Question
Is it to early to prune mature blue spruce trees in Western New York ?

Answer
Whenever a situation calls for a conifer to be pruned or sheared, It is  typically recommended that one should avoid the period from early spring to summer to early fall. The following is a list of a few important reasons for this:

The unsympathetic heat of summer already stresses these trees to breaking point. Additional stress inflicted by pruning will not aid in its mission to survive.

This period during the growing season of trees is also the productive time when cankerous spores, such as Cytospora (the fungal agent which causes Cytospora Canker in Colorado, Norway, and White Spruces), is at peak production. By limiting the potential points of entry, the pathogen will have a less successful chance of infection.

Try to avoid early spring, for this is the time when trees are under a great amount of stress, for they are spending a huge amount of their stored energy reserves in order to produce flowers, fruit (cones), and new, juvenile leaves (needles). Pruning at this time will remove some of this stored energy and as a result cause further stresses.

Therefore,  typically prune in late fall.................often following the first frost