Answer: I apologize for the delay in answering your question. Unfortunately, based on your description I am not able to diagnose your problem specifically. Philodendrons are potentially susceptible to a number of bacterial diseases, this sounds like it might be Xanthomonas leaf spot but it is very difficult to diagnose this type of problem long distance. If it is just on a leaf or two I would suggest you carefully remove the affected leaves and put them in the trash being careful not to touch any other leaves with them. Then wash your hands thoroughly -- or wear disposable rubber gloves when you handle the infected leaves. Avoid pruning the plant while there are signs of infection. Also make sure the plant has good air circulation and avoid wetting the leaves when you water it to try to prevent spreading the disease. If that does not stop it, you may want to consult with your local county extension to obtain a definite diagnosis. If it is something that can be controlled, they will have the most up to date recommendations on what to use and how/when to use it. I'm sorry you are having trouble with your plant.
Q&A Library Searching Tips