There has been a lot in the press about this evil weevil! Originating in southern Asia and Melanesia, where it is a serious pest of coconuts, this weevil has been advancing westwards very rapidly since the mid 1980s. It had reached the eastern region of the Kingdom of Saudi Arabia in 1985 and by 1994 it had reached southern Spain.
The cause of the high rate that this pest spread is human intervention; by transporting infested young or adult date palm trees and offshoots from contaminated to uninfected areas. The two main palm species concerned are Phoenix dactylifera and P. canariensis, the main crop and ornamental species in the Mediterranean area, but it could attack some others ornamental palms.
There is evidence to suggest that the first weevils were introduced into Spain from adult palms imported from Egypt, where the introduction of the red palm weevil was caused by an importation of offshoots from the United Arab Emirates. Various techniques have been used to try to control the red palm weevil and to save infested date palms, but despite good results, they are not efficient enough to succeed in eliminating red palm weevil. The reason for this is probably the great difficulty in reaching all life stages of the weevil inside an adult palm tree, even with intensive treatment. In Egypt, as well as in the south of Spain, the elimination of infested trees has not been applied systematically as soon as the pests were detected. The possibility of saving these trees and avoiding serious economic consequences as a result of their elimination and the practical difficulties of carrying out this operation, have unfortunately, limited or delayed the destruction of infested trees.
The authorities in Spain, have initiated various actions to combat the pest. Intensive chemical treatments have been used to protect the Phoenix palms and to try to cure affected trees. Preventive treatment of all the palms, even healthy ones, has to be repeated once a month outside the tourist season. Insecticides are injected several times and in various places all around the stems of palms. Simultaneously, a programme of mass trapping of the weevil has been taking place, but despite all these efforts, more than one thousand Phoenix have been killed.
The male and female adults are large reddish brown beetles about 3 cm long and with a characteristic long curved beak-like head. It has strong wings and is capable of undertaking long flights. Damage to palms is produced mainly by the larvae. Adult females lay about 200 eggs at the base of young leaves or in wounds to the leaves and trunks. The grubs feed on the soft fibers and terminal bud tissues of the palm and reach a size of more than 5 cm before pupation. Just before this stage they move towards the interior of the palm making tunnels and large cavities. They can be found in anywhere within the palm, even in the very base of the trunk where the roots emerge. Pupation generally occurs outside the trunk, at the base of the palms, making a cocoon of brown dried palm fibres.
Generally the adult weevils present in a palm will not move to another one while they can feed on it. Usually the damage caused by the larvae is visible only long after infection and by the time the first symptoms of the attack appear, they are so serious that they generally result in the death of the tree. The late detection of the weevil causes a serious problem in the fight against the pest and in any attempt to guarantee pest-free adult trees. Despite research carried out so far, no safe techniques for early detection of the pest have been discovered.
The main ornamental tall palms planted in the gardens and in the streets of the Mediterranean coastal cities are date palms. Thousands of them are imported from Egypt each year, directly or indirectly, into Spain and other European countries. These palms must have a special import passport, but in specimens such as adult date palms, a large quantity of hidden insects and diseases can evidently remain undetected.