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Saturday - January 29, 2011

From: Palm Beach Gardens, FL
Region: Southeast
Topic: Non-Natives
Title: Black fungus on non-native ixora from Palm Beach Gardens FL
Answered by: Barbara Medford

QUESTION:

We have 7-8 ixora plants that are side by side and all have developed a black fungus or substance on them. The substance is not only on the plant, but has spread to the wall they are adjacent to. Can these plants be salvaged?

ANSWER:

Ixora coccinea is native to tropical Southeast Asia, including India and Sri Lanka, and is therefore out of our range of expertise. The Lady Bird Johnson Wildflower Center is dedicated to the growth, propagation and protection of plants native not only to North America but to the area in which those plants are being grown. This Floridata article will give you more information, but does not mention a disease such as you have described.

This sounds like a sooty mold, which can often be caused by mold growing on the honeydew exuded by aphids. However, we are not sure if that mold would spread to a wall. This article Floridaplants.com has information on pests and diseases of Ixora coccinea. Of special interest in your situation is this excerpt:

"Insects and Diseases - This plant is subject to nematodes and should be mulched heavily. It is also attacked by aphids, mites and scale, which cause sooty mold."