Sclerotia are structural features produced by certain fungi and are not classified as either symptoms or signs of a disease. In the context of plant pathology, "signs" refer to visible evidence of a pathogen, such as the actual pathogens themselves (like fungi or bacteria), while "symptoms" refer to the plant's response to the disease (like wilting, discoloration, or necrosis).
Sclerotia are hardened masses of mycelium that can survive unfavorable conditions and can be a form of fungal survival rather than a direct indicator of a plant's health alteration. Therefore, they are considered a sign of the presence of certain fungal pathogens, such as those in the genus Sclerotinia or Botrytis.