He is to burn the fabric, weave, or knit, whether the contaminated item is wool or linen or leather. Since the mildew is harmful, the article must be burned up.
Jewish Publication Society of America Version (JPS1917) - Leviticus 13:52 >And he shall burn the garment, or the warp, or the woof, whether it be of wool or of linen, or any thing of skin, wherein the plague is; for it is a malignant leprosy; it shall be burnt in the fire.