Home and Building, Volume 18 Number 1 (June 1955)
Leaf Scurf: This is characterised by raised, corky outgrowths generally on the under surface of the leaves. The corky spots may occur in small groups or cover large areas, and usually appear irregularly rather than in a particular pattern.
Research has not been able to determine the exact cause of this scurf, but has determined that it is probably due to a physiological disturbance brought about by improper growing conditions rather than by a parasitic disease. There are, however, other types of scabby lesions occurring in the South which are caused by fungus.page 80