While begonias are relatively resistant to pests and diseases, they can still encounter problems from time to time. Keep an eye out for common pests like aphids, spider mites, and thrips, especially if you notice sticky residue on the leaves or distorted growth. If pests are present, treat your plants with insecticidal soap or neem oil according to the manufacturer's instructions. Healthy begonias exhibit vibrant and lush foliage. Look for plants with well-formed leaves that are free from discoloration, spots, or signs of wilting. Avoid plants with yellow or brown leaves, as these may indicate stress or disease.