Bunching disease is caused by a mycoplasm-like organism, but it spreads from tree to tree probably by vector insects. Bunching is another term for "witches broom" or "brooming."  We do not have a lot of information about this disease.  Our sources recommend removing an infected tree or pruning out affected parts well below the symptoms, in order to prevent spread to other trees. Destroy infected parts. 

ECN

Are there growing conditions that encourage this infestation?  Are there any suggestions to prevent continued infestation and loss of the entire nut grove?

Nut trees in general are not well adapted here. They may grow but may not produce nuts reliably.  We do not have the information and research that you are looking for.
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