Need pictures for correct diagnosis. It sounds like the natural tomentum that naturally occurs on Foxtail Palm petioles. It is a dark fuzzy speckling.
Tomentum may refer to the following:
• In botany, a covering of closely matted or fine hairs on plant leaves. (see Trichome#Plant trichomes)
(reference: ENH1077/EP344: Normal "Abnormalities" in Palms )
In some palms ( e.g., Wodyetia bifurcata, Veitchia spp.) black-colored scurf appears at the bases of the petioles (Fig. 10). This black scurf is very similar in appearance to the sooty mold often associated with palm aphids, scales, or mealybugs. In other palms, new spear leaves and young petioles are covered with a thick pinkish to brown fuzzy scurf that is easily rubbed off. The light salmon-colored scurf on new growth of Latania palms (Fig. 11) is useful in distinguishing this species from the similar Bismarck palm (Bismarckia nobilis), which has very little scurf.