Philodendron Selloum (Lacy Tree); 9″ pot; yellow leaf edges turning brown and dry, small round black plaques on some stems and leaves (these can be picked off); by itself near center of large room with east facing patio doors on one side and west facing bay window one the other (bright indirect light); purchased at ALDI supermarket in April so never repotted.
A week ago I purchased a Ornithogalum Dubium plant on sale at a Walmart. I put it in a bright window with my African violets. Today I discovered all my violets were infested with aphids and the O.D. had webs as well as insects, indicating spider mites. Yikes! I threw them all out and began to inspect all my houseplants. I’d noticed the yellowing edges on a couple of the philo leaves, but today I saw the plaques as well. I can’t find any images of these online. I hope you can advise me, and many thanks in advance.
From your description, your Selloum has a scale insect infestation. Scales appear as dark, slightly raised bumps about the size of match heads. They can be scraped off easily with a fingernail leaving a soft white or crusty white reside behind. When the scales are young and active, they secrete a sticky residue called honeydew on the tops of leaf surfaces below them. If you are not finding any stickiness, then it is likely that the scales are dead and only the carcasses remain. They are not harmful.
If you suspect live scales, then mix a solution of one part rubbing alcohol, 5 parts water and a squirt of liquid dish soap. Then, thoroughly spray ALL leaf and stem surfaces of the plant until they are dripping wet. This is a messy process best done outside. Thoroughness of coverage is critical to success. The scale juveniles are translucent and very hard to see and it is important that the spray makes direct contact with each one of them. After spraying, use a paper towel, sponge or soft cloth to wipe away the visible scales.
Thank you very much. Are the brown edges on a few of the leaves also caused by the scale insects? I don’t see evidence of sticky residue so far.
The brown leaf edges are unrelated to the scale. Inadequate light and improper watering are the most common causes of this symptom. Your Selloum should be no more than 5 feet from the nearest uncovered sunny window. Allow the top 1-2 inches of soil to dry in between thorough waterings. Make sure the pot has drain holes. If your tap water is hard, use filtered or distilled water. If you are fertilizing, stop.