Walla Walla, a well-known wine region in Washington State, was believed to be exempt from the vine louse (phylloxera vastatrix). Therefore, the recent discovery of the louse that is so dangerous to the vines dealt a heavy a blow to the wine producers. All of Washington, and especially Walla Walla, has the kind of sandy soil that the vine louse does not like. Therefore, according to the Washington State Wine Commission, a very large portion of the vineyards are not grafted on resistant American rootstocks.
Apparently, some vineyards in Walla Walla have been weakening for several years but no one thought it was due to phylloxera. Now, however, the louse has been identified as the culprit and action can be taken. However, weakened vines can produce good quality and although the solution, in the end, is to graft, the producers can do their replanting at a slow pace.
Read more about the phylloxera in Washington State: winespectator
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