Phoenix roebelenii, the pygmy date palm, is a small palm tree with a slender trunk and graceful arched branches. Despite the large spines at the base of each leaf, the tree is widely used in landscaping in frost-free areas. There are several diseases that affect the roebelenii including Texas Phoenix palm decline, bud rot, palm leaf skeletonizer and pestalotiopsis.
Texas Phoenix Palm Decline
Texas Phoenix palm decline is a fatal disease that quickly kills the roebelenii palm. It is caused by a bacterium that, as of 2010, has not been cultured in a laboratory, making it difficult to study. The earliest symptom is premature fruit drop; however, flowers are often trimmed off in landscape palms so no fruits develop. In landscape palms, the lower leaves begin to turn brown and die at a higher than normal rate. Then the spear leaf (newest leaf) turns brown and dies. After the death of the spear leaf, all leaves in the canopy die rapidly. When two-thirds of the leaves are dead, the roots weaken and the palm can be rocked. This distinguishes TPPD from lethal yellowing disease. Once TPPD is diagnosed, remove and destroy the tree to prevent further spread of the disease.
Bud rot is associated with both fungus and bacteria in roebelenii palms in Florida, according to the University of Florida Extension Service. The fungal disease can be treated with fungicides in a palm nursery; however, treatment of mature landscape trees is usually not effective. The first symptom of bud rot will be the death of the leaf spear, or the newest leaf in the canopy. No new leaves will emerge after the death of the leaf spear. The canopy will turn brown from the top (newest leaves) down. Remove or destroy diseased trees to prevent spread of the bacteria or fungus.
Palm Leaf Skeletonizer
A small white moth, Homaledra sabalella, is a major pest that attacks roebelenii palms. The moth lays eggs on the new leaves. When the caterpillars emerge, they feed on the leaves, form pupae and emerge as adult moths. As many as 100 larvae may attack a single leaf and consume most of the tissue, rendering it a skeleton. The infestation is not usually fatal. Remove and destroy infested leaves to prevent further spread of the pest.
Pestalotiopsis is a fungus that attacks many palms including the roebelenii palm. In most cases, the disease enters through a wound to the plant, such as the wound left when a green frond is pruned off. The first symptoms appear as yellow, brown or black spots on the leaves and stems. The spots grow and turn grey with black outlines. In mature landscaping plants, it is not necessary to treat this disease, as it often affects only a single leaf. Removing the diseased leaf may provide an opening for further spread of the fungus.