Lemon trees are grown throughout the southern United States, including Florida, Texas, Arizona and California, and may also be grown as container plants in the north, where they are grown indoors during the winter. They are the most cold tender of any citrus tree, according to Texas A&M University. They are vulnerable to the same pests as other citrus trees, but are rarely significantly damaged.
Positively identifying lemon pests requires growers to consider the symptoms, the time of year, and to visually inspect the insect if available.
Rust-colored rinds are caused by citrus rust mite; removable, colored, raised spots on fruit and leaves are caused by scale insects. Cottony masses near the stems may be caused by scale or mealybug. Curled leaves are the work of aphids, while silver scratches on leaves are caused by spider mites. Spirals of eggs or small black insects are blackfly. Asian citrus leaf miner attacks new leaves, chewing holes in the leaves in a serpentine pattern.
The time of year damage occurs is often a clue to the problem. Scale insects and mealybugs are most apparent during the summer. Aphids attack lemon trees during each flush of growth. Whiteflies and spider mites infest lemon trees from spring to fall, while blackflies can be a problem any time.
Few insecticidal treatments are available to home growers, according to Texas A&M University, and lemon trees are seldom killed by an insect infestation, although yields may be limited or lemon quality diminished. If spraying is warranted, ensure that the insect has been positively identified and protocols for proper spraying are followed. Most problems are best ignored, advises Texas A&M University, "minimizing damage to the complex of beneficial organisms that exist in citrus."
All plants, including lemon trees, are better able to withstand insect invasions when they are healthy. Lemons need well-drained soil and a sunny location. They should be watered at least every two weeks in dry areas and fertilized three or four times per year. Fertilizing requirements vary, depending on soil type. Soil tests and consultation with a local expert are recommended.