different aspects to this topic.  One 
relates to the use of high nitrogen fertilizers resulting 
in larger softer plants that are more susceptible to aphid 
attack, with subsequent transfer of virus.  The other 
relates to activation of latent virus or the appearance of 
symptoms in otherwise asymptomatic infected plants. 
 Plants are riddled with all sorts of viruses that don't 
cause symptoms when the plants are grown optimally, and 
the viral load can be large without any indication of 
infection.  Plants become symptomatic when stressed.  I 
brought robust totally asymptomatic petiolarid primulas 
from Scotland to the SE of England and within days of 
experiencing heat stress they became distorted and 
streaked.  It doesn't matter whether the plants are 
greenhouse grown or field-gown, the principles are the 
same.  I doubt there is such a thing as an unvirused 
plant, it is just a question whether the infection is 
sufficiently active or the plant sufficiently stressed for 
the symptoms to appear.


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