What is the Cause of Black Sooty Fungus on Plants in Southwest Florida?
Black sooty fungus is a relatively common problem on citrus, magnolia and hibiscus trees, rhododendrons, bamboo, crape myrtle, and other plants in the state of Florida. The unsightly mold is caused by several insects and blocks sunlight from the plant if treatment is not applied. Although the fungus affects a wide variety of plants, the detection method and treatment plan is basically the same. Does this Spark an idea?
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Causes
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Black sooty fungus on plants is the result of an infestation of several insects such as soft scales, tree hoppers, aphids or other honeydew-excreting insects. The Florida climate is humid, and black, sooty mold or fungus forms on the honeydew the insect has excreted. During the rainy seasons, the rain cleans away the sooty mold, but during the dry periods, it can build on the tree. Sooty fungus is generally harmless to people, but shades leaves on plants, preventing photosynthesis. This eventually could slow down the growth of a plant if left untreated.
Identification
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Examine the leaves of the plant that you suspect has the sooty fungus. Black sooty fungus can affect many plants, trees and even vegetable crops in Southern Florida, so it is best to diagnose it first if you believe your plant has a problem. Look for a black powdery substance on the leaves, especially the underside, because that is where many of the insects that excrete honeydew prefer to hide.
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Pruning
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Snip off any leaves or branches that are heavily infested by insects with pruning shears. Prune the branches back to the parent branch with the shears. Make a clean cut and leave as little stub as you possibly can.
Treatment
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Spray your plant with horticultural oil and evenly cover all the leaves, but do not let it drip off the plant or tree. This will rid the plant of all of the insects and the black soot will dry out. The best way to treat black fungus is to get rid of the insect problem first.
Prevention/Solution
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Apply the oil spray in early spring to control the population of insects before they grow into their adult stage. Many insects are in their nymph stage early in the season, and by late summer it will be more difficult to get rid of them with the oil spray, since their adult waxy covering will help protect them.
Wash away the black sooty fungus with a garden hose as soon as you see it. The oil spray will be the solution to preventing the fungus from returning in the long term.
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