Mexican Orange Shrub Diseases

The Mexican orange shrub is a fast-growing flowering plant that reaches 8 feet in height. Its name comes from its white flowers, which release a sweet fragrance similar to that of orange blossoms. They bloom in late winter or early spring, attracting bees to your garden. This plant is susceptible to few diseases, most of which you can control by keeping it properly nourished and irrigated.

According to an entry in the 2001 edition of "Sunset Western Garden Book," the Mexican orange shrub often develops root rot or crown rot if it is planted in poorly drained soil. Root and crown rot are fungal diseases that affect the roots of ornamental shrubs, making them soft and brown, and unable to support their plants. The symptoms of these two diseases include wilting, thin and yellowing foliage, and slow growth.

A low level of iron in plant tissue causes chlorosis in Mexican orange shrubs. Plants use iron to produce chlorophyll, the substance that turns leaves green. But more importantly, chlorophyll makes it possible for vegetation to transform sunlight into food. The first symptom of chlorosis is the yellowing of foliage. As the iron deficiency becomes more severe and the disease progresses, the leaves lose all of their green color and develop brown spots. Without iron supplementation, a Mexican orange shrub suffering from chlorosis eventually dies.

A darkening of the tips and margins of leaves characterizes leaf necrosis, a disease that occurs when water can’t reach the foliage on your Mexican orange shrub. Dry and hot conditions, over-fertilization, or roots incapacitated by root rot, cankers and chemical contamination all have the potential to cause leaf necrosis.