Lime Tree Bugs
I've got a lime tree in a 40-gallon pot and it's getting these white with gray-striped things on the branches that almost look like little sea shells. Also, it's starting to turn the stalks black.
Sounds like scale. The following articdle should help: https://www.gardeningknowhow.com/plant-problems/pests/scale-bug-how-to-control-plant-scale.htm