Palms in Lethal

Texas works to contain lethal bronzing, prevent lethal yellowing from wiping out palm trees Palms in Lethal Decline

A DEADLY PLANT DISEASE that decimates palm trees has the entire state of Florida and parts of Texas under quarantine. Previously known as Texas Phoenix Palm Decline, lethal bronzing is caused by phytoplasma and primarily attacks date palms. But it can strike other species of palms, according to Kevin Ong, Ph.D., associate department head for extension programs in the Texas A&M University Department of Plant Pathology & Microbiology.

“Lethal bronzing may be a new name, but the disease is nothing new,” Dr. Ong says. “In the 1970s, a bunch of Canary Island palms died in Corpus Christi. We didn’t know what it was at the time but suspected it may have been lethal bronzing.”

As Dr. Ong explains, that event serves as an illustration of the impact lethal bronzing can have on the landscaping industry. Infected palm trees turn yellow, rot, and lose their leaves and fruit prior to maturation. Mature palms with the disease prematurely drop most or all of their fruits. The spear leaf dies relatively early in the disease development process. The flowers then die, followed by discoloration of foliage,

which begins at leaf tips. Leaves may briefly turn yellow and then transform into varying shades of reddish-brown to dark brown or gray. At this point, the plant can’t survive.

Under Quarantine Currently, Cameron, Hidalgo, Nueces, and Willacy counties, as well as parts of Kleberg and Harris counties are under quarantine to prevent lethal bronzing’s spread. Dr. Ong says how lethal bronzing spreads isn’t clearly understood.

“We have good guesses: It may spread through an insect vector known as the leafhopper. At this point, we have just circumstantial evidence,” he says.

The Texas Department of Agriculture (TDA) has guidance for shipping palms from quarantined areas of Texas when accompanied by TDA-issued phytosanitary certificate under these conditions:

•Quarantined palms located within 1 mile of a known infected tree may not move from the quarantined area for

a period of six months following removal of an infected tree. •Quarantined palms can move after six months if no other infected trees are found within a mile radius. Quarantined palms located more than 1 mile and less than 2 miles from known infected trees must be inspected within 24 hours prior to shipment with no symptoms of lethal decline apparent, and they must have been treated with a pesticide labeled by the Environmental Protection Agency (EPA) and approved by TDA, using the label directions for leafhopper control for a period of three months prior to shipment. In addition, they must be treated within 48 hours prior to movement. •Quarantined palms located more than 2 miles from known infected trees must be inspected within 24 hours prior to shipment with no symptoms of lethal decline apparent; treated with a pesticide labeled by EPA and approved by TDA, using the label directions for leafhopper control for a period of six weeks prior to shipment; and additionally treated within 48 hours prior to movement. •The tools used in pruning and handling host plants may move from the quarantined area if disinfected with one part liquid household bleach (sodium hypochlorite) to four parts water or some other suitable disinfectant.

TDA has guidelines regarding importing palm trees from Florida. Visit www.texasagriculture.gov/RegulatoryPrograms/ PlantQuality/PestandDiseaseAlerts for more information.

Battling Another Disease

As the state fights to contain lethal bronzing, it’s also on guard

against another devastating plant disease — lethal yellowing,

which targets coconut trees and hasn’t yet been found in Texas.

The entire state of Florida, the Commonwealth of Puerto Rico,

and the Territory of Guam are under quarantine for lethal

yellowing disease.

“One of the main reasons lethal yellowing hasn’t spread

to Texas may be because we don’t really have coconuts here.

Lethal yellowing has been found in Louisiana, which I thought

was surprising. The disease in Louisiana infected some of

the ornamental palms, not coconuts. Lethal yellowing could

show up on some other type of palm here in Texas,” Dr. Ong

warns.

If you observe any symptoms of lethal bronzing or lethal

yellowing on palm trees, immediately inform the TDA

office nearest you. To find your regional office, visit www.

texasagriculture.gov/About/RegionalOperations. TNLA Green

by CRYSTAL ZUZEK

Palms in Lethal Decline

TDA Q&A: Lethal Bronzing

Lethal bronzing, previously known as Texas Phoenix Palm Decline, has a devastating impact on date palms and other palm species. Infected trees turn yellow, rot, and lose their leaves and fruit before the fruit is mature. No cure for the disease has been discovered. The Texas Department of Agriculture (TDA) has these answers to frequently asked questions to assist green industry professionals in managing this disease.

What types of palms are affected? The regulated palms include:

• Date palm, Phoenix dactylifera • Canary Island date palm, Phoenix canariensis • Silver or sylvester date palm, Phoenix sylvestrisS • Queen palm, Syagrus romanzoffiana • Cabbage palm or sabal palm, Sabal palmetto

What can Texas nurseries do? Nurseries can monitor for symptoms of lethal bronzing on quarantined palms, whether grown in Texas or imported from other states. If you observe suspected symptoms, notify the nearest TDA regional office for inspection and diagnosis. To find your regional office, visit www.texasagriculture. gov/About/ RegionalOperations.

Which Texas counties are under quarantine? These Texas counties are under quarantine:

• Cameron, Hidalgo, Nueces, and Willacy counties • Infected portions of Kleberg County • Parts of Harris County

For updated quarantine information, visit www. texasagriculture.gov/ RegulatoryPrograms/ PlantQuality/ PestandDiseaseAlerts.

Who can I contact for more information? Questions may be directed to TDA’s Gulf Coast Regional Office in Houston. Call 713.921.8200.