Lemon trees typically grow in warm climates and belong to the citrus family. Lemons are considered a part of the berry family. Lemons were brought to America by Europeans; the lemon was thought to originate in India and migrated to the Mediterranean region. Today lemons are found mainly in hot humid climates such as Florida and California although they can be grown elsewhere in the right conditions.
Most invasive insects that attack lemon trees appear as small discolorations on various parts of the tree; many of the pests can be found on leaves and bark. Aphids secrete honeydew; finding honeydew dripping from leaves is an indication of aphids present. The whitefly is a 1/12-inch long insect with white wings; these are found on the underside of leaves. Mites are the smallest insects being only 1/50-inch long and appear as tiny red or purple bumps on leaves. Snails can leave fruit scarred or pitted where they chewed into it. Silver gray colored curled leaves can be proof of citrus thirps which are tiny orange or yellow insects.
Various symptoms of citrus tree diseases can be attributed to insects found on lemon trees. Leaves showing holes or shriveling and discoloration is a sign of possible pest problem. Splitting bark, scale growth and lesions are signs of damage elsewhere on the tree. Severe signs or symptoms of prolonged infestation include defoliation and leaf drop. New growth that is curled, blistered or stunted also are signs of insect problems. Affected trees are slow to grow and may produce stunted or deformed fruit. Sooty mold on fruit and trees is a sign of aphids and scale bugs.
While the initial impact on the health of an affected tree may not be significant, ongoing health is greatly affected. Insects also allow or introduce bacteria and pathogens that can cause various other citrus tree diseases such as citrus canker and sooty mold. Other invasive insects, such as ants, can invade the tree when honeydew is present. Fruit and new growth are the most affected parts of a lemon tree when infested with bugs.
Treatment can involve chemical and natural remedies. Pesticides can be used to stop insects but also have detrimental impact on beneficial insects such as ladybugs and bees. Natural methods include removing pests with tweezers, insecticidal soap and water. Sufficient cleaning of the leaf surfaces will be needed to avoid leaf burn.
A common prevention is to keep the base of the trunk clear of any debris or overgrowth. This takes away places to hide or to lay eggs. Scheduled sprays and treatments will help keep invasive insects away from lemon trees. Lemon trees should also be well irrigated and fertilized to keep them strong enough to fend off insects.
Texas A&M University
University of Florida