Powdery mildew is caused by which type of organism?

• A. Bacteria
• B. Nematodes
• C. Fungi
• D. Virus

Answer: (C)

Powdery mildew is caused by fungi. These diseases are caused by a group of fungi known as powdery mildews that colonize the surface of leaves and stems, forming a white, powdery coating of hyphae and conidia. They don’t typically destroy tissue by digging in like some bacteria do, but they feed on living plant cells by specialized structures called haustoria, which allows the white coating to spread across the surface.

This is different from bacteria, which often create spots, rots, or slime on plant tissue; nematodes, which are microscopic roundworms that usually attack roots or form galls, not surface powdery growth; and viruses, which cause mottling, mosaic patterns, stunting, or leaf distortion rather than a superficial powdery film. The telltale white powder on leaves and stems is characteristic of a fungal pathogen, not the other groups.