Yellow substance on Dracaena Compacta Planter. Should I be concerned?

Question

This is a post from Bangalore(India) (Temp: 20-30°C; Humidity: 75%)

I recently noticed some yellow stuff on the planter(terracotta) of my Dracaena Compacta. Along with this with the plant also seems to be not looking so great overall, I'd like to understand if this could be related. Some follow-up questions:

1. Could the fungal infection spread while wiping the leaves?
2. Should the leaves be cut off from the plant?
3. Is it recommended to use a Fungicide? Some pictures of the pot:

Below are some pictures of the problems I see on the plant:

Under some leaves:

Background:

1. This plant is placed in a corner of a well lit room with no direct light falling on it.
2. The air movement may not be too much in that area because it is a corner.
3. There aren't any other diseased plants around this.
4. The leaves are sticky to the touch. As it may contain some residue of some neem oil that was applied onto the plant around 5 months ago. The concentration of the neem oil may have been a bit more than recommended.
5. The plant is watered only when the soil dries out largely.
6. Reverse Osmosis (RO) water is used to water this plant.

I would like to know whether the yellow stuff on the pot is related to the yellow spots on the leaves of the plant.

The plant's health seems to be on a steady decline.

I would like some help in diagnosing this problem and planning my next steps accordingly.

Thanks in advance.

Answer 1

There are several things going on with this plant at the same time:

• the yellow stuff on the pot is salts that are crystallizing on the porous clay surface. You should be able to brush them off leaving a dry yellow powder. This is harmless to the plant
• in the last picture I see a whitish substance on the leaves which is probably pesticide residue or dried salts from overhead watering at the growers. This is harmless to the plant and can be removed with a damp cloth
• the brown and yellow spots on the leaves are a fungal infection caused by overwatering. If there is no drainage in the pot or it is watered too much the water forces the air out of the soil creating an anerobic environment which is perfect for fungus. Once this gets established it moves upstairs into the leaves. You can verify this by confirming it does not rub off and the pattern is to have a dead or necrotic brown area surrounded by a yellow circle of new growth. Often the dead areas will be more common on older growth. Plants can outgrow this if they have good drainage and the top of soil is allowed to dry out to a one inch ( ~2 Cm) depth before watering again
• finally the plant appears to have soft bodied insects on it. Make a solution of 5 ml of dish soap to 1 liter of water. Rinse a cloth or rag in the solution and wipe down every leaf, top and bottom. Spray with fresh water after a few minutes. Repeat at least twice at five day intervals to catch any new adults that have hatched from eggs.

That's a lot of diagnosis, the most important thing is not to overwater these plants.

You asked

1. Could the fungal infection spread while wiping the leaves? No, the fungus is inside the leaf

2. Should the leaves be cut off from the plant? You can to make it look better but it will not help or hinder the infection

3. Is it recommended to use a Fungicide? Where I live no fungicides are available. Benlate or Benomyl used to be available many years ago. You can control this by watering less or providing more light