(02/21/18) BATON ROUGE, La. — Date palm lethal decline, also known as Texas Phoenix palm decline, is a deadly disease that can rapidly kill mature tall palm trees.

The disease was first confirmed in New Orleans in December 2013 in several Canary Island date palm trees, said LSU AgCenter “Plant Doctor” plant pathologist Raj Singh. In subsequent years, the disease was detected in medjool date palm trees and sabal palm trees in Jefferson, Orleans and St. Bernard parishes.

“Last fall, several Chinese windmill palms (Trachycarpus fortunei) exhibited typical symptoms associated with date palm lethal decline,” Singh said. Symptoms include a large proportion of discolored leaves in the lower region of the canopy, dead spear leaves and rapid death of palm trees.

“Affected palms tested positive for date palm lethal decline,” Singh said.

The pathogen has been known to cause decline in Canary Island date palms (P. canariensis), edible or medjool date palms (P. dactylifera), pigmy date palms (P. roebelenii), silver date palms (P. sylvestris), wild date palms (P. reclinata), cabbage palms (Sabal palmetto) and queen palms (Syagrus romanzoffiana).

The scientific names of the various palm trees are important so people know which palm trees are reported as hosts of this disease, Singh said.

“The disease is caused by a phytoplasma, CandidatusPhytoplasma palmae, an unculturable bacterium with no cell wall,” he said.

The pathogen colonizes in the phloem food conducting tissue from where it spreads systemically to new plant parts. Scientists suspect the pathogen is moved by sap-feeding insects with piercing-sucking mouthparts, such as plant hoppers, psyllids or tree hoppers, although the exact species of the insect vector is not known, he said.

“Management of date palm lethal decline in infected palms is not possible,” Singh said.

A palm demonstrating symptoms of a dead spear leaf must be removed immediately, as it may serve as a source of the pathogen for the insect vectors to transmit to healthy susceptible palm trees, he said.

“Successful disease management in a landscape where date palm decline is prevalent can be achieved by preventative treatment of healthy susceptible palm trees with the antibiotic oxytetracycline hydrochloride,” he said. The antibiotic should be administered as a trunk injection every three to four months.

Accurate identification of date palm lethal decline is required for effective disease management. “Other diseases and disorders of palms may produce similar symptoms, which can make it hard to identify the disease based solely on symptoms,” Singh said.

Molecular detection of the pathogen from symptomatic tissue is required for positive confirmation. “Samples from suspected palms can be submitted to the LSU AgCenter Plant Diagnostic Center for positive identification, but before you collect any samples, please contact us,” Singh said.

Singh can be reached by calling at 225-578-4562 or emailing rsingh@agcenter.lsu.edu.

Date palm lethal decline caused the death of a mature Chinese windmill palm tree. Photo by Raj Singh/LSU AgCenter

Chinese windmill palm tree exhibits brown discoloration in lower canopy. Photo by Raj Singh/LSU AgCenter