Is this plant diseased?
I have had this houseplant for probably 20 yrs. It has been very healthy. I have noticed the leaves starting to look like they have dark brown spots within the leaf structure (the surface top and back side are smooth), that eventually turn the leaves yellow to brown and then completely die.They come in nice and green, but change in matter of weeks. Is it old, undernourished or diseased? What if anything is the solution? Note: (pictures below) 1. Front of leaf; 2. Back of leaf; 3. Whole plant.
Marion County Oregon
Hi and thanks for contacting Ask an Expert. Since you have had this plant so many years, you likely know how to water it, keeping it moist but not letting it dry out. And it needs light but not a lot of heat again, it looks like you have it in a good location.
The spots look like fungus and the underside of one of the leaves looks like it is drying out again due to fungus. I do not think this is a nutrient deficiency. There are several fungicides that will take care of this fungus. Neem oil (only purchase 100% pure Neem - find it online) and possibly Seranade which is a bacteria that eats fungi.
Remove the damaged leaves down to the soil level and dispose of them. Spray using the container directions both top and bottom of the leaves. Neem will also kill any insects (white flies and aphids and gnats for indoor plants) on the plant.
I would use a liquid fertilizer that is not synthetically made such as Fish Emulsion, cut 1/2 to 1/4 strength to give the plant a little added food. If this plant has recently been moved from its normal location, you should put it back.
Watering should be done in the sink and water with distilled water instead of tap water. Distilled water does not contain salts. Watering until the pot drains flushes out salt build up.
If after a few weeks this continues to be a problem, please re-contact us. Your photos have been very helpful in answering this question.