leaves on barberry turning brown
The leaves are turning brown and falling off. What's wrong?
There are many possible causes for brown leaves, and your plant is depending on your abilities as a detective to figure out what's going on. First question, is this a new plant, or an established one? If it's new, brown leaves may well have something to do with the stress of transplanting, water (too much or too little,) or light (again, too much or too little.) Talk to the store where you got the plant for their advice.
If this is an older plant, think first if something in the environment has changed -- water or light or herbicide from somewhere. Then check the general management against this article: https://www.gardeningknowhow.com/ornamental/shrubs/barberry/barberry-shrub-care-tips.htm
If everything looks all right here, examine the leaves and branches for disease or insects. Here are a couple of articles to help you: https://www.gardeningknowhow.com/plant-problems/disease/leaf-browning-in-center.htm
If you're still at a loss, you can take some leaf, branch, and soil samples to the county extension service. This link will help you locate one: