Why Is My Foxtail Palm Tree Yellowish in Color?
The foxtail palm tree, or Wodyetia bifurcate, is the most common palm in the southern U.S. The tree is native to a remote area of Queensland in northeastern Australia, and was unknown to all but the aboriginal people until 1983. Growers smuggled seeds out of the country until export was legalized in 1995.
The Foxtail Palm Tree
This fast-growing tree can gain as much as three feet of trunk height a year, reaching approximately 30 feet at maturity with a bushy 20-foot spread of full, dark green, feather-like -- properly called pinnate -- fronds; the crown usually consists of 10 to 12 fronds. Considered by some experts to have the most spectacular of all palm tree showings, these fronds can reach up to 10 feet in length. Experts at the University of Hawaii note that full growth is usually reached at around 12 years. The slender, gray solitary trunk is smooth and self-cleaning. Cream-colored inflorescences give way to massive clusters of 2-inch-long fruits that ripen to a bright red. Foxtail palms thrive both in full sun and partial shade and, although their untypically deep root system makes them very resistant to environment vagaries, they do best in Zones 10 and 11.
Epidemiology of Lethal Yellowing
Lethal yellowing is a disease caused by Phytoplasma bacteria delivered, according to the University of Florida, by insects. According to Forrest Howard, an associate professor of entomology, and Nigel Harrison, an associate professor of plant pathology, both at the University of Florida, the disease has been known in the Caribbean since the 19th century. It likely entered North America through Key West in the 1930s, where it killed approximately 75 percent of all coconut palms. An epidemic then spread north along the Florida seaboard, killing more than 100,000 trees over the following half century. As the disease most commonly affects coconut palms, an outbreak can have catastrophic effect on local economies.
Effects of Lethal Yellowing on Foxtail Palms
Lethal yellowing disease is uncommon in foxtail palms, but University of Hawaii experts note that they will occasionally succumb to it. Fronds will first turn yellow then die off, and the tree will likely die within six months. The first symptom of the disease in foxtail palms is a darkening of the inflorescences, which eventually become dry and gnarled. Older fronds, then younger ones, dessicate, change color from green to yellow and droop. Lastly the bud will begin to rot; although some younger fronds may still be bright green at this stage, the tree is effectively dead. Full process, from first signs of infection to tree death, takes between three and six months.
Treatment of Lethal Yellowing in Foxtail Palms
The condition should be addressed immediately with injections of oxytetracycline-HCL, which should be available from most garden centers in areas where the trees are commonly seen, and from specialist palm tree nurseries. Howard and Harrison note, however, “this treatment is not curative, and must be repeated every three months to keep the disease in remission.” They also recommend seeking information on types of native palms that are immune to lethal yellowing disease from county extension services.
Additional Information on Disease in Foxtail Palms
Dark, circular lesions on the fronds, called leaf spot, are caused by a fungus that preys on nitrogen- and iron-deficient trees. Treat by restoring the tree’s full vigor with regular palm fertilizer or, in extreme cases, the application of copper spray according to the manufacturer’s instructions.