Brian, I don't have any answers but I would ask a local nursery guy...not a big chain store guy. I hope you find an answer.
Tanya :)

Do you have any pictures?

If trees are Colorado blue spruce and inner needles on lower branches are dying first, while outer, new growth is green, the problem is most likely rhizosphaera needle cast. Cultural control includes increasing air flow by pruning lower infected branches and increasing tree vigor by watering, fertilizing and mulching properly. A fungicide (chlorothalonil, Daconil 2787) can be used as a preventive measure. Make first application at bud break, the second a week later, and a third three weeks later. For most trees, especially large ones, contact a professional tree care company to apply fungicide. (Dial U Brief: Rhizospaera Needle Cast, 1988.)

If the tree is a Colorado blue spruce, and outer and inner needles on lower branches are dying first, the problem is most likely cytospora canker. There may be resin or sap exuding out of the branch near cankered areas. Use same cultural control as above. No chemical control is available for cytospora canker. (Dial U Brief: Cytospora Canker of Spruce, 1989.)

Be sure to diagnose these diseases properly and do not mistake them for abiotic problems like winter injury. Note these two diseases occur on other species of spruce, but are most common on older Colorado blue spruce.

Rhizosphaera Needle Cast

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