The Red Palm Weevil – another alien species


 

Sunday, 2nd December 2007

 The Red Palm Weevil – another alien species –  Alfred E Baldacchino

The Red Palm Weevil – il-Bumunqar Aħmar tal-Palm – is a relatively large species of beetle about 3cm long. Its common English name is derived from its rusty red colour. Scientifically known as Rhynchophorus ferrugineus, the Red Weevil originates from tropical Asia, but has now spread to Africa and Europe. It reached Saudi Arabia, the United Arab Emirates and Oman in 1985. And by 2006 it was recorded in France and in Cyprus.

The rapid spread of this pest is due to the transportation of infested young or adult date palm trees and offshoots from contaminated to uninfected areas. Egypt supplied, directly or indirectly, thousands of such palm trees each year to Spain and other European countries. There is ample evidence to conclude that the first Red Palm Weevils were introduced into Spain from adult palm trees imported from Egypt. And despite the fact that palm trees, like all other imported plants, must be accompanied by a phytosanitary certificate, adult palm trees can still conceal large quantity of hidden insects and diseases, such as Red Palm Weevil eggs and larvae. Red Palm Weevil larvae can eventually kill the tree host. In fact, it is a most destructive pest of date palms in the Middle East.

The Red Weevil spends all its stages (egg, larva, pupa and adult) inside the palm tree itself. The female weevil deposits 300 eggs in separate holes or in injuries on the palm tree. The eggs hatch after two to five days into legless grubs which bore into the interior of the palms and feed on the soft succulent tissues of palm trees.

The larval period varies from one to three months, after which the grub pupate in an elongated oval, cylindrical cocoon made out of fibrous strands. The pupation period lasts 14 to 21 days, after which the adult weevil emerges – a life cycle of about four months.

The adult is a reddish brown cylinder with a long prominent curved snout, varying considerably in size. It is about 35 mm in length and 12 mm in width. Its leathery forewings are dark red, strongly ribbed longitudinally, covering the hind wings which are brown in colour. The weevils can fly a distance of up to one kilometre.

In a press release issued on 24 October 2007, the Ministry for Rural Affairs and the Environment warned the public of the Red Palm Weevil’s presence in Malta. The question is, how did it get to Malta? The expanse of sea surrounding the Maltese islands is a strong enough natural barrier. But following the importation of hundreds of palm trees to Malta, the Red Palm Weevil took a free ride and established itself as an alien species.

In a previous article, I had drawn attention to the great number of palm trees that are being imported. Some, similar to those in the midst of Mikiel Anton Vassalli regional road, are up to two storeys high. They are easily 60 or more years old and once must have graced some natural oasis in north Africa. Considering the infested trees in Egypt which have contributed to the introduction of the Red Palm Weevil to Spain and Europe, the indications are that this is where it came from. And with such an abundance of food available, who can stop it from dispersing all over the island.

Malta does have indigenous species of palm trees, the Dwarf European Fan Palm – Chamaerops humilis il-Ġummara, whose wild population is critically endangered.

Furthermore there are a number of important Date Palms – Phoenix dactyliferail-Palma, and Canary Island Palms – Phoenix canariensis il-Palma tal-Kannizzati. There are also a number of historical specimens of palm trees growing in a number of private gardens and also in the Argotti Botanic Gardens, San Anton Gardens, among others, most of these planted from seed by the renowned Maltese botanist John Borg. However, all these important indigenous and historical palm trees are now in danger of kissing their roots goodbye.

Dead palm trees – the result of the introduced invasive alien species, the Red Palm Weevil

 

The control of such an alien species is indeed a hard nut to crack. It came fairly easily. But eliminating and controlling it is almost impossible. When the laboratories of the Plant Protection Section of the Department of Agriculture and the Agricultural Research Institute in Cyprus discovered the Red Weevil on its territory, all infested plants were removed and burned. In addition measures were taken to train all plant health inspectors in the identification and handling of infested palm trees.

The ecological, economic, and historical damage will become more evident with time. The damage caused by the Red Palm Weevil’s larva is not immediately visible, and by the time symptoms of such infestation appear, the damage is so advanced that it is difficult to save the tree from death. The population of the Red Weevil cannot but increase with such a large food supply available, and with no official national biodiversity strategy in place.

Measures necessary to control this introduced alien species are expensive, as with all other invasive alien species. One wonders if the entrepreneurs who have been directly involved in importing palm trees to the Maltese Islands are going to finance such measures to control this species – though perhaps the ecological and economical damage is not so much of a concern to them as much as cashing in on the profits. From experience it is almost impossible to convince decision-makers and garden centres to use locally grown specimens for landscaping. Dealers in palm trees and other plants find it more profitable economically to import, and let society carry the hidden costs.

As M. Ferry and S. Gomez (2002) conclude in their paper The Red Palm Weevil in the Mediterranean Area, “… there is a need for phytosanitary regulations at a European and North African country level to forbid totally the importation of date palms.” Will the minister responsible for the Environment and Agriculture eventually stop the importation of palm trees to contain such damage? Who is going to be accountable for any potential additional importation of this alien species and more of its food supply? What action will be taken to prevent the introduction into and the spread within the community of the Red Palm Weevil?

It is more realistic than pessimistic to conclude that at the end of the day, it will be common people 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 (this is not the only species introduced during the last couple of years) 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?

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