Yellows diseases in plants are caused by what type of organism?

• A. Mycoplasma (wall-less bacteria)
• B. Fungi
• C. Viruses
• D. Nematodes

Answer: (A)

Yellows diseases are caused by wall-less, bacteria-like organisms that live in the plant’s phloem and disrupt the movement of nutrients through the tissue. These organisms are phytoplasmas, historically called mycoplasma-like organisms, which matches the description of Mycoplasma (wall-less bacteria). They are not fungi, viruses, or nematodes, which produce disease symptoms through other mechanisms. Phytoplasmas rely on sap-feeding insects, like leafhoppers, to spread from plant to plant, so managing these diseases often focuses on controlling the insect vectors and removing infected plants to limit spread.