Looking Out for Palm Diseases 

Caring for palms can be a daunting task. Being a major feature in many landscapes, issues can become highly noticeable. Before we get into what to look out for related to diseases, let’s talk about fertilizer. Most palms in out landscapes are not native and out native soils do not have the nutrients needed to keep them in good health. This results in a need to regularly fertilize. Research conducted by the university of Florida shows that a palm fertilizer with 8-2-12 +4 provides the best nutrition for our palms. The extra magnesium in this formula is vital for optimal palm health. Palms must be fertilized on a schedule to keep them healthy. Once you start to notice nutrient issues in the palm leaves, the palm is significantly deficient. Correcting this takes time.

Fertilize your palm on a schedule 4 times a year in February, May, August and November. Be sure to read the package and apply the correct rate of fertilizer. Applying too little can lead to nutrient deficiencies and applying too much can lead to nutrient toxicity and/or runoff that can lead to algal blooms in our water bodies. Why is fertilizing so important? Many diseases can start off looking like a nutrient deficiency. If you are already fertilizing regularly and correctly, we can rule out a nutrient issue and go straight to disease symptoms to determine what is wrong with your palm. In my driving around town, there are a LOT of nutrient deficient palms. Let’s work on fixing that!

Now that your palms are healthy, se can start to talk about diseases, well, almost. One more palm maintenance tip. Do not prune off leaves until they are completely dead. There are two reasons for this. One is that the palm is reabsorbing the nutrients form the lower leaves. You likely paid for those nutrients, so save some money and let the plant hang on to the nutrients and use them for new leave. Next, if you palm does have a disease, anyone working to diagnose the issue need to see the leaves in the process of decline. If you remove the leave, it will take longer for us to determine what is going on.

Now for what you have been waiting for, palm diseases! They really are not something to get excited about, but they are important to know about and know what to look for. Remember to always sanitize tools between plants to limit potential spread.

• Phytophthora Bud Rot (Pytphthora palmivora) is a fugal disease that is long lived in soils. Do not plant another palm in the same location if you lose a palm to this disease. Wilting and discoloration in the center spear is an indicator. It will first turn yellow, then brown while the older leaves remain green. Unfortunate, there is no cure for this disease. Infected palms require removal and incineration.

• Thielaviopsis Trunk Rot (Thielaviopsis paradoxa) is another fungal disease. Leaves will and die. You may see stem weeping on the trunk. Spores remain in the soil as the disease above. Do not plant a new palm in the same location if you lose a palm to this disease. There is not prevention, nor cure. Remove and incinerate diseased palms.

• Ganoderma Butt Rot (Ganoderma zonatum) is yet another fungal disease. This one impacts the lower 4-5 feet of a palm trunk. This fatal disease can show up as leaf wilting and discoloration. You may also see fungal conks growing out of the trunk. Remove and incinerate the palm. Do not replant a palm in that location.

• Fusarium Wilt (Fusarium oxysporum f. sp Palmarum) is a fungal disease the impact Queen, Mule and Washentonian palms. This disease hits fast and gives a freeze dried appearance. The palm leaves die, but stay uprights. A sign of a declining palm is one side of the leave dying while the other side remains green. There is no cure, and infected palms must be removed.

• Rachis  blight (Diplodia spp.) is the only palm disease on this list that rarely kills a palm. Another fungal pathogen, it presents similar to Fusarium Wilt. Diagnostics testing is required to determine which disease is present. While there is no cure, foliar fungicide applications reduce the spread on new leaves. Remove infected leaves promptly.

• Lethal Bronzing is caused by a plasmodium bacterium. There are at least 16 different that can be infected with this disease. It takes 4-5 months from infections to see symptoms. It takes 2-3 months form the first symptom to the death of the palm. You can treat palms with a preventative by inject ions of oxytetracyline HCI (OTC) every 3-4 months. For at least 2 years. If the disease has reduced in the area after 2 years, you may be able to stop the treatments. If not, keep the treatments going. Trunk core sampling can be done to test for the disease. Once the palm as symptoms, it will die. The main benefit to testing is to confirm the diagnosis, to that other trees in the area can be protected with the inoculation, if the homeowner chooses. Remove promptly to reduce spread.

If you think your palm ask a disease you can contact your local arborist or landscape palm expert to have an inspection. Contact your local extension office for additional assistance       .

Helpful Palm Resources: 

https://flrec.ifas.ufl.edu/palmprodpalm-problems-key/palm-problem-keys/palm-problem-key—leaves/

https://gardeningsolutions.ifas.ufl.edu/care/pests-and-diseases/diseases/lethal-bronzing-disease/

https://edis.ifas.ufl.edu/publication/IN1240

https://edis.ifas.ufl.edu/topics/palms

https://edis.ifas.ufl.edu/publication/EP344

https://flrec.ifas.ufl.edu/palmprodpalm-problems-key/

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