>> We have had a problem with a virulent strain of tobacco virus mosaic
> in commercial vegetable growing.A consultant(not trained in
> virology)has told us we need to control the viral vector, which is
> aphids. He postulates that the carrier of the virus is a native
> grass or weed in adjacent areas. He claims that we don't have to
> worry about the virus living in the fields we farm, because the
> virus will die when we plow the fields in the fall. Therefore crop
> rotation is irrelevant in viral control. Question: could the virus
> survive in dead or possibly slow decaying plants ? Thank you Rich
>>> I work on potato viruses so I am not an expert, but my first thoughts
on reading this was that you have been given bad advice. Crop rotation
is not irrelevant in virus control when controlling potato viruses and
I would guess that the same be true for any crop, though to differing
degrees. Perennial weeds can certainly act as reservoir hosts,
particularly where land remains uncultivated. I have looked up TMV at
a the following web site
"www.biology.anu.edu.au/groups/mes/vide/descr803", which you also may
find interesting to look at. It says that transmission is not by a
vector but by mechanical means and in the seed. So even annual weeds
could potentially be a problem. Good quality clean seed is obviously
essential.
One possibility is that your consultant is right about the aphid
vectors but wrong about the type of virus. He is correct that vector
control is important but I would still maintain that crop rotation and
weed control have a role. I would suggest that you get some more
advice from a different adviser who specialises in virology and is
closer to you than me and perhaps even get your virus properly
identified. We could do that here but I'm sure there are places nearer
to you.
I hope this has helped a little.
Regards
Dave
Dr D A C Jones
Virology
Scottish Crop Research Institute
Dundee
DD2 5DA
Tel (44) 1382 562731
Fax (44) 1382 562426
email djones at sari.scri.ac.uk
