Termite evidence
Look for workings, insects or soil-like material associated with internal galleries.
Two processes can share one piece of timber
Termite damage versus wood rot
Termite damage and fungal timber decay can occur separately or together. Both can weaken timber, but their causes and required responses differ.
Decay evidence
Persistent moisture, softening and fungal change require the water source and timber condition to be addressed.
Both together
Do not assume treating insects repairs decay or that drying timber resolves pest activity.
Repair decision
Structural adequacy belongs with a suitably qualified building professional.