Fungal? Extra-floral nectaries? - Ask Extension
Hi there, thank you for your time! This philodendron white princess has been getting these spots for a few months. They are not powdery nor sticky. Pe...
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Fungal? Extra-floral nectaries? #923074
Asked December 24, 2025, 12:42 PM EST
Hi there, thank you for your time! This philodendron white princess has been getting these spots for a few months. They are not powdery nor sticky. Pests have been extensively searched for, and found none. It is kept in an IKEA greenhouse cabinet, with a little fan, but maybe not enough airflow? The spots come in with that dark brown color. Do you have any idea what this could be? Thank you again for looking at this.
Multnomah County Oregon
Expert Response
Leaf spots on the Philodendron probably indicate too much humidity. I found references to bacterial leaf spot and bacterial blight here, from PennState Extension. Advice is generally to remove leaves with spots and/or buy plants that are clear of disease.
Philodendron generally do well in average home humidity, but over 60% is best (see here). Judging the humidity levels in your glass case is a challenge and while there are measuring devices for greenhouses, that might be more expense than you want. I grow closed terrariums and watch the vapor development. A bit of fogging daily, usually in mornings, is good. But if there are big water drops remaining all day on the glass, or if plant leaves remain wet, I air out the container.
This could be a fungal issue, but I don’t find much about that on Philodendron. And anyway, reducing humidity is the recommendation for fungal problems too.
Lastly, I don’t find recommendations about the fan, only to keep Philodendrons out of cold drafts. Is the case warm enough?
Houseplant problems are hard to troubleshoot, with so many variables. I hope your plant pulls through.
Philodendron generally do well in average home humidity, but over 60% is best (see here). Judging the humidity levels in your glass case is a challenge and while there are measuring devices for greenhouses, that might be more expense than you want. I grow closed terrariums and watch the vapor development. A bit of fogging daily, usually in mornings, is good. But if there are big water drops remaining all day on the glass, or if plant leaves remain wet, I air out the container.
This could be a fungal issue, but I don’t find much about that on Philodendron. And anyway, reducing humidity is the recommendation for fungal problems too.
Lastly, I don’t find recommendations about the fan, only to keep Philodendrons out of cold drafts. Is the case warm enough?
Houseplant problems are hard to troubleshoot, with so many variables. I hope your plant pulls through.
