Regular maintenance of your hand-knotted rug such as vacuuming, rotating and periodic inspections for moths activity, will keep moths from settling in your fine rug.
Do not store unprotected rugs for a long period of time, as moths like to settle in dark quite areas, especially in the back of your fine rug.
Cases of Mildew happen when a rug is left wet for too long. The best way to eliminate and prevent mildew from spreading is to have your fine rug professionally washed, cleaned and thoroughly dry.
When in doubt call the Professionals.