Feature Article – for release week of August 24, 2008

Dan Culbert - Extension Horticulture Agent

 

 A New Threat to Paradise

Tropical Storm Faye has passed out of our area, bringing an end to our drought dangers, but leaving our Florida Yards a mess.  Many residents will be picking up the “leaves” from Florida’s state tree, the Cabbage Palm.  While cleaning up, take a careful look at the rest of the fronds on the palm, as a new disease of palms is threatening this symbol of paradise.  

Florida’s Cabbage Palm (Sabal palmetto) has been standing strong and tall for centuries.  The strength of the cabbage palm has been legendary—the palm-trunk walls of Fort Sullivan in Charleston protected soldiers from cannon-fire during a British invasion in 1776.  But cabbage palms in some areas of the state are dying. 

Palm specialists believe that the decline of cabbage palms is caused by the same microorganism that causes Texas Phoenix Palm Decline, a disease which has been recently confirmed in Sarasota, Manatee, Pinellas, Hillsborough and Polk Counties.  

Experts have determined that a type of bacterium, called a phytoplasma, is to blame. Now more than two hundred years later, researchers are searching for a way to help protect the palms.

Frequently Falling Fronds 

Recently cabbage palms affected by this disease have been found in some west Central Florida counties.  The symptoms include a “greater than normal” amount of dead fronds in the lower canopy.  A closer look at the central leaf spear under the “cabbage” also shows that it too is dead.  Eventually the disease will kill the entire palm.

Remember cabbage palms die or appear unhealthy from a variety of problems: lightning, nutrient deficiencies, over-trimming, deep planting, insects, other diseases, herbicides (roadside vegetation management) and fires (natural or prescribed burns).  Only palms with the symptoms described below should be suspected as being infected by this new pathogen.

Keep your eyes open

The disease can be difficult to identify, since over-trimmed and improperly fertilized palms in the landscape show similar but unrelated symptoms of this disease.  Be on the lookout for these symptoms on cabbage palms: 

• a greater than 50% discoloration of all fronds
• a brown spear leaf or dead apical meristem (bud).  

At this time the primary palm hosts of this disease are the Canary Island Date Palm (Phoenix canariensis), the Edible Date palm (P. dactylifera) and Wild Date Palm (P. sylvestris).  What is alarming is that Cabbage Palms and Queen Palms (Syagrus romanozoffiana) have also been affected by this disease.

Positive identification of TPPD is made by taking cores of palm trunk tissue and submitting them to a Plant Pathologist. Photo: Don Rainey, UF/IFAS Sarasota Extension

If you think the symptoms match what has been described here, please contact our Extension office.  Sending a photo with an email would be helpful.  We will visit the site and take a sample for laboratory analysis. There is a detailed sampling procedure that must be followed in order that a valid identification can be made.  

 

Since movement of palms occurs widely in Florida, it will not be surprising if people help to spread the disease, unknowingly, by moving the insect vector or infected palms.  While Date palms are grown in nurseries, Cabbage Palms are dug as full sized mature trees, and are stripped of their fronds to insure successful transplanting.  If someone removes these dying or dead leaves, this symptom may not be obvious. 

 

If you are planning to plant or have recently bought Cabbage or Date Palms, ask the nursery to identify exactly where they are coming from.  How far and how quickly Texas Phoenix Palm Decline will spread (both north, south and inland) is unknown.  Until we know more about the spread of this disease, be very cautious about purchasing these palms that have come from areas known to have this disease.

Looking for that ounce of Prevention

Resist the urge to cut down a tree just because it may become sick. However, once the disease is positively identified due to this disease, it should be removed immediately.

At this time there is a lot we don’t know about this disease.  Lethal Yellowing, a similar palm disease that affects mostly Coconut Palms, has been shown to be spread by a sap-feeding insect. The disease affecting Sabal Palms is also spread by an insect but the particular culprit in this case has not been identified yet. The use of insecticidal sprays is not being  recommended in the landscape right now, as there has been no evidence that insecticides were useful for controlling the disease on coconut palms.

If it is determined that palms in our area are affected by this disease, an injection of oxytetracycline hydrochloride (OTC) can be used to resist this pathogen.  Available in Florida as an EPA-registered product, TreeSaver® (http://www.palmtreesaver.com) has been known to help control other palm phytoplasma diseases. The antibiotic is best injected by a professional Arborist or landscape professional, typically three times per year.

Management options for palms in your Florida Yard (removal of infected palms and inoculation of nearby susceptible palms three times per year with OTC antibiotic) are geared to suppress the spread of the disease. There will be few, if any, management options for native palms in natural areas, especially without more knowledge of how this disease spreads.

 

I’ve placed pictures and more information on our award-winning Okeechobee web page, http://okeechobee.ifas.ufl.edu. If you need additional information on this dreaded Texas Phoenix Palm Decline, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 3 PM on Tuesday afternoons.  Go Gators! 

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Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean. Last update: 08/20/2008.  This page is maintained by Dan Culbert