Dracena – Disease
Q: Our corn plant has oval shaped yellow spots with dark centers on it’s leaves. What is wrong with it and how do we remedy the problem?
A: I’ve had my corn plant for about 12 years and I’ve never seen any problem such as that. From your description, it sounds as if it is a fungus. I do know that corn plants (Dracaena) are sensitive to fluoride levels in tap water.
I found a good publication from Penn State on the diseases of corn plants.
Also, here is a University of Georgia publication on general houseplant care:
If you decide to use a pesticide on your plant, either take it outside on a warm day and wait until it is dry or place it in a bathtub for spraying. Follow the label instructions carefully.
see also Diseases of Houseplants