Some common problems with boxwood shrubs include twig blight, root rot and insect damage. Extreme weather can also damage the plants and lead to unattractive features.
Twig blight, which is a result of certain fungi and nematodes in the soil, causes the shrubs to turn yellow and appear weak. Thin and prune the plants to help resolve the problem. Root rot turns the leaves light green before killing the plant. Adding fungicide to the soil can effectively prevent it from occurring. Remove any dead leaves and branches from the ground as soon as possible. Insects such as the boxwood leafminer are also harmful to the shrubs. Inseticidal sprays that are designed specifically for boxwood pests can help control the bugs.