Be Gone, Black Shrub Mold

Pest ControlPlants

Black sooty mold is a fungus that covers leaves, stems, and fruit. It grows on honeydew, a sugary substance produced by insects such as whiteflies and mealybugs. Manage these pests and prevent further infestations with insecticide applications and proper cultural practices.

Have you noticed a black fungus growing on the leaves of your landscape plants? Sooty mold looks like black powder or stain that coats leaves, stems, and even fruit. Keep calm; your plants are not done for. The presence of black sooty mold is common in the summertime in Florida, and there are ways to eradicate it and prevent it.

What is Black Sooty Mold?

Black sooty mold, or Capnodium, is a fungus that grows on honeydew, a sugary substance found on plant parts and produced by certain insects. Aphids, whiteflies, mealybugs, and soft-body pests are all responsible for honeydew production. These insects consume juices from plant tissue and excrete sticky honeydew, which covers leaves, stems, and fruit. Fungus grows on the honeydew and creates a layer of dark, sooty mold that, while not directly damaging plants, keeps sunlight from reaching leaves and slows plant growth.

How to Get Rid of Sooty Mold

A mixture of water and natural detergent will help to wash off sooty mold. Wet the entire plant (including the undersides of the leaves), leave it alone for a few minutes, then spray off the soapy solution with water. You may need to do this several times to thoroughly wash off the mold.

After you have removed the mold, look for damage that may have been done by soft-bodied insects. Remove any badly damaged leaves or plant parts.

The key to getting rid of Capnodium, however, is to control the insects producing honeydew. The black fungus will not go away if pests are still a problem. Use an insecticidal soap or horticultural oil (like neem oil) to treat the insects. Spray every part of the plant, from stem to leaf, making sure to wet the leaves’ undersides. Follow the directions on the label for repeat treatments.

Cultural Practices to Prevent Infestations

Once you rid your plants of an insect infestation, adopt proper cultural practices to help keep the pests away. Following are several cultural practices to incorporate into your landscape care:

  1. Fertilize, water, and prune only when needed. In excess, these practices stimulate new growth, which draws these insects. Refrain from pruning altogether while the plants are dormant.
  2. Scout your landscape for pests and apply a spot treatment immediately. If the insect population is small enough, manually remove the pests by picking them off or spraying them with a hose.
  3. Be on the lookout for ants on leaves and stems. Ants feed on honeydew, so the presence of ants may signal that the honeydew-producing pests are present. Examine plants for trouble insects.
  4. If you identify a cluster of pests, trim off the affected branches to remove them from the plant entirely. 
  5. Plant natural repellents like garlic and onions around your other landscape plants to keep the plant-sucking insects away.
  6. Plant flowers like dahlias, zinnias, asters, and cosmos to attract the pests and keep them away from your shrubs and citrus trees.

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