# Ask for evidence before approving treatment

Lesson 2 of [Buy and oversee tree care work](https://arborists.fyi/academy/buy-tree-care-work.md), 12 minutes.

Leaves changing colour are a reason to investigate, not a complete diagnosis. University of Missouri Extension explains that leaf scorch can result when leaves lose water faster than roots can replace it. Site conditions and root problems can contribute, while some diseases can produce similar effec…

The rest of this lesson is for learners enrolled in the course. [See how Buy and oversee tree care work works](https://arborists.fyi/academy/buy-tree-care-work.md).

Also on the [web page](https://arborists.fyi/academy/buy-tree-care-work/ask-for-diagnostic-evidence).