25-Jun-09 08:19 | Eric Stafne

Not all things that look like disease are disease.  Take Bunch Stem Necrosis for example.  This is a physiological disorder caused by abiotic factors.  Improper balance between Calcium and Potassium or Nitrogen deficiency can cause these symptoms.  Poor environmental conditions during time of pollination and fruit set can also contribute.  Phil Salingue brought this to may attention as he has had problems with this on his Chambourcin.  The best thing to do is a petiole analysis to understand what is going on in the vine nutritionally.  Of course, the weather could have played a major role with lack of pollination due to rainy, cool conditions.  For direction on how to do a petiole analysis go here: http://www.grapes.okstate.edu/PDFs/petioleanalysis.pdf

I will also post a photo of Bunch Stem Necrosis here when I get a chance: http://www.grapes.okstate.edu/grape_pests.html