Infection will occur if the weather is cool and rainy during leaf emergence. The initial flush of leaves during extended periods of dry weather and above normal spring temperature are the only ones subject to infection by this organism. A copper fungicide just prior to bud opening is effective. This disease is most severe on members of the red oak group but white oaks are also infected. The disease is most severe in late summer and early fall.
Severe defoliation can occur.
Actinopelte leafspot is a primary leafspot but can be found associated with other fungi. Infected leaves should be destroyed and trees which are severely defoliated by the fungus should be fertilized slightly more than normal to stimulate growth. Check foliage for possible minor element deficiency. Damage is sometimes associated with low levels of iron. Infection by this fungus can cause small spots on the foliage of red oaks.