Which of the following is not a viral disease of plants?

Options

A. Red rot of sugarcane
B. Tobacco mosaic disease
C. Leaf curl of tomato
D. Tristeza diseases of citrus

Explanation

To determine which of the following is not a viral disease of plants, we will analyze each option provided:

1. **Red Rot of Sugarcane**:
- This disease is caused by a fungus, specifically the *Colletotrichum falcatum*.
- Symptoms include reddening of the stem, mushy fungal growth, and yellowing and drying of leaves.
- Since it is caused by a fungus, it is not a viral disease.

2. **Tobacco Mosaic Disease**:
- This disease is caused by the Tobacco Mosaic Virus (TMV), which is a viral pathogen.
- It affects various plants and is characterized by leaf discoloration and a mosaic pattern on the leaves.
- This is a viral disease.

3. **Leaf Curl of Tomato**:
- This disease is caused by the Tomato Yellow Leaf Curl Virus, which is also a viral pathogen.
- Symptoms include curling of the leaves and stunted growth.
- This is a viral disease.

4. **Tristeza Disease of Citrus**:
- This disease is caused by the Tristeza virus, which affects citrus plants.
- Symptoms can vary but often include yellowing of leaves and stunted growth.
- This is a viral disease.

After analyzing all the options, we conclude that:

**The correct answer is: Red Rot of Sugarcane (Option A), as it is caused by a fungus and not a virus.**