Palms in Lethal Decline Texas works to contain lethal bronzing, prevent lethal yellowing from wiping out palm trees 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,
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TNLA Green March/April 2020
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
