interior shedding is normal ... can be increased due to various stresses like drought or winter ...

no conifer holds its needles forever ... its cyclical ...

hard to tell about yours.. without a pic ...

neighbor spent many years.. and many hundreds of dollars trying to spray 30 foot trees... they gave up.. as far as i know ... i cant conceptualize how a homeowner could do it ...

whatever it is.. it isnt a soil issue ... and they arent hungry.. so its not a food/fert issue ... besides.. if you fert your lawn.. they get what they need ...

thoug the picea pungens is a magnet for the needle cast ... it shouldnt be a problem with the dougs ... though i might be corrected on that ....

are we sure on the various IDs ...

need a pic ...

ken

The Douglas Fir NORTH of Lake Ontario have been increasingly affected by one of the Doug Fir needlecast fungi...mature trees being reduced to sparsely needled shadows of their former selves.

I'd be surprised if drought or winter damage was the culprit...the var. glauca is zone 3 hardy and does very well in the very dry interior valleys of the west (eg. yielding only to Ponderosa Pine in the Okanagan Valley).

be surprised if drought or winter damage was the culprit

==>> if i wasnt clear.. i meant in regard to normal interior needle shed ...

if OPs shed is beyond the usual interior shed.. then its disease ...

hence the request for a pic ... to see whats going on ...

ken