Short answer
The sticky residue on your Bird of Paradise is almost certainly honeydew, a sugary substance excreted by sap-sucking pests like scale or mealybugs. The most common fix is to thoroughly wipe the leaves with a damp cloth and treat the plant with systemic insecticide or neem oil to eliminate the infestation.
Finding sticky, clear droplets on your Strelitzia nicolai—often referred to as honeydew—is a clear sign that pests are feeding on the plant's sap. While Bird of Paradise plants are robust, this residue can attract sooty mold, so it is important to address the underlying infestation before it spreads to other areas of the plant or nearby foliage.
Scale appear as small, hard, brown bumps on the undersides of leaves or along the sturdy stalks. These insects hide effectively, often allowing a heavy sticky residue to accumulate on the foliage below before they are spotted.
Check: Look for small, immovable brown bumps on the stems or leaf undersides that can be scraped off with a fingernail.
Fix: Manually scrape off visible scale with a soft toothbrush or cloth dipped in rubbing alcohol and apply a horticultural oil or systemic insecticide.
Mealybugs look like tiny tufts of white, cottony fluff and are frequently found in the tight crevices where the large Strelitzia leaves meet the main stem. They consume sap and excrete large amounts of honeydew, which makes the plant surfaces feel tacky or sticky.
Check: Check the leaf axils and undersides for white, cotton-like masses.
Fix: Spot-treat clusters with a cotton swab dipped in isopropyl alcohol and treat the entire plant with insecticidal soap every 7 days until clear.
While less frequent on the thick, waxy foliage of an indoor Bird of Paradise, aphids can target tender new growth. They cluster on unfurling leaves and quickly produce sticky honeydew as they feed.
Check: Examine the base of emerging leaves for clusters of tiny, green or black soft-bodied insects.
Fix: Gently spray the plant with water to dislodge them and follow up with a mild application of insecticidal soap.
When to worry
If you notice the leaves beginning to turn yellow or develop black, dusty spots of sooty mold, the infestation is severe and requires immediate treatment to prevent long-term foliage damage.
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Diagnose my Bird of ParadiseThe honeydew itself is non-toxic, but the substances used to treat the infestation, such as insecticides, can be harmful; keep pets away from the plant during and after treatment.
Washing the leaves helps remove the residue and mold, but it will not kill the insects themselves. You must use a treatment like insecticidal soap or alcohol to stop the production of new honeydew.
Only prune leaves if they are heavily infested or dying; otherwise, wipe them down thoroughly and keep the plant in good health so it can focus energy on recovering.
Consistent with guidance from: Royal Horticultural Society, University of California Agriculture and Natural Resources.