Is this a disease? Do I have to cut this leaf? If so where is the best? From the base or just the leaf? It is in the same situations from days, without any progress, but I don't know what is better to do.
This is fungus/bacteria/virus on an Anthurium which is brought on by the root ball being too wet for too long. An anerobic agent finds wet, dark and no oxygen to be a great place to live and then moves up the plant to the leaves. Key identification points which work across many species are:
- older leaves affected first
- starts as a small yellow area which becomes black as the tissue dies
- rings of growth: in the picture you can see the initial area of growth which has died and the tissue has dried up, then surrounding it are rings where the agent has grown for a while then stopped
Good news is that most plants can out grow this without any treatment if you follow a few simple steps:
- provide more light (for Anthuriums, bright filtered light)
- ensure the plant is not sitting in water
- keep the plant drier
- optionally remove the damaged leaves
You may wish to repot the plant with a soilless mix that is high in organic matter. You can just put new soil in the bottom of the pot and cut a small portion of the root ball off at the bottom. Do not put stones in the bottom of the pot. This is also a good time not to experiment and use top soil. Use a sterilized potting soil high in organic matter like peat or coir.