Dirty Looking Hibiscus Leaves?

Question:

My Hibiscus leaves on some varieties look dirty (maybe insect dirt) and grayish. Generally unhealthy, like they have been stung or like they have a disease.

Hardiness Zone: 9a

Jesse from Winter Haven, FL

Answer:

Jesse,

I cannot say for sure what is happening to your hibiscus, but here are a few ideas.

1. If the leaves on your hibiscus are covered in a grayish-white powdery substance, you may be looking at a fungal disease called powdery mildew. If this is the case, destroy the infected leaves and rinse the remaining foliage to remove any leftover spores and make sure your plants are getting enough air circulation. Spray your hibiscus with a solution of baking soda, vegetable oil and water (2 tablespoons of baking soda, 1 tablespoon of vegetable oil and 1 gallon of warm water). Do this once a week for several weeks to prevent further spread of the disease and also as a preventative measure.

2. If the leaves are covered in a more black or dark gray sooty-looking powder, your plants probably have sooty mold. This also points to an aphid infestation, because sooty mold forms on their droppings. Destroy infected leaves and use strong jets of water from your garden hose to blast away aphids or spray control them with an insecticidal soap.
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3. Rust or orange-colored deposits are rust. Destroy infected leaves and control with an organic sulfur fungicide.

Ellen