Why Are My Robellini Leaves Rusty?

Pygmy Habitats

• Phoenix roebelenii originated in humid river bed regions of south China, Laos, Myanmar and Vietnam. As a landscape specimen this short tree grows best in U.S. Department of Agriculture plant hardiness zones 10 and 11, although sheltered plants can survive in USDA zone 9. It's often used as a houseplant or as a container plant kept outside in temperate regions during the summer and moved inside when frosts threaten. In its natural habitat, pygmy date palms sucker -- but that characteristic has disappeared in domestic plants. Place pygmy date palms in full sun in humid areas and in filtered light or partial sun in desert gardens.

An Ounce of Prevention

• Proper care of your pygmy date palm reduces the incidence of diseases and pests. The plants are not drought tolerant but should be watered in early morning before sunlight reaches the leaves. To avoid fungi and rot problems, do not water in the evening because moisture might remain on the leaves overnight. Most diseases that affect pygmy palms involve fungi and rot, and result from improper watering and irrigation. Some diseases result from deficiencies in micronutrients, especially manganese, magnesium, nitrogen and potassium. Scales and spider mites are frequent problems on houseplants, but outside plants are typically pest free.

Focusing on Fungus

• The majority of rust-colored leaf spots on pygmy date palms result from fungi caused by poor water management and improper cleaning of dead leaves. Both set up conditions for the growth of spores and fungus. While there are many, the most common are pestalotiopsis and pestalotia. If you ignore the fungus and don't address the palm's environmental conditions, it can lead to a condition known as fatal bud rot.

Rusty Spots

• Small reddish brown rings surrounded by halos of contrasting colors on pygmy date palm leaves suggest leaf spots, a symptom for concern. The rings represent diseased tissue caused by numerous sources. Both potassium and manganese deficiency have early symptoms that include leaf spots. The exact cause of fungal leaf spots requires identification of the spores. Fortunately water management, plant sanitation, preventing injuries and palm nutrition can help prevent further spread of the disease.

Actual Rust

• Rust, the fungus and not the by-product of metallic oxidation, can appear on stems of pygmy palm trees as well as other palms. This is also caused by fungi and displays as yellow or orange spots on the leaves and the trunk. They’re not considered serious other than as a cosmetic concern.