If you grow hibiscus and some of your leaves develop scary-looking spots, try not to panic! While they might appear ominous, these spots are usually not a cause for alarm, and they often clear up on their own.
These spots can be ugly. But, treatment will help restore your plant to a happy, healthy state.
Of all the pests and diseases that can affect Hibiscus plants, spots on leaves are relatively harmless.
We share tips on what causes the discoloration, how it affects the plant, and how to treat it with success.
What Conditions Cause Black Spots on Hibiscus?
Black or brown spots on buds or leaves of Hibiscus often come from two problems:
- An overgrowth of bacteria and fungus
- Pest infestation
Bacterial and fungal spots arise when the plant stays moist for long periods and isn’t allowed to dry out.
They tend to occur during cool, damp weather. You will recognize them by characteristic dark discolorations within the flesh of the green leaves or flowers.
The microbes responsible usually don’t affect the plant or cause other symptoms.
The other possibility is a scale, aphid, white fly, or other insect infestation.
Scale and aphids excrete a sticky waste substance called honeydew. The honeydew can encourage sooty mold growth.
This type of mold usually shows up as a black, soot-like coating on the plant’s leaves and stems.
Do Black Spots Damage the Plant?
Regardless of what’s causing the spotting on hibiscus leaves they typically don’t hurt the plant.
Bacterial and fungal infections usually stay confined to a few leaves. They are not likely to spread to the rest of your hibiscus. In these cases, the damage to the plant is cosmetic.
If the plant has sooty mold, the fungus feeds on insect secretions, not the actual plant tissues. The leaves themselves are not damaged.
If enough mold grows, it can prevent photosynthesis and block sunlight from reaching the leaves. Over time this can harm the plant’s health.
Sooty mold almost always means garden pests have taken over your hibiscus.
Pests are a big problem for gardeners because they can harm or kill plants. They cause damage by:
- Eating holes in leaves, stems, and roots
- Hibiscus aphids or Pink Hibiscus mealybug sucking sap from plant tissues
- Laying eggs on the plant
- Transmitting plant diseases
As you can see, fungal leaf spots on hibiscus aren’t a problem in and of themselves. But in the case of pest infestations, they can be a symptom of a larger and more serious issue.
More on Hibiscus Pests:
How To Control Spots on Leaves Of Hibiscus
When spotting is due to bacterial or fungal activity, treatment isn’t always necessary. The microbes generally don’t affect the plant on a systemic level or cause other symptoms.
When the temperatures turn warm and dry the bacteria and fungus should die a natural death. The affected leaves will fall away from the plant.
If your local climate stays wet and moist year-round or you want to get rid of spots faster, trim away infected leaves.
Or spray with an anti-microbial product such as neem oil or Bayer Advanced 3-in-1.
Using an anti-fungal spray also helps ensure that fungus won’t spread elsewhere on the plant.
Improve the Cultural Conditions
- Dispose of unhealthy plant material to avoid spreading disease pathogen throughout your garden.
- For general preventive care, improve air circulation by pruning branches and leaves from the plant.
- Water hibiscus at the soil level instead of overhead. Watering directly on leaves can encourage microbial growth.
Pest infestations are more challenging to manage. To treat sooty black mold, you need to stop the problem at its source and get rid of the insects that are causing it to grow.
Horticultural oil or neem oil can kill the insects. But, severe infestations may need a stronger chemical pesticide to kill the pests.
Usually, it’s best to aggressively treat an infestation so the problem doesn’t continue to get worse.
Prevent future infestations through companion planting or introducing beneficial insects (like ladybugs) to your garden.
Once you’ve gotten rid of any pests, wash honeydew and sooty mold off the leaves using insecticidal soap.
It may take some time for the plant to recover from an infestation, but you shouldn’t see any new mold growth once it does.