There isn't one specific name for a "plant doctor" in the same way there is for a human doctor. However, depending on the context and what kind of plant issues they deal with, you could call them:

* Plant Pathologist: This is a scientist who studies diseases affecting plants.

* Horticulturist: A specialist in the cultivation of plants.

* Botanist: A scientist who studies plants.

* Arborist: A professional who cares for trees.

* Green Thumb: A casual term for someone with a knack for growing plants.

If you are looking for someone to diagnose and treat problems with your plants, you can usually find them at a local garden center, nursery, or by searching online for "plant care specialists" or "plant doctors" in your area.