The disease is called angular leaf spot and managing the disease can be done but it will take some effort. The golden, orange spots on the leaves are caused by a fungus. Angular leaf spot is a common problem with these particular shrubs.
There are many varieties of Pittosporum and all of them appear to be susceptible. These shrubs range from small tree size (15 feet) to dwarf cultivars which only grow a few feet in height. Some of the plants are solid green while others come in a white and green variegation.
Once established, Pittosporum are highly drought tolerant and require little or no irrigation unless we go through a drought period. Actually, most of our woody ornamental shrubs require no irrigation once they are established. It is important for the leaves of the shrub to remain dry – so be sure to aim irrigation sprays toward the root area and not the leaves. Good air circulation is also important, so light, selective pruning can be done to allow for good air flow. Consider allowing these shrubs to reach their desired tree height if possible.
Chemical fungicides containing the active ingredients of myclobutanil or azoxystrobin can be applied to new growth. The old growth is already damaged and we cannot correct these evergreen leaves. It is also important to understand fungicides protect the new growth but seldom cure the disease. Please follow the directions on the pesticide label – the label is the law. Do not use a fungicide containing the active ingredient chlorothalonil (Daconil) as it has been known to damage Pittosporum.