By Kori ~ November 23rd, 2010.
This weekâ€™s Wine Word of the Week is leafroll virus.
Official definition from Jancis Robinsonâ€™s The Oxford Companion to Wine:
Leafroll virus is a virus disease that is widespread in all countries where grapes are grown. The disease is now thought to be due to a complex of different viruses which can be differentiated. Of all the virus diseases of vines, it can have the most serious effects on wine quality. These dramatic effects are not understood by the many appreciative tourists in wine regions who marvel at the attractive autumnal colours of vineyards. Few realize that these colours often indicate the presence of a serious disease, although other factors may contribute to autumnal colours. Leafroll virus causes yield to be reduced by as much as 50 per cent. Wine quality is also affected because of delayed ripening. Thus wines from infected vines are lower in alcohol, colour, flavour, and body. The disease does not kill vines, so they are infrequently removed. Yet removal is the only known treatment to overcome the effects of the virus.
Laymanâ€™s terms from Kori:
Leafroll virus can be responsible for the lovely gold and red vine leaves in the vineyard in autumn. This color display, coupled with a downward rolling of the leaf blade, is an indication of delayed crop ripening and reduced yields.
Filed under: Wine Word of the Week