The answer to 'why is my shrub pests' is that your shrub may be infested with insects or other pests. Common causes of shrub pests include aphids, spider mites, scale insects, and caterpillars. These pests can feed on the leaves, stems, and roots of your shrub, causing damage and stunted growth.
Symptoms of shrub pests may include discolored or wilting leaves, sticky residue on the plant, and the presence of the pests themselves. To solve the problem, you'll need to identify the specific pest and then use the appropriate control method, such as applying insecticidal soap, horticultural oil, or introducing natural predators.