The fatal disease of palms known as Texas Phoenix palm decline — or TPPD — was positively confirmed in Louisiana last month, according to LSU AgCenter plant doctor Raj Singh.
The disease was confirmed in Canary Island date palm trees in New Orleans, Singh said. Until recently, the disease was only detected in the United States in Texas and Florida, he added.
TPPD is a progressive disease that rapidly kills various types of palm trees, including Canary Island date palm, edible date palm, silver date palm, wild date palm, cabbage palm and queen palm, he said.
“Trees that appeared healthy this time last year are now dead, and we are talking about almost 100 year old trees…it’s pretty quick- acting,” LSU AgCenter horticulturist Andrew Loyd said.
Details surrounding the question of how TPPD ended up in Louisiana and its origin are still unknown, Singh said.
“The disease could be present in other parts of the state, but we would have to go and survey the whole state and see if symptoms are present and confirm it,” he said.
Singh said as of now, only two Canary Island date palms have tested positive for the disease in New Orleans.
TPPD is caused by a Phytoplasma called Candidatus Phytoplasma palmae, an unculturable bacterium with no cell wall , though phytoplasma is transmitted by phloem (vascular channels that transport photosynthates) feeder insects with piercing-sucking mouth parts, he said.
Singh said the exact species of the insect vector is not confirmed yet, but insects such as tree hoppers, plant hoppers and psyllids are the potential vectors of this disease.
These insects pick up the phytoplasma while feeding on infected palms, and then transfer it to healthy susceptible palms, he explained.
Once introduced, the phytoplasma colonizes in the phloem channels and becomes systemic in the host, he said. However, the phytoplasma can’t live outside the host or the insect, he added.
“One doctor said finding the infected trees is like putting on a blindfold and looking for one white marble in 100 red marbles,” Loyd said.
The progressive symptoms of TPPD include the discoloration or browning of fronds in the lower canopy. The lower leaves will quickly turn brown, and the flowers, if produced, will die and fall off the tree prematurely. Once the spear leaf dies, the entire palm tree is dead, Loyd explained.
Singh said symptoms of TPPD are similar to those of other diseases, thus making it more difficult to positively identify the disease.
Additionally, he said self- diagnosis of the TPPD is almost impossible, given the need to confirm the disease by molecular detection of the pathogen from symptomatic tissue.
Infected or symptomatic palms, especially where the spear leaf has died, must be removed immediately because they may act as a source for insects to transmit the pathogen to healthy susceptible palms, Loyd said.
“The two diseased palms have not been removed, but I think one is in the process,” Singh said. “There are several palms showing symptoms in the same area.”
Singh doesn’t recommend replacing another palm in the same location as a diseased palm, unless the palm is different than one of the six susceptible palms.
Anyone who believes their trees might be infected by TPPD can send samples into the LSU AgCenter Plant Diagnostic Center for positive identification. However, individuals are encouraged to call the AgCenter before collecting any samples, Singh said.