Palm Diseases and Nutritional Problems

Palm trees may appear carefree, but they are susceptible to various diseases, insects, and nutritional deficiencies. By following recommended practices, you can help keep your palms healthy and vibrant. In this article, we will explore common palm diseases and nutritional problems and discuss prevention and treatment methods.

Diseases

Leaf Spots

Palms are often affected by leaf-spotting fungi. These fungi cause circular or elongated brown spots on the leaves, which may appear oily. Differentiating between these fungi based on visual symptoms alone is challenging.

Prevention & Treatment: Avoid wetting the foliage during irrigation to prevent leaf spots. In most cases, leaf spots alone won’t kill the tree, and fungicides are usually unnecessary. However, severe cases may require fungicidal sprays containing copper. Make sure to follow the instructions on the label for proper application.

False Smut

False smut, also known as Graphiola leaf spot, is caused by Graphiola species. This disease is prevalent in areas with high humidity and affects palms in the Arecaceae family. Commonly affected palms include sabal palmetto, jelly or pindo palm, Chinese fan palm, and Washington palm.

Infected leaves exhibit small black wart-like structures on both surfaces, with tiny filaments sometimes emerging. Young leaves typically show no symptoms.

Prevention & Treatment: To reduce humidity, ensure proper spacing between palms for adequate air circulation. Avoid wetting the fronds during irrigation. Removing severely infected fronds can help minimize disease spread, but be cautious not to remove too many, as it can weaken the tree. Fungicides containing copper can be used preventatively in the spring. Follow the instructions on the label for application rates and intervals.

Ganoderma Root & Butt Rot

Ganoderma root and butt rot is caused by the fungus Ganoderma zonatum and affects various palm species. Symptoms include withering and drooping of older fronds, stunted growth, and pale green or yellow new growth. Infected palms may develop a hollow sound when tapped and exhibit dark brown tissue when dissected.

Prevention & Treatment: Remove and destroy any dead palm root systems, stumps, or trunks from the landscape, as the fungus survives on plant tissue. Avoid tree injuries during planting, staking, and maintenance. Since Ganoderma persists in the soil, it’s not advisable to plant another palm in the same location. Unfortunately, there are no chemical controls available for this disease.

Bud Rot

Bud rot can be caused by various fungal or bacterial pathogens. Symptoms include black lesions on buds and young fronds, wilting of young leaves, and rotting of the bud. Eventually, only the trunk remains.

Prevention & Treatment: Minimize overhead irrigation to prevent infection. Once bud rot occurs, plant recovery is unlikely. Infected palms should be promptly removed and destroyed to prevent further spread. Preventative fungicides containing copper can be applied to plants exposed to the disease. Follow the instructions on the label for application rates and intervals.

Nutritional Problems

Palms often suffer from inadequate mineral nutrition, with the most common deficiencies being nitrogen (N), potassium (K), magnesium (Mg), and manganese (Mn). Boron (B), calcium (Ca), copper (Cu), and zinc (Zn) deficiencies are less common.

Nutrient deficiencies can arise from insufficient nutrients in the soil, nutrient imbalances, poor soil aeration, high soil pH, or excessive planting depth.

Potassium (K) Deficiency

Potassium deficiency is a widespread and severe disorder in coastal South Carolina. Symptoms first appear on the oldest leaves and progress to newer leaves. The leaves develop translucent yellow to orange spots, necrotic spotting, and withered tips. Eventually, the leaves can become burnt and frizzled, and the deficiency may be fatal to the palm.

Prevention & Treatment: Prevent and treat potassium deficiency by using slow-release potassium sulfate fertilizers. Simultaneously applying slow-release magnesium prevents a potassium to magnesium imbalance. Although damaged leaves won’t recover, new growth should become healthy and replace the injured leaves.

Manganese (Mn) Deficiency

Manganese deficiency can be fatal to palms, especially in high pH soils. Symptoms include chlorosis between the veins, necrotic streaking on the newest leaves, frizzled and withered leaves, and reduced leaf size. Sandy soils tend to leach manganese more rapidly.

Prevention & Treatment: Have a soil test to determine soil pH, adjust it downward if necessary to increase manganese availability. Apply manganese sulfate to the soil around the palm two or three times per year. Ensure you follow the recommended rates and intervals mentioned on the product label.

Other Nutritional Deficiencies

Iron (Fe), nitrogen (N), magnesium (Mg), and boron (B) deficiencies are less common in palms but can still occur under specific conditions. Symptoms include chlorosis, tip necrosis, reduced growth, and abnormal leaf appearance.

Prevention & Treatment: Treat deficiencies with specific fertilizers containing the deficient nutrient. Adjust soil pH if necessary and follow fertilizer application rates provided on the packaging.

General Fertilizer Recommendations

To prevent nutritional deficiencies, implement a yearly fertilization program for mature palms in the landscape. Use a granular fertilizer formulated specifically for palms, often referred to as a “palm special.”

Apply palm fertilizer three to four times during the growing season (April to September) to ensure a consistent supply of nutrients. For mature palms, apply a slow-release fertilizer with an analysis of 8-2-12-4 (N-P-K-Mg). Make sure it contains trace nutrients. Fertilize the entire area beneath the palm canopy, as the roots can extend up to 30 to 50 feet from the trunk.

Adjust fertilizer rates for newly planted palms and avoid fertilizing them until after they produce new spears.

Consider using well-balanced palm fertilizers like PalmGain 8-2-12-4 Plus Minors or a slow-release fertilizer with a 12-4-8 analysis every two months during the growing season. Apply Epsom salts during the off-months between regular fertilization and use a product that provides the necessary micronutrients for palms.

Remember, once deficiency symptoms appear, it can take several months for the palm to recover.

By following these guidelines, you can maintain healthy and vibrant palm trees in your landscape.