Palm trees such as Mediterranean fan palm (Chamaerops humilis), date palm (Phoenix dactylifera) and California fan palm (Washingtonia filifera) grow in U.S. Department of Agriculture plant hardiness zones 8 through 11. In the United States, they are found in Florida and California. Many palm pest organisms are found only in the southern climates, but some pests feed off of northern growing palm trees as well.
Beetles and Weevils
The giant palm borer is a brown or black beetle that lives in the trunks of the palm tree. They tunnel into the wood leaving holes in the trunk. The larva feed on the inner parts of the tree, causing fronds to yellow and drop and the trunk to decay, eventually killing the tree. The red palm weevil has spread to the U.S. from Asia. The red weevils act similarly to the palm borers, killing a tree within a year after infestation. Destroy infected trees, and keep palms healthy so they are least susceptible to the pests.
Soft and Armored Scale
Scales are tiny insects that look like bumps on a plant's surface. Armored scales have a hard outer shell that covers the insect while it sucks fluids from the palm tree. Soft scales do not have armor, and they secrete honeydew as they feed on the tree. Scales will weaken the tree, but do not usually cause permanent damage to palms. Prune infested fronds. Place sticky tape around the bottom of the tree to keep ants from helping the scales against natural enemies such as ladybugs and parasitic wasps. Wash the scales from the tree, and spray with horticultural oil every seven days until the scales are gone.
Spider mites feed on palm trees year-round. Large numbers can damage trees. Eriophyid mites cause blisters on leaves but do little real damage. Check under yellowed fronds for the presence of mites. Ladybugs are natural predators that will help control the mites. Keeping the palm tree watered will make it less susceptible to damage. Prune off heavily infested fronds. Spray the tree with pressured water to dislodge the pests. Avoid using pesticides; use horticultural oil if a chemical treatment is necessary.
Caterpillars, Mealybugs and Whiteflies
Caterpillars create web shelters in the tree foliage. They feed on the fronds as they grow. Eventually the loss of foliage can weaken or kill the palm tree. Prune heavily infected fronds and scrape off any visible eggs. Apply Bacillus thuringiensis when the larva appear. Mealybugs are covered with a waxy, powdery substance. Whitefly eggs and larva are on the underside of fronds. Mealybugs and whiteflies cause fronds to yellow and drop as they feed on the plant liquids. They also excrete honeydew that leaves sticky, black mold. Prune infected fronds and dispose of them.
- Monrovia: Mediterranean Fan Palm
- University of California Integrated Pest Management: Scales
- University of California Integrated Pest Management: Giant Palm Borer - Dinapate Wrighti
- ANR News Blog: Another Palm Tree Infested with Red Palm Weevil
- University of California Integrated Pest Management: Spider Mites
- University of California Integrated Pest Management: Gall and Blister Mites
- University of California Integrated Pest Management: Whiteflies
- University of California Integrated Pest Management: Foliage-Feeding Caterpillars
- University of California Integrated Pest Management: Foliar-Feeding Mealybugs
- University of California Integrated Pest Management: Palm Disesases in the Landscape
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