I have a Phalaenopsis that's had sticky leaves for about a month now, almost like they have a viscous coating on them. I don't see any spiders or actual insects, but I'm wondering if it could be scale insects or if it's just condensation. Should I do something about it?
It's not condensation - that sticky stuff is almost definitely honeydew, which is what parasites like scale insects, aphids, or spider mites secrete when they suck the sap, even if you can't see them well with the naked eye. Check the underside of the leaves and around the leaf axils (where the leaves attach to the stem) with a magnifying glass, because they often hide there, especially scale insects which are tiny and brown. If you find anything, wipe the leaves with a cotton ball dampened with alcohol or soapy water, repeat the treatment every 3-4 days for a couple of weeks, and increase the humidity around the plant because these insects hate air that's too humid.
Sticky leaves on an orchid are almost always a sign of pests, not condensation. What you're probably seeing is honeydew, a sugary substance that insects leave behind as they feed. Scale insects are the most common culprit - you often don't see them because they're tiny or they hide under leaves and along stems. Check the underside of the leaves really carefully, the leaf axils, and the base of the leaves with a magnifying glass if you can. Look for small white, brown, or grayish-green dots that seem stuck to the plant.
Another possibility is aphids or whiteflies, though they're less common on orchids. If you see a gray or black coating on the leaves (sooty mold), that's a consequence of the honeydew and means the infestation is already pretty advanced. This isn't the time to wait around: clean all the leaves with a cotton ball dampened with rubbing alcohol, really going over the undersides and the corners. Do this every 3-4 days for about two weeks, then switch to a scale spray (organic options work fine) if things don't improve.
In the meantime, isolate the orchid from your other plants if you can, because these pests spread easily. Increase the airflow around the plant a bit and avoid watering it too much: pests prefer humid, stagnant environments. If after a month things haven't changed, then yeah, it's worth getting someone more specialized to take a look, but in most cases the manual intervention with alcohol does the trick.
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