Symptoms - Xanthomonas leaf spot of Aralia has become more common during the past five years. Lesions are initially tiny, corky appearing areas which are seen on the lower leaf surface and can be easily mistaken for edema or phytotoxicity. Control - See those listed for Alternaria leaf spot with respect to irrigation methods and host nutrition. 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.