(10/05/17) Baton Rouge, La. — A deadly disease called lethal yellowing of palms has been positively confirmed on silver date palms and Chinese windmill palms in Baton Rouge, said LSU AgCenter plant doctor Raj Singh.
“In the United States, the disease has only been found in Florida,” Singh said.
A similar disease called date palm lethal decline, also known as Texas Phoenix palm decline, has previously been reported on Canary Island date palm trees in New Orleans during December 2013.
Lethal yellowing and date palm lethal decline are caused by two different strains of a phytoplasma. The lethal yellowing of palms strain is closely related, but genetically distinct from date palm lethal decline phytoplasma.
“It is a fatal disease that rapidly declines and kills the infected palms,” he said.
The pathogen is known to cause decline in more than 35 palm species. Some host palms found in Louisiana include Canary Island date palm, Chinese windmill palm, edible date palm, silver date palm and queen palm.
“A plant hopper is responsible for transmitting the pathogen into palms, where the pathogen colonizes systemically in the phloem tissue,” Singh said.
Symptoms of the disease in tall palms start with discoloration of older leaves. Then, the infected leaves turn reddish-brown to dark-brown, and they eventually die.
Palms infected with this disease exhibit a large proportion of discolored leaves in the lower region of the canopy.
Infection on palms that produce fruit leads to premature fruit drop and dead flowers.
“As the disease develops, the spear leaf dies after approximately one-third of the lower leaves have discolored, and diseased palms die rapidly within three to five months after the first appearance of symptoms,” he said.
A symptomatic palm with more than one-fourth of its foliage discolored in the canopy and a dead spear leaf must be removed immediately, as it may serve as a source of the pathogen for the plant hopper to transmit the disease to other palms.
Accurate identification of this disease in the field is required for effective disease management, Singh said.
Other diseases and disorders of palms may produce similar symptoms, which can make it hard to identify the disease based solely on symptoms.
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.
More information about lethal yellowing of palms can be obtained by calling Singh at 225-578-4562 or by email at firstname.lastname@example.org.
This silver palm is infected with lethal yellowing of palms disease. (Photo by Raj Singh, LSU AgCenter)
These dead Chinese windmill palms were infected with lethal yellowing and have a dead flag leaf. (Photo by Mary Helen Ferguson, LSU AgCenter)