Palm breach

Abstract

A pest spreading rapidly amongst iconic and economic palm trees highlights the difficulty of eradicating exotic pests. Nigel Williams reports. A pest spreading rapidly amongst iconic and economic palm trees highlights the difficulty of eradicating exotic pests. Nigel Williams reports. Exotic pests, long a problem, are becoming increasingly troublesome as global trade develops, climate changes, and pressure on funds needed to tackle the problem grows. One species currently causing particular concern is the red palm weevil. A pest, originally from South East Asia, spread by the trade in palm trees, has claimed its latest victims in its move across the Middle East and Europe, where it is causing millions of dollars of damage to both food and ornamental crops. Council authorities in Malaga, at the heart of Spain's tourist industry, announced last month that Canary palms in its popular central gardens were infected with red palm weevil and would have to be destroyed — an approach that has seen thousands of trees destroyed elsewhere.Killed: A young phoenix palm in Favignana, an island close to Sicily, is victim to the spreading red palm weevil. (Photo: Mary Devane.)View Large Image Figure ViewerDownload Hi-res image Download (PPT) The red palm weevil was first spotted in 1891 in India and was recognised as a serious pest of the coconut palm in 1906. By 1917 it was described as a pest of the date palms in Punjab. But, in recent decades, it has spread to the Middle East and Europe as the trade in palm trees has developed and infected trees are hard to identify. Standard ‘phytosanitary’ procedures used by most countries to prevent the trade in diseased plant materials have often failed, leaving infected material unidentified. The red palm weevil is a lethal pest of palms reported to attack at least 17 species, including coconut and date palms. Infected palms, if not detected and treated early, often die. However, palms in the early stage of attack respond to chemical treatment with insecticide. But the trouble lies in identifying them. Weevils seem to prefer palm trees that are under 20 years old, as the stem of the young plant is soft and can be penetrated easily. An adult female beetle enters the crown of the tree and lays up to 300 eggs. It can also lay eggs in cracks where offshoots emerge. The eggs hatch in two to five days and the larvae bore into the interior of the palms feeding on the tissue. The larvae live for one to three months before pupating and then emerging as adults two to three weeks later to restart the life cycle. Adult weevils are thought to be able to fly little more than a kilometre, so the spread of the pest is thought almost entirely to be the result of trade in infested plants. In the Middle East, the date palm tree has a cultural, religious and economic significance. According to the UN's Food and Agriculture Organisation, Egypt is the world's biggest date producer, contributing 17 per cent of the world's total. It is closely followed by Iran (14.5 per cent), Saudi Arabia (13 per cent) and the UAE (12 per cent). Iraq, once home to around 40 million date palms of 624 recognised varieties, used to be the largest date exporter. But the Iran–Iraq war in the 1980s, the first Gulf War, trade sanctions and the current US-led invasion have substantially reduced the number of trees and output. The top nine date-growing countries are in the Middle East and North Africa, making the weevil a threat to one third of the world's date production. Red palm weevils have been identified in Egyptian palms since 1992. The fact that this problem still persists 16 years later, with no method of complete eradication or early detection, has been labelled by many agricultural scientists as ‘very worrisome’. Research on ways to control the weevil are being carried out, but, because the fruit from date palms is harvested for human consumption, options for this species are limited. And Egypt is an exporter of ornamental nursery specimens vulnerable to attack too. “Pests and diseases spread increasingly with the expansion of trade and travel in the globalising world system,” says Peter Kenmore of the FAO Plant Protection Service. So far, no country has been able to eliminate the weevils completely. The use of insecticides has led to the development of strains that are resistant to some of the chemicals used. Palm trees in Turkey are being threatened by red palm weevils, Turkish authorities announced at the end of last year. The weevil there has already caused damage worth millions of Euros, they believe. The Turkish agriculture ministry has banned the import of palm trees but the fight is still on, with six provinces in Turkey being quarantined. Other European countries have also imported palms and are likewise struggling to eliminate the weevil threat, the Turkish authorities say. Turkish officials are now considering felling their infected palm trees as the most effective control method. Most scientists suggest destroying the infested trees, cultivating uninfected trees and issuing certificates for them — and banning palm imports entirely. Last month, the cabinet of the UAE government banned the import of palm trees from any country where red palm weevil had been identified. “This is a great danger for the date palm industry,” said Abdul Wahab Zaid, the director of the date palm research and development unit in the UAE. “Ideally, movement of planting material from infested plantations within the country and also from one country to another needs to be stopped. Wherever this is not possible, it is essential to implement strict pre- and post-entry quarantine regimes wherein only pest-free and certified planting material can be transported,” writes J.R. Faleiro, at the Plant Protection Laboratory, ICAR, in Goa, India, for the Red Palm Weevil Forum. One of the major worries about the weevil's arrival in Europe is the last remaining population of the Cretan date palm, which is found in Vai in the north-east of the island. In 2006 the weevil was found in many parts of Greece, including Crete. Researchers suspect that the import of many palms ahead of the Athens Olympics in 2004 may have been a source of the pest. In Malta, like Crete, which has critically endangered populations of native palms, there has been widespread concern about the weevil. “It came fairly easily. But eliminating and controlling it is almost impossible,” the Times of Malta recently reported. “Measures necessary to control this introduced alien species are expensive, as with all other alien species. One wonders if the entrepreneurs who have been directly importing palm trees to the Maltese islands are going to finance such measures to control this species — though perhaps the ecological and economic damage is not so much a concern to them as cashing in on the profits,” the paper said. “It is more realistic than pessimistic to conclude that at the end of the day, it will be common families who will eventually have to dig deep into their pockets to pay for the hidden costs. The prevention and control of the introduction of alien invasive species is being handled without any national strategy, without any policy, without any vision but with one driving force — short-term financial return. Who will be paying for such mismanagement?”