Phoenix, Sabal, Washingtonia and others
False Smut (fungus – Graphiola phoenicis): Small, black, wart-like bodies are seen (See Photo), often with yellow filaments protruding from the middle of the raised spots (See Photo). Both sides of the leaf are affected. A high incidence of the fungus on leaves can lead to premature death of older leaves. This is a common disease of date palms in south Texas, but chemical control is seldom required. Fungicides will protect against the disease.
Freeze injury: The loss of the outer trunk has been attributed to freeze injury (See Photo).
Leafspots (fungi – including Bipolaris spp., Exserohilum spp., Colletotrichum spp., Annellophora spp.): The spots are usually small, brown to black, and occur mainly on older leaves. Small, black fruiting bodies may be seen in dead tissue (See Photo). The presence of a few fungal leafspots does not usually indicate a serious disease problem. They may occur on tissue that has been weakened as a result of an environmental stress such as poor drainage. Alleviating the stress will end the problem. Chemical control is seldom required. Sometimes copper-containing fungicides can cause leafspots that resemble those caused by fungi (See Photo). Potassium deficiency can also cause leafspots (See Photo). Fungicides can be used to protect against leaf-infecting fungi when there is high disease pressure (i.e. sustained humid or wet conditions).
Lethal Yellowing Disease (mycoplasma): In the Rio Grande Valley, the Canary Island date palm (Phoenix canariensis) and the true date palm (Phoenix dactylifera) are affected, although other species of palms found in other areas are also susceptible. The disease is first noticed when lower leaves turn yellow (See Photo), then brown and droop (See Photo). The wilt spreads to upper leaves. As all the leaves collapse, the appearance resembles a “closed umbrella.” Eventually, all the dead leaves drop and only the trunk remains. This process takes about 4 months following observation of initial symptoms. The disease has been controlled in other areas by repeated injections into the trunk with an antibiotic (oxytetracycline). However, the treatment is not a cure; it only alleviates symptoms and must be repeated every three to four months. Species adapted to Texas that are resistant include: Mexican fan palm (Washingtonia robusta), California fan palm (Washingtonia filifera), pygmy date palm (Phoenix roebelenii), Texas palm (Sabal texana), and Queen palm (Syagrus romanzoffiana).
Rachis Blight (fungus – Serenomyces californica): This disease has been found on the California fan palm (Washingtonia filifera). Portions of the rachis, running longitudinally, have a brown discoloration (See Photo). The inside of the rachis is also discolored. As the disease progresses, fruiting bodies of the fungus are formed within the rachis. As they mature, the rachis surface is broken, revealing masses of dry, rust-colored spores (See Photo). Distinct portions of the leaf are killed; the dead area is associated with where its vascular system originates from the diseased area of the rachis (See Photo). There is no treatment known, although removal of infected foliage may prevent spread to other foliage.
Fungicides for Palm
- Copper oxychloride
- Copper sulfate (basic)
- Copper sulfate
- Copper sulfate (basic)
- Copper hydroxide
- Kocide 101
- Kocide DF
- Washingtonia palm (Washingtonia robusta): Pestalotia leaf spot
- Queen palm (Syagrus romanzoffiana): Exosporium leaf spot
- C.O.C. WP (86.2%)
Copper sulfate (basic)
- CP-Basic Copper TS-53% WP
- Cuproxat F 27.1