Yellow/brown spots on Monstera

Question

For a couple of months, small black spots have been slowly spreading on two of the leaves of my Monstera. On one leaf, they got worse, and ringed with yellow, then suddenly the leaf died.

The black spots are physically on the surface of the leaf, and can be scraped off. I tried wiping the leaves with bicarb soda (maybe for no good reason) but it didn't seem to help.

Now, the badly affected leaf has suddenly turned yellow and died.

Is there anything I can do to prevent this happening to the other two leaves? I don't think I'm overwatering - if anything, perhaps the opposite. I check the soil is dry before I water.

Answer 1

It sounds/looks like your plant has a fungal leaf spot problem. The little black spots are called fruiting centers. That is where the fungus creates and sends out new fungal spores to infect other parts of the leaf and spread to new leaves. Stop scraping off the black spots! You are only helping new fungal spores to get airborne.

Fungus problems can often easily be solved by spraying the leaves with Lysol. It won't cure the spots that are already on the affected leaves but it can stop the fungus from fruiting spores and prevent the spots from spreading to unaffected leaves. Remove the heavily infected leaves as soon as possible. The other lightly infected leaves can be removed once the plant starts producing new leaves. You will need to spray the leaves with Lysol about twice a week until there are no more leaves with fungal spots.

Any type of improper watering, under-watering as well as over-watering, can make a plant stressed and more susceptible to disease and harmful insects. As a general rule, allow the top 1 inch of the soil to dry before watering.