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What is Sooty Mold?

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Sooty mold
Photo Credit: ©Buglady Consulting
As its name implies, sooty mold is easy to identify by its “sooty” appearance as seen on this palm tree.
“How did my plants get so dirty?”

The real question is, are you looking at dust, dirt and grime, or are your plants showing signs of fungal growth? No matter where you live or what kind of plant you have, sooty mold may be the cause of unsightly black residue on the plants in your home or landscape.

Sooty mold is a dull-black fungus that can grow on the leaves, fruit and stems of indoor and outdoor plants. The fungus is easy to identify by its “sooty” appearance. Light infestations may begin at the base of leaves and move toward the tips. Heavy infestations can cause the entire plant to appear black.

Sooty mold is caused by the presence of aphids, mealybugs, soft scale and whiteflies. These insect pests have mouthparts that suck plant juices, and as waste, they secrete a sweet substance known as honeydew. The honeydew lays on plant surfaces and over time grows into this specific mold.

Since almost all plants are susceptible to aphids, mealybugs and whiteflies, it stands to reason that almost all plants are susceptible to sooty mold. Crepe myrtles, hollies and azaleas are just a few of the numerous landscape plants that you may find covered with the fungus. You’re most likely to find sooty mold in the landscape in spring and summer, when insects are the most active.

On houseplants, sooty mold can be present and active any time of year. You’ll often find it on your houseplant before you spot the insect problem. (If you see sooty mold on a Ficus or other houseplant and you don’t see any obvious insects, look along the stems, and you’re likely to find soft scale insects camouflaged there.)

Warnings
  • Before using any insecticide, check the product label to answer these questions:
    1. Does the product list the specific insect I need to control?:
    2. Can it be used on the plant I need to treat?:
    3. Can it be used where I need to spray (i.e., near a pond, in the house, next to fruit trees, etc.)?:
    If you answer “No” or “I don’t know” to any of these questions, check with your local Extension Service to find the appropriate chemical to use on your plant.
  • It’s illegal to apply chemicals in a manner – or to a plant – that’s not listed on a chemical label.
Tips
  • Controlling the insect that causes sooty mold will probably take more than one chemical application. After spraying, recheck the plant in one week to see if you can spot any remaining live insects. Continue this process until the insects are eradicated or reduced to a manageable level.
Faqs
  • Q: Does sooty mold keep my plants from flowering?
    A: No. The insect causing the sooty mold is likely damaging delicate plant tissue as it feeds, and that’s what’s keeping your flowers from forming or causing them to grow with a distorted appearance.
 
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Articles
  • All About Aphids
    Aphids those commonly found insects in your garden are easily controlled with simple techniques.
  • All About Mealybugs
    Learn how to identify what mealybugs are by understanding their life cycle and the damage they cause, as well as learn how to control these plant pests.
  • All About Scale
    Learn how to identify what scales are, the damage they cause and how to control these garden pests.
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