Actinopelte Leafspot (fungus – Actinopelte dryina): This disease is most severe on members of the red oak group but white oaks are also infected. The spots are small (2 to 5 mm in diameter), round and reddish-brown in color. 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. Newly planted trees (first 3 years) are more subject to attack by this disease than well established trees.