Symptoms
It has been observed to almost exclusively attack the Canary Island palm, but is seen on other species. Since 2009, Texas Phoenix palm disease is known to severely affect the ''Phoenix spp.'' and ''Sabal spp.'' palm trees: Canary Island date palm, silver or sylvester date palm, Queen palm, Sabal palm, and cabbage palm. All of these trees have been observed to have the same symptoms. The complete host range of this phytoplasma strain is not known.Broschat, Timothy K., Monica L. Elliot, and Ian Maguire. "Texas Phoenix Palm Decline." A Resource for Pests and Diseases of Cultivated Palms. University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS), and the Center for Plant Health Science and Technology (USDA/APHIS/PPQ/CPHST), 1 2010. Web. 23 Oct 2012. http://itp.lucidcentral.org/id/palms/symptoms/Texas_Phoenix_Palm_Decline.htm If the palm tree is mature enough to produce fruit, it will experience two major symptoms. Premature drop of the majority or all of the fruit, within a short time period (about three days), is an obvious symptom. Soon after this, the flowers become necrotic. However, these symptoms can only be observed during flowering and fruiting season, and if the flowers have not been trimmed from the tree. At any palm age, early infection will show discoloration of theDiagnostics
A large issue with controlling this disease is that it is difficult to diagnose. The early symptoms may appear to be the cause of 'over-trimming' of the leaves or nutrient deficiency. The progression of the symptoms is from the inside of the tree, out and are not immediate."Disease Attacking Florida's State Tree." Bartlett Tree Experts (2009): 20. American Forests. Web. 1 Dec. 2012. The death of the spear leaf indicates the death of the apical meristem, which is diagnostic for a phytoplasma infection. Since phytoplasmas are not culturable, a molecular test can be done to confirm its presence. A sample must be sent to a local extension office for testing. To acquire a sample, boring into the trunk must be done with a drill. It is not known how soon the TPPD phytoplasma can be detected from this test, but it is generally not seen in plants without symptoms. Other times, it is not detectable until the spear leaf dies.Disease cycle
The specific disease cycle for TPPD is not known, since the vector is unidentified. Planthoppers, psyllids, or treehoppers are the suspected carriers. For this reason, a general disease cycle of mollicutes by related insect vectors is described as the cycle for TPPD. Phytoplasmas colonize in the phloem tissue of their hosts. This allows the pathogen to spread systemically through the vascular system into new leaves of the plant.Agrios, George N. Plant Pathology. 5. London: Elsevier Academic Press, 2005. 689-690. Print. Since phytoplasmas are not known to survive without their host (plant or insect), the process of the overwintering (unfavorable conditions) stage is unknown. The exact spot in the cycle where the spear leaf dies is not absolute, but it is thought to be early in the disease process. When a healthy insect vector feeds by piercing the vein of a leaf and sucking the phloem sap, the pathogen is ingested into the gut of the insect. Before the infection can be spread from plant to plant, an incubation period is needed for distribution throughout the insect. Once the phytoplasma is ingested from the plant, it multiplies in the gut of the insect, travels into the hemolymph, then to the salivary glands. Here, in high enough concentrations, the phytoplasma is transmitted into new plants when the insect feeds.Environment
The only area this disease in known to infect is the southern coastal regions of Texas and Florida. It is not known how the phytoplasma reached Florida, but it is likely it was brought over from an unknown insect vector since movement of palms from the Texas coast to Florida is not routine. It is not known whether this phytoplasma prefers the climate of these coastal regions or a specific host. As of now, the only hosts known to carry this disease are a range of palm species. To favor development, the area of infection must have a high population of insect vectors (planthoppers, psyllids, or treehoppers) for continuous, successfulManagement
There are two main methods of control for Texas Phoenix palm decline: Removal of dead spear leaves of the palm tree and the application of an antibiotic called oxytetracycline HCl (OTC). If the spear leaf dies, there are healthy leaves beneath them, and the control method of implementing the removal of dead spear leaves is to be used. Unless the removal of these dead spear leaves occurs, this gives a chance for the vector to use these diseased spear leaves and transmit the disease to other nearby susceptible palm trees. If the spear leaf has not yet been killed by TPPD, antibiotics are added to afflicted palm trees by injecting it into the trunk of the tree. These applications have a liquid composition. They are applied either when the plant is expressing symptoms of TPPD or as a source of protecting known susceptible palm species from ever acquiring the disease. This antibiotic cannot be used on just any palm species. It should rather be used only on prone species palm to TPPD. Over the course of four months these antibiotics will be integrated, if used. Future implications that have not been stable in terms of success or effectiveness, but that still hold promise are discovery of resistant strains of palm or control of vector population. These are not used however due to not knowing the complete known palms TPPD effects and the vector not being totally known either.Importance
Texas Phoenix palm decline is classified as a systemic disease and it is known to rapidly kill its hosts. Although it is dispersed around by vectors, at this time it is still unknown as to which what specific vectors exactly are carrying and spreading this disease. The palm disease TPPD has no known cure. In response to the disease outbreak inReferences
{{reflist, 30em Tropical agriculture Palm diseases