Pygmy date palms (Phoenix roebelinii) are small palms that are used in containers or outside landscapes. They grow slowly, reaching an average height of 6 to 8 feet. Pygmy date palms have dense, arching crowns and work well as specimen or accent plants.
Leaf Spots and Blights
Pygmy date palms are susceptible to leaf spots and blights caused by fungi and bacteria. Affected areas begin as small water-soaked lesions, which turn brown, reddish-brown, yellow, gray or black. The lesions may be surrounded by a ring or halo. Leaf spots refer to areas that remain separated, while leaf blights refer to areas that merge together. Leaf spots and blights affect leaves of all ages. With optimum conditions, they may eventually affect entire leaves or leaflets, which dry out and die.
Remove and dispose of infected leaves. A fungicide approved for leaf spots and blights on pygmy date palms applied at the manufacturer's recommended rate may prevent the spread of the disease, but will not cure the infected leaves.
Petiole and Rachis Blight
A petiole is a stalk or stem that connects a leaf to a leaf base on the trunk of a plant. A rachis is the part of a petiole that extends into the leaf blade of a palm. Petiole and rachis blights are caused by a fungus on the petioles and/or rachises of the oldest (lowest) leaves of Pygmy Date Palms. The fungus does not infect the leaves.
Long brown or reddish-brown lesions appear on infected petioles and rachises. The fungus destroys the channels that carry food and water to the leaf, causing one side of the leaf to die. A cross-section of an infected petiole or rachis will have discolored plant tissue.
Petiole and rachis blights weaken Pygmy Date Palms, but will not kill the tree. Prune and destroy infected plant parts. A fungicide approved for petiole and rachis blights on Pygmy Date Palms used according the manufacturer's directions may prevent the spread of the disease. The fungicide will not cure the affected plant parts.
Fungal and bacterial infections can cause bud rot at the top of the trunk of pygmy date palms. The first sign is the discoloration and wilting of the spear leaf (first leaf) and the next youngest leaf. When the tree's canopy is above eye level, the first noticeable symptom may be the lack of new leaves or an open crown.
As the disease develops, the spear leaf can be pulled out of the bud easily. Its base will be rotten and have a bad odor. Older leaves may remain on the trunk for many months before being affected.
A laboratory analysis can determine if the bud rot is caused by a fungus or bacteria. Fungal rot usually occurs during the rainy season, especially after a tropical storm or hurricane. It is fatal, so remove and destroy the infected plant. If the plant is in a container, dispose of the potting mix also. A fungicide approved for bud rot on palms may be applied according the manufacturer's directions to nearby palms as a preventative measure.
Bacterial rot is caused by cold damage and the tree may recover. The first leaves to appear after the infection will be abnormally short. Each successive set of leaves will be slightly longer until the canopy is normal size. If the tree does not appear to be recovering, remove and destroy it.
Ganoderma Butt Rot
There are no preventative or curative measures for butt rot caused by ganoderma fungus. Butt Rot destroys the internal wood of the trunk, which results in wilting, slow growth and off-color foliage.
A half-moon-shaped soft mass may form a shelf-like structure on the lower 4 to 5 feet of the tree. This mass is called a conk and hardens with age. It is the result of the fungus growing out of the trunk and does not appear on all infected trees. The affected tree, its stump and complete root system should be removed. Another palm should not be planted where the affected tree was located, since the fungus can live for years in the soil.
Proper care of pygmy date palms can reduce the incidence of diseases. They should be planted in partial shade to full sun with regular irrigation. Palms are not drought tolerant. They should be irrigated in the pre-dawn hours so the leaves can dry quickly and overhead irrigation should not be used.
Palm fertilizer should be applied at the rate recommended by the manufacturer. The fertilizer should include micro-nutrients needed by palms, especially magnesium and manganese. Other micro-nutrients used by palms include boron, copper, iron, sulphur and zinc.