I work with pathologists. It's a dark and gloomy plant world through their ocular perspective of plant imports. The un-calculable probability of cross infection and potential damage to monoculture from one disease crossover is too grave of a risk. Thus the movement to exclude and prohibit plant imports until a pest risk assessment has been completed. William Aley Silver Spring, MD Sent from my iPhone > On Apr 7, 2014, at 3:06 PM, Rodger Whitlock <totototo@telus.net> wrote: > >> On 7 Apr 2014, at 8:59, Jerald Lehmann wrote: >> >> I'm trying to figure out what is so bad about growing virused plants. > > The issue (or so it seems to me) isn't that virus X slightly weakens plant Y; > it's that the same virus will kill plant Z. > > A further point: any plant propagated vegetatively will gradually become > infected by more and more viruses. Each virus does little, but in aggregate > they weaken a plant making it progressively less easy to grow and propagate. > The cleaner the growing conditions, the more slowly this process takes place. > > This is probably the reason that many (most?) old cultivars of various garden > plants are out of cultivation. Or take Cosmos atrosanguineus for example: forty > years ago Graham Stuart Thomas considered it miffy and difficult, and it was > effectively unobtainable. Then someone must have run it through tissue culture > and gotten rid of the accumulated viruses, and these days it's widely available > and easily grown. > > To put this in other words: you may think virus infections are innocuous, but > they aren't. > > > -- > Rodger Whitlock > Victoria, British Columbia, Canada > Z. 7-8, cool Mediterranean climate > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://pacificbulbsociety.org/list.php > http://pacificbulbsociety.org/pbswiki/