Noticed Sticky Plant Leaves? This Often-Missed Pest Could Be the Reason

Sticky plant leaves are something no indoor gardener wants to see on the plants in their collection. That’s because that clear, tacky substance, which may also appear on nearby surfaces, is a telltale sign that insect pests have been chowing down on your plants.

Here’s what to do if you encounter sticky leaves on your houseplants, including tips for eliminating the pests and making your own insecticidal soap at home.

What Causes Sticky Plant Leaves

Sticky plant leaves are caused by insect pests, which excrete a clear, sugary substance as they suck the sap out of plant parts. Over time, the stickiness builds up on leaves and stems as well as tables, shelves, and floors around plants.

Because sap-sucking insects tend to feed in groups, sticky plant leaves can seem to appear overnight. When you see them, the culprits are typically found nearby.

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What Is Honeydew?

The clear, shiny, sticky substance that appears on plant parts and surrounding surfaces due to pest activity is called honeydew. Insects like aphids, mealybugs, and scale leave this substance behind, as do outdoor plant pests like spotted lanternflies.

Honeydew itself isn’t harmful to your plants, but it’s a sign that you have a pest problem that needs immediate attention to avoid further damage to your plants.

Without treatment, a severe buildup of honeydew can cause a fungal disease called sooty mold to grow on leaves, blocking sunlight and stunting plant growth. Honeydew and sooty mold can be controlled by managing insect pests on houseplants.

Pests like aphids can affect even the healthiest houseplants, but there are a couple of different things you can do to prevent pest damage and sticky plant leaves before they occur. Quarantine new plants for a couple of weeks in a separate room.

Watch for signs of pests or pretreat new plants for insects before introducing them to the rest of your collection.

Another way to ward off pest activity is to ensure that plants are receiving the light, water, and growing conditions they need to thrive. Some pests, like spider mites, tend to attack plants that are already stressed.

How to Fix Sticky Plant Leaves

1. Inspect the leaves. Carefully inspect your plant’s leaves and stems as well as the surrounding surfaces. Note areas that are covered in sticky honeydew or black sooty mold, as pests are likely to be feeding nearby. If possible, try to identify the houseplant pest or pests causing the problem, which can help determine how to treat the issue.
2. Remove impacted leaves. Use clean, sharp pruners or shears to remove dead or dying leaves that have been affected by pest damage. These leaves may have yellow or brown tips or edges or show other signs of pest damage, like curling leaves or tiny holes from the sucking insects.
3. Spray with water. Spray the plant thoroughly with a strong jet of water from a hose or shower, which can help knock off some types of insect pests. Be sure to spray the undersides of leaves and in the spaces where leaves and stems meet.
4. Wipe leaves clean. Wipe plant leaves and affected surfaces with a damp cloth and mild soap to remove honeydew and any sooty mold.
5. Pick off pests. Hand-remove pests like scale or mealybugs by dipping a cotton swab in rubbing alcohol and dabbing plants off of leaves.
6. Treat with insecticidal soap. Spritz the entire plant with insecticidal soap. Ensure that the spray wets the bodies of any insect pests you can see. You can purchase these plant-safe soaps from a garden center or hardware store, or you can make your own by mixing a couple of tablespoons of Murphy Oil Soap or castile soap with one quart of water.
7. Repot. Repot affected plants in fresh soil. Rinse away loose soil from pots and plant roots before repotting.
8. Re-treat weekly. Re-treat infested plants with insecticidal soap every four to seven days to reduce pest populations.