Tuesday | June 28, 2016
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Palm economies threatened by insects, diseases

We have been traveling in West Africa to get a firsthand overview of deforestation occurring in countries from South Africa to Senegal.

We ended up in Spain to observe ancient groves of date palms being destroyed by a new insect pest recently spreading into the region — the Red Palm Weevil. We met with researchers working on ways to control the pest and found not only is it killing palms around the Mediterranean, but it was discovered in Florida and California. It is especially devastating to Phoenix species, but can affect many other species.

Next week, several members of the IPS from Hawaii will attend an international palm conference in Miami. One of the topics to be discussed is how to control this destructive pest, as well as other insect and disease pests of palms.

Post tours and pretours include the Amazon, Cuba and Trinidad. This part of the world has rare and threatened native forests much more diverse than our forests in Hawaii. These forests are valuable because they are unique. It is important to protect them for ourselves and future generations.

Many palms are found in these isolated locations. Some are yet to be discovered. However, throughout tropical America, the main palms people see are coconut palms and African oil palms.

Unlike Hawaii, most folks there depend heavily on the products of these species. On some islands and low coastal locations, the coconut palm is the most common tree. Where drinking water is hard to find, folks count on the sweet water of coconuts. Trunks are used for house poles and flooring. Leaves are used as roof and wall thatching.

Some folks would find it difficult to survive without coconut palms. The African oil palm has been planted on plantations for oil export at the expense of loss in native forests. One can drive for many kilometers and see mostly oil palm.

We are fortunate to have few diseases and pests of palms in Hawaii. The Department of Agriculture is always on alert for pests such as the Red Palm Weevil and diseases such as the one that struck South Florida several years ago. It is referred to as lethal yellowing. This is the disease that killed most coconut and other susceptible palms in Florida and many other areas of the Caribbean. We have been hearing a lot about a possible threat to Hawaii’s palms, as well as other tropical and subtropical regions.

There are also several other insect pests we must be on guard to keep out.

And we do have other palm problems.

On checking it out, most of the reports end up being palms with nutrient deficiencies, drought stress and poor pruning practices. These appear to be caused by severe pruning practices in which too many leaves are removed. This combined with water stress is killing the trees. So far, we have not found one case of lethal yellowing disease in Hawaii and hope continued vigilance on the part of the Department of Agriculture and Hawaii’s residents will ensure our freedom from this devastating plague.

There are approximately 5,000 species of palms in the world. Among the most important are the coconut, date, Sago, African oil, acai, peach and Borassus palms.

Hawaii’s palms might be affected by bud rot or stem bleeding disease, which is often caused by physical damage such as unsanitary pruning equipment or climbing spikes. Most palms showing yellow or stunted growth were found to be suffering from lack of fertilizer or water. The trees simply need a balanced fertilizer plus minor elements, applied three to four times per 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. This disease, originally thought to be a disease exclusively of coconut palms, occurs in the West Indies, Florida, Texas, Mexico and parts of Africa. A similar disease occurs in the Philippines.

Lethal yellowing hit Key West, Fla., in the middle 1950’s. After a number of years and killing three-fourths of the coconut palms, it stopped. In the early 1970’s, it was found in the Greater Miami area. Since the Jamaica Tall Coconut Palms 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 at the Coconut Industry Board in Kingston, Jamaica, showed all varieties of coconuts are susceptible to lethal yellowing. The degree of susceptibility has been the point for developing varieties that are resistant. On the one end of the scale, the Jamaica Tall Coconut is about 100 percent susceptible. On the other end, the dwarf types are slightly susceptible. Crosses of the dwarf and tall are fairly resistant.

When lethal yellowing hit Florida, it was discovered many other palms are also 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, including the Manila Palm, Fishtail Palm, Loulu Palm, Date Palm, Oil Palm and many others.

Mycoplasma-like organisms, which occupy a niche between a virus and a bacteria, are the cause of lethal yellowing. Mycoplasma-like cells have been found in tissues of all diseased palms examined by University of Florida scientists. They appear to be transmitted by a leafhopper. Remember, neither the disease nor leaf hopper have been found in Hawaii.

Florida began a two-stage program to replant the affected areas. More than half a million Malayan Dwarf seed nuts were planted. The Malayan, while highly resistant to the disease, requires more care and is more subject to scale infestation in Florida. It also does not grow without adequate watering.

To overcome this difficulty, Florida researchers started a hybridization project crossing Malayan palms with Panama Talls that have shown resistance to lethal yellowing in Jamaica. The resulting Maypan is highly resistant and also grows with more vigor similar to the Jamaica Talls.

Today, South Florida again has coconut palms gracing its beaches. Many Caribbean Islands such as Jamaica have new coconut plantations planted with the resistant hybrids.

Another approach is the addition of other species of palms that showed resistance to lethal yellowing. The International Palm Society and University of Florida cooperated on a project to use more palms not susceptible the disease.

We are fortunate the Hawaii Chapter of the International Palm Society and commercial palm growers such as Jeff Marcus, Garrett Webb, Jerry Hunter, Jan Anderson and many others introduced large numbers of new palms.

There are far too many to discuss here, but we probably have more species of palms in Hawaii than any other place in the USA.

What is the threat to Hawaii of devastating insect pests and diseases?

Transporting plants, especially palms, from affected areas could introduce the disease.

It is essential to work with the Department of Agriculture and plant quarantine folks to have all imported plants inspected. Above all, do not smuggle in plants. This is how we got the spiraling whitefly, banana bunchy top disease and many other serious pests.

Be sure to follow the rules and regulations developed to protect our islands. Also, be aware there are very stiff fines for bringing plants or animals into the islands without the proper permits and inspection.

If you are interested in learning more about palms, contact the Hawaii Island Chapter of the International Palm Society. The president is Tim Brian at 333-5626.

This weekly column is provided by the University of Hawaii at Manoa College of Tropical Agriculture and Human Resources.


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