Eventually, they can reach 1 inch in diameter and turn tan to black in color. The tiny black fruiting bodies of the pathogen are readily detected in the lesions on the upper leaf surface. Most lesions occur on leaf margins or in wounded areas. Control - Elimination of overhead watering and exposure to rainfall can reduce disease incidence and severity. Symptoms - Alternaria leaf spot is most commonly found on scheffleras, but is also known to occur on Polyscias spp.
Lesions are initially tiny translucent areas which later turn tan and have a chlorotic halo.
Sometimes a reddish-purple pigment is associated with leaf spot of variegated Polyscias balfouriana . Control - Alternaria leaf spot can be controlled with elimination of overhead irrigation and exposure to rainfall. In addition, use of greater than recommended levels of fertilizer result in reduced severity of Alternaria leaf spot on several other members of this plant family including schefflera, dwarf schefflera and false aralia. Symptoms - Pythium root rot of many foliage plants is most often caused by P. splendens . Plants appear stunted, chlorotic and wilted even when soil moisture is high.