Red Palm Weevil

Actually a very beautiful animal, this red palm weevil (Rhynchophorus ferrugineus), is widely found in southern Asia and Melanesia, where it feeds on a broad range of palms including coconut, sago, date, and oil palms. It is a serious pest of palms, particularly coconut. For example in Tamil Nadu, India, yield losses of 10-25% have been recorded in coconut plantations. It is the most important pest of the date palm (Phoenix dactylifera) in the world.

I found this weevil in my garden below a coconut tree ;-). I picked it up using a stick which was held in my left hand. I photographed with camera stabilized in my right hand. I had to balance a quite heavy setup of Canon EOS 5D mark II with Canon EF 100mm f/2.8L Macro IS. Light was provided by Ray Flash Adapter fitted on Canon Speedlite 580EX II. The grey wall you see at the back is in fact the white wall of my house which was around a feet away. Since the light dropped off rapidly from the flash it gave a nice grey background.

On these Photos you might recognize, that mites are transported on the legs of this weevil. This process is called phoresy, which means one animal attaching to another for transportation only. Examples of which are mites on insects (such as beetles, flies, or bees), pseudoscorpions on mammals or beetles, and millipedes on birds. Phoresy can be either obligate or facultative (induced by environmental conditions) commensalism.

Since the 1980s the Weevil has rapidly expanded its geographical range westwards from Southern Asia. It reached Saudi Arabia and the United Arab Emirates in about 1985, spreading throughout the Middle East and into Egypt. In 1994 it was detected in Spain and in 1999 in Israel, Jordan and the Palestinian Authority Territories. It has since spread to the Balearic Islands (2006), Canary Islands (2005), Cyprus (2006), France (2006), Greece (2006), Italy (2004) and Turkey (2007). The two main palm species of concern in the Mediterranean region are date palm and Canary Island date palm (P. canariensis), the main crop and ornamental species, but it also attacks several other ornamental palms that are regularly imported into Britain, such as chusan palm (Trachycarpus fortunei).

Rhynchophorus palm weevils are large insects (usually greater than 25 mm long) which belong to the Rhynchophorinae, a subfamily within the Curculionidae. Adults are large, being up to 42 mm and 16 mm wide, with a long rostrum, characteristic for the weevils. They are reddish-brown in colour with variable dark markings on the pronotum. All life stages may be spent inside the host palm. Each adult female deposits between 200 to 300 eggs in separate holes or cavities on the host plant. Eggs are whitish-yellow, smooth, shiny, cylindrical with rounded ends, slightly narrower at the anterior end, and about 3 mm long and 1 mm wide. These hatch in two to five days, and larvae bore into the interior of the palms, feeding on the soft succulent tissues, discarding all fibrous material. Larvae are legless, with a creamy-white body and brown hard head capsule, and grow up to 50 mm in length. The larval period varies from one to three months. Pupation occurs in an elongate oval, cylindrical cocoon made of fibrous strands, about 40 mm in length. Adult weevils emerge 2-3 weeks after pupation. Thus the life cycle is completed in about 4 months.

Natural and uncultivated areas within southern India, R. ferrugineus is normally a rare and local insect. However, the commercialization of coconut and oil palm growing within tropical Asia, particularly the development of plantation monocultures, has facilitated the range expansion of this insect. Equally the commercialization of date palm growing in the Middle East has created ideal conditions for the rapid spread of the red palm weevil between countries in that region.

Early symptoms of attack are distinctive but hard to see: egg laying notches; cocoons inserted into the base of the palms; an eccentric growing crown; holes at the base of cut palms; symptoms resembling those caused by lack of water such as wilting, desiccation and necrosis of the foliage tunnelling within the stems and trunk. Larvae and adults destroy the interior of the palm tree, often without the plant showing signs of deterioration unless damage is severe. Hollowing out of the trunk reduces its mechanical resistance, making the plant susceptible to collapse and a danger to the public. In most cases, attack on Phoenix and other palms leads to the death of trees whatever their size. Visual examination allows detection of symptoms but cannot determine if there are larvae and adults present inside the trunk. Pheromone traps, acoustic detection or infrared systems can be used to detect this pest.

Economic Importance and Damage Rhynchophorus ferrugineus is a major economic pest of coconut palm, date palm, oil palm and sago palm. It also attacks a wide range of ornamental palms. Severely attacked plants exhibit a total loss of foliage and rotting of the trunk, which eventually results in the death of the tree. Control Measures The availability of effective insecticide treatments against R. ferrugineus are limited. There are several insecticidal treatments that are effective when applied to the soil before planting, but these may be of little/no use as the pest is most likely to be introduced on imported (planted) trees.

Destruction is thus likely to be the only successful eradication measure available. Research into acoustic methods of detection of R. ferrugineus is ongoing, as is research into its control using waveguide (microwave) irradiation. Entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis spp.) may also be effective in controlling R. ferrugineus. Considerable research has gone into the study of these biocontrol agents, but with mixed results. Substantial research has also been carried out into the effectiveness of food baited pheromone traps for the mass trapping of R. ferrugineus, achieving good results on a large scale both in the field and in laboratory tests. The addition of dates to pheromone traps has also been shown to be very effective compared to pheromone alone, in field trials in India.