Chinese fan palm (Livistona chinensis) is a showy evergreen that produces a dense canopy of bright-green, fan-shaped leaves and long flower inflorescences. The palm grows in U.S. Department of Agriculture plant hardiness zones 8 to 11. If your palm's leaves are turning brown, it may be from lethal yellowing disease, a fatal palm disease spread by plant-hopping insects. Lethal yellowing often starts in the middle of the canopy, where leaves begin to turn yellow. They then turn brown over a period of a few weeks.
1. Chemical Control
You can control lethal yellowing with the antibiotic oxytetracycline, which must be applied to the trunk via liquid injection approximately every four months. For best results, it must be injected as soon as symptoms appear, according to the American Phytopathological Society. Dosage depends on the size of the palm. This option may be cost prohibitive for some gardeners, because the palm must receive injections indefinitely -- antibiotics do not cure the disease, only keep symptoms at bay.
2. Possible Replacement
You may wish to replace your Chinese fan palm with a palm that's not susceptible to lethal yellowing, such as a cabbage palm (Sabal palmetto) or the royal palm (Roystonea regia). The cabbage palm is suitable for USDA zones 8 to 10, growing in full sunlight or partial shade and preferring a well-draining soil with average moisture. The royal palm grows best in USDA zones 9b to 11, requiring full sunlight and well-draining, moist soil.
If more than a quarter of the Chinese fan palm's foliage is discolored, the American Phytopathological Society recommends removing the palm from your landscape -- it's too far gone and unlikely to respond to antibiotics. Though the disease is spread by plant-hopping insects, insecticides are not generally considered effective at controlling them. If only the lower leaves are brown, these may simply be dead older leaves. This is natural and no cause for alarm.
4. The Palm's Culture
In USDA zone 8, the palm may survive temperatures as low as 15 degrees Fahrenheit, though the leaves may develop some frost damage. Where it's borderline hardy, plant the palm in a sheltered, south-facing location to protect foliage. The palm is not picky about soil and will grow best in bright sunlight, though young palms can benefit from partial shade. Water regularly to encourage healthy growth.