Hello John,

Thank you for your question about your evergreen trees with yellowing and browning needles. Just as deciduous trees lose their leaves in the fall, evergreen trees also lose their old needles sometime in the late summer or fall.

Evergreens shed their older, interior needles as part of an annual growth cycle. Needles on the lower portions of the crown or closest to the trunk are most commonly shed, but trees stressed due to drought or root damage may shed more needles to keep the tree in balance with its root system. Soon-to-be-shed needles typically yellow first; then, they turn a reddish-orange or brown color before dropping off. Trees can have varying levels of needle shed, even within the same property or general area.
Source: Fading, Off-Color Pine Needles Normal in Autumn - Colorado State Forest Service (colostate.edu)

Conifers naturally shed needles in summer and fall | OSU Extension Service (oregonstate.edu)

If you are concerned about the health of your trees, I suggest you contact an ISA Certified Arborist to examine your trees. You can find one in your area by using this website: https://www.treesaregood.org/findanarborist/findanarborist

If you need additional information, I recommend you call the Deschutes County OSU Extension office in Redmond at<personal data hidden>. Ask to speak with Amy Jo Detweiler (oregonstate.edu), a member of the Horticulture Staff. Amy Jo welcomes your home garden questions and is a great resource.