Lemon trees are affected by a variety of pests, including Asian citrus leafminers, citrus rust mites, mealybugs, spider mites, scale insects and blackflies. According to Julian W. Sauls, most insects cause little to no harm and do not need to be treated. Insects that will damage or destroy your lemon trees are virtually impossible to control in a home garden. Most insects can be ignored, and using insecticides or pesticides can cause harm and kill good parasites that help lemon trees thrive.
Download a resource such as "The Natural Citrus Growers Free Guide" (see link under Resources), or purchase a book that identifies lemon tree pests with pictures. Amazon.com has several books on caring for citrus trees. Search under books with the keywords "citrus tree care."
Collect a sample of the pest on your lemon tree.
Compare sample to pictures in your resource.
Identify whether any actions are needed to protect your lemon tree from this pest.
Lemon tree pests are often harmless. Identifying pests can help you learn what is in your garden, and it may help you determine whether any of your other trees or plants are at risk.
Insecticides can destroy natural parasites and do more harm than good to your lemon trees and other members of your garden. Use only when needed.