Gardening: A deadly, contagious palm tree disease
Lethal yellowing is a deadly and very contagious palm tree disease. Collier County and Marco Island both have the disease present in their areas. In the past they declared an emergency relating to this disease.
It became a serious problem in Jamaica and the Florida Keys in the 1950s. In Key West 75 percent of the coconut palms were destroyed. During the 1960s, the disease and interest in it died out in Key West.
It reappeared in 1969 in Key Largo and by 1971 several trees were infected in Coral Gables. Within months the disease had killed a thousand trees in Miami. It had traveled to Broward County by 1972 and to Collier and Martin Counties by 1974.
Lethal yellowing has killed nearly all of the “Jamaican Tall” coconut palms in Dade and Broward Counties. But Palm Beach County lost only 30 to 40 percent of their coconut palms due to successful antibiotic injection programs.
Resistant coconut varieties have been replanted in these areas and along with the “Jamaican Tall” palms which survived, the tropical atmosphere has been restored to the Florida Keys and the East Coast. The west coast of Florida still has most of its “Jamaican Tall” coconut palms but lethal yellowing is obviously a constant threat to our area. Confirmed cases of the disease have been found in East Naples, Port Royal, and here on Marco Island.
This disease also affects many other palm trees. Some of the more common include the Fishtail palm, Cabada palm, Spindle palm, Chinese Fan palm, Canary Island Date palm, Date palm, Senegal Date palm, Chinese Windmill palm and the Christmas palm.
Symptoms of lethal yellowing can be confused with other maladies of palm trees including fungal bud rot, nutritional deficiencies, insect or lightening damage. However, here are the four definite symptom stages of lethal yellowing in coconut palms.
The first symptom is premature dropping of most or all of the coconuts. This is called shelling and most of the fallen coconuts will have a brown or black water soaked area immediately under the outer covering.
The second stage, which is classic lethal yellowing, is the blackening of the flower stalks. Healthy flowers are golden or creamy yellow as they break out of the casing they are enclosed in. Most diseased male flowers will be dead on the blackened flower stalks and no fruit (coconuts) will set.
In the third stage, from which the disease gets its name, the fronds turn yellow, usually beginning with the oldest fronds and advancing upwards through the crown. In some cases one single frond in the center will turn yellow first giving a characteristic flag appearance. These yellow fronds will die, turn brown and hang down. They will fall off or can be easily pulled off.
Death of the bud occurs about halfway through the symptom stages. The new frond emerging from the center will collapse and hang down from the crown. The entire top of the tree will eventually fall off leaving a “telephone pole” tree. The whole process takes three to six months from the first symptom to death.
Other palms will have the first two symptom stages that the coconut palms have, premature dropping of fruit and blackened flower stalks. However, the discoloration of fronds may differ. Some may have fronds which turn a greyish-brown rather than yellow. Often one frond will turn yellow or brown first giving the flagging appearance.
Lethal yellowing is caused by single-celled mycoplasma-like-organisms which attack the food conducting tissues of palm trees. These organisms are transmitted from tree to tree by a plant hopper identified as Myndus crudus.
Insecticides will slow the spread of the disease but they are not sufficiently effective in controlling it. Antibiotic injections are a sure way to protect your trees from this disease. It was mandatory in Collier County for years but is now up to individuals whether or not they inoculate their trees. Because the disease is on Marco Island, everyone should have their trees inoculated for this deadly palm disease. If you own a lawn maintenance or landscape company you should notify all of your customers about this problem and suggest treatment. And if you see a suspect tree please call the Collier County Extension Office at 252-4800.
For treatment you can contact most horticultural spray companies or the Collier County Extension Office for referrals to companies offering this service. It costs only dollars per tree and once on a schedule most companies will automatically return for your next treatment. It doesn’t get any easier or cheaper so call today.
Eileen and Peter Ward have owned a landscape and lawn maintenance company for 35 years. Eileen can be reached at Gswdmarco@comcast.net or 239-394-1413.