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Palm economies threatened by insects and diseases

May 18, 2014 - 12:05am

We traveled through West Africa to get an 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 pest spreading into the region, the red palm weevil. We met with researchers and learned that not only is it killing palms around the Mediterranean, but it has been discovered in Florida and California, as well.

Next week, several members of the International Palm Society from Hawaii will attend a conference in Miami. One of the topics to be discussed is how to control this destructive pest.

Palm society tours include those of the Amazon, Cuba and Trinidad. This part of the world has rare and threatened native forests much more diverse than our forests in Hawaii. Many palms are found in these places, and some are yet to be discovered. Throughout tropical America, the most common varieties are coconut palms and African oil palms. Most folks there depend heavily on the products of these species. 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. The African oil palm has been planted for oil export at the expense of loss in native forests.

We are fortunate to have few diseases and pests of palms in Hawaii. The Department of Agriculture is always on the alert for pests and diseases like the one that hit south Florida several years ago: lethal yellowing. This disease killed most coconut and other susceptible palms in Florida and many other areas of the Caribbean.

So far, we have not found one case of lethal yellowing disease in Hawaii and hope that continued vigilance on the part of the Department of Agriculture and Hawaii’s citizens will ensure our freedom from this devastating plague.

Hawaii’s palms may 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 are suffering from lack of fertilizer or water. The trees need a balanced fertilizer plus minor elements, applied three to four times per year, and regular irrigation.

Lethal yellowing hit Key West, Florida, in the 1950s. After a number of years and killing three-fourths of the coconut palms, it stopped. In the 1970s, it was found in the Miami area. By 1980, most coconut palms in South Florida were dead.

Research at the Coconut Industry Board in Kingston, Jamaica, has shown 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 Jamaica tall coconut is about 100 percent susceptible. On the other hand, the dwarf types are only slightly susceptible. Crosses of the dwarf and tall varieties are fairly resistant.

According to the University of Florida, other susceptible trees include Manila, fishtail, loulu, date and oil palms.

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 scientists. They appear to be transmitted by a leafhopper. Neither the disease nor the 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 resistant to the disease, requires more care and is more subject to scale infestation in Florida. 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. Today, South Florida again has coconut palms gracing its beaches.

The International Palm Society and University of Florida cooperated on a project to plant more palms not susceptible to the disease.

The Hawaii Chapter of the International Palm Society and commercial palm growers have also introduced new palms. We probably have more species of palms in Hawaii than any other place in the USA.

Transporting plants, especially palms from affected areas, could introduce pests and 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 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, and be aware that there are stiff fines for bringing plants or animals into Hawaii without the proper permits and inspection.

For more about the Hawaii Island Chapter of the International Palm Society, contact President Tim Brian at 333-5626.