Extension Service: Yellowing still haunts local county palms

The disease that denuded Key West of coconut palms during the 1930 to 1950 era and moved up to strip the Miami area in the early 1970’s is still active in Collier County. Another outbreak started in October, 2005, in the area between High Point Drive and Solana Road.

In 2006, the county suppression program, per Ordinance 2004-11, has funded the removal of about eight infected coconut palms and initiated 100-yard radius inoculation zones around the palms that were removed. There are currently seven active areas, besides the area just mentioned, we have suppression programs in: Poinciana Village and Coco Lakes; Naples Park (94th to 102nd avenues); Lakewood Villas; Henderson Creek and Collier Boulevard; Isles of Capri and the Queens Park subdivision.

The county is currently inoculating 1,046 coconuts, Christmas and Canary Island date palms, up from last year’s tally of 525 palms, three times a year. The inoculations use an antibiotic labeled for use on palms, oxytetracyline, which helps suppress the development of the disease organism.

Citizens are not required to pay for the removals or inoculations. However, the stumps will not be “ground out” as they pose no threat in the spread of the disease. Please report suspicious palms that are in the county, but are outside of the city limits, to me at 353-4244.

If palms are Inside the city limits, call Joe Boscaglia, 213-7123. Please report suspect PLY palms on Marco Island to the Environmental Specialist, Nancy Richie (389-5003). We have also hired a part-time PLY scout, to more closely monitor the “hot spots” four times a year in a grid-like fashion, street by street.

Please don’t call if it is a queen, royal or cabbage palm, as this is one disease these species and other native palms do not get! Also, Washingtonia, areca, Alexandra, Carpentaria, Ptychosperma, foxtail and pygmy date palms have not been reported to succumb to this disease. However, the disease has been reported to attack 38 other species of palms and screwpine (Pandanus spp.).

There are no resistant coconut varieties, other than a very slow growing and unavailable ‘Fiji Dwarf’ coconut. To avoid bringing infected palms into our county, it is advised NOT to purchase palms grown east of the Collier County line. There is less incidence of PLY in palm nurseries in the gulf coast areas. Other areas have severe problems with this disease and importing palms from infected areas has caused large losses of palms in Collier County. The disease is not spread mechanically on pruning equipment.

As part of the suppression program, the county will remove a dying palm, if it is caught early and still has some green fronds. A plant hopper vectors the wall-less prokaryote (phytoplasma) which causes the plant disease, much like mosquitoes vector human diseases. If there is no green left in the fronds, the little plant hopper won’t feed on the palm nor be able to spread the disease. Thus, the palm is not a threat if it has gone brown, that is, has died. Some palms were not called in before they died and the homeowner had to pay for their removal.

The phytoplasma flourish inside the palm and plug up the vascular system. Palms die rapidly, within five to seven months. If the coconut palm still has fruit, I don’t usually consider it a high probability of being infected. Symptoms vary with the coconut cultivar and palm species. Usually two of these symptoms are a strong indication of a PLY-infected palm:

Coconut palms: Fruit drops and the stem-end is blackened and water soaked.

Coconut palms: Flower tips emerge chocolate brown and droop instead of being held upright.

‘Jamaican Tall’ coconut: Third or forth new leaf turns yellow; oldest fronds drop parallel to trunk; no leaf wilt symptoms. ‘Malayan’ or ‘Maypan’ coconut: Wilt symptoms only, with individual leaflets wilted and folded up; mid-canopy fronds turn brown and droop; there is no yellowing.

Christmas palm: Similar to Jamaican Tall, but without yellowing; oldest leaves may bronze.

Pritchardia (Thurston and Fiji fan palms): death of spear leaf is first symptom.

For pictures of Lethal Yellowing symptoms, information on sending samples for laboratory analysis and inoculators that are using currently approved methods, see: collier.ifas.ufl.edu/Horticulture/LethalYellowing2003.htm

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Doug Caldwell is landscape horticulture agent for the University of Florida, Collier County Cooperative Extension Service. For more information on home gardening, contact its Master Gardener Plant Clinic at 353-2872. For specimen identification, the clinic, at 14700 Immokalee Road, is open 9 a.m. to noon and 1 p.m. to 4 p.m. Monday, Wednesday and Friday; call 353-2872. Web site: collier.ifas.ufl.edu.

© 2006 marconews.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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