Hawaii gardens include hundreds of species of rare palms. As far as the United States is concerned, even the coconut palm can only be grown here and on the southern tip of Florida.
When it comes to species of palms in the world, there are thousands, with more discovered each year.
They come from the high mountains, such as the Andean wax palms that live at 13,000 feet above sea level, to equatorial rain forest species such as those from the Amazon. Desert palms are another large group, but none is quite so close to our Hawaii hearts as the coconut palm.
The coconut palm group is composed of scores of varieties including some dwarf types that should be used more in Hawaii. Not only are they shorter and easy to harvest, they are resistant to a devastating disease referred to as lethal yellowing.
Our endemic loulu palms (Pritchardia species) are very prone to this disease.
Palms here have few serious diseases at present. Hawaii’s palms can be affected by bud rot or stem bleeding disease that is often caused by physical damage such as unsanitary pruning equipment or climbing spikes. Most palms showing yellow or stunted growth have been found to be suffering from lack of fertilizer or water.
For example, a recent report came from concerned citizens calling about the dead and dying trees throughout Kona. The trees simply need a balanced fertilizer plus minor elements, applied three to four times a year, and regular irrigation.
All these problems are correctable, but if lethal yellowing ever gets to Hawaii, there’s no practical way of stopping destruction of our island’s palms. Not only would the coconut palm be destroyed, but more than a hundred species of native and exotic palms would also die.
To realize the full potential threat of lethal yellowing, picture the streets of Waikiki and Kahala with tens of thousands of dying coconut palms in all stages of the disease, from the early brassy yellowing of the lower fronds through the collapsing of the crown and the final “telephone poling,” when there is nothing more than a naked trunk.
This disease, originally thought to be a disease exclusively of coconut palms, occurs in the West Indies, Florida, Texas, Mexico and Africa. A similar disease occurs in the Philippines.
Lethal yellowing hit Key West, Fla., in the mid-1950s. After a number of years and killing three-fourths of the coconut palms, it stopped.
In the early 1970s, it was found in the greater Miami area. Since the Jamaica tall coconut palm is the one that was planted almost exclusively in Florida, the disease ran rampant. By 1980, most coconut palms in South Florida were dead.
Research by the Coconut Industry Board in Kingston, Jamaica, showed that all varieties of coconuts are susceptible to lethal yellowing. The degree of susceptibility has been the point for developing varieties that are resistant. The dwarf types are least susceptible.
When lethal yellowing hit the mainland of Florida, it was discovered that many other palms also were susceptible to the disease in varying degrees. According to the University of Florida Lethal Yellowing Research Station in Fort Lauderdale, hundreds of other palms are susceptible, such as the Manila palm, fishtail palm, loulu palm, date palm, oil palm and many others.
Mycoplasma-like organisms, that occupy a niche between a virus and bacteria, are the cause of lethal yellowing. Mycoplasma-like cells were found in tissues of all diseased palms examined by the University of Florida scientists at the research station. They appeared to be transmitted by a leafhopper.
Remember, neither the disease nor leafhopper have been found in Hawaii.
Hawaii is fortunate to be far from disease-affected regions, but it is vital that we don’t introduce this and other plant plagues.
It is important to cooperate with the Hawaii and federal agriculture departments and follow all the rules of inspection.
