
True decline here is site-driven — standing water in stripped-topsoil lots, or concrete poured over the root plate — and shows as whole-branch flagging, where an entire limb browns at once rather than the crown thinning evenly. Interior needle browning and shed each fall is normal seasonal drop, and rust galls are cosmetic to the cedar itself; bagworm is the one that actually kills, because a branch stripped bare by bagworms will never refoliate.
It is native here and it plants itself — birds drop seed in fencerows, along drives, and in any corner that stopped getting mowed, so most red cedar quotes start with "this thing appeared and now it's 25 feet tall against the garage." The second driver is cedar-apple rust: red cedar is the alternate host, so anyone with apples or crabapples eventually wants the cedar gone.