The Evil Weevil is a Red Palm Weevil

Readers Mail….
From A.A. Wisley….

With an acrobatic leap my dog snatched a flying insect in midair and deposited it, almost undamaged, at my feet. Recently, I had seen one or two beetles very similar to the one waving its legs in front of me. Although it was a rather attractive insect I suspected that it was one that I did not want in my garden. It was one of these:

It is the Red Palm Weevil (“RPW”).

The red date palm weevil causes immense damage in date plantations in Asia and Africa and now also in Europe. About 40 varieties of palm, not just date palms can be affected. The weevil can rapidly kill even isolated specimens in a garden or park. I planted a date palm in my garden and just as it was achieving its “architectural” magnificence, after seven or eight years of growth, it succumbed to these bugs and collapsed into a heap of smelly rotten wood. The nearest date palm was several hundred metres away.

It is thought that the RPW hitched a lift on palm trees imported into Cyprus some years ago to decorate the streets of Girne. Since then it has spread rapidly. The weevil is a good flyer and has been measured travelling more than 50 km in a day although it’s usual journeys are much shorter especially if there is a good supply of palm trees nearby. Because it is so mobile its control and eradication is extremely difficult. Commercial growers go to extraordinary lengths to prevent, cure, eliminate and quarantine possible infestation.

The female weevil enjoys a vigorous sex life for a couple of months depositing many eggs in holes she bores into the soft parts of the palm. When the larvae hatch they chew their way into the palm tree creating bigger and bigger holes as they grow. They feed on the sap of the plant and interfere with the flow of nutrients to the plant itself. This eventually leads to the decay and then death of the tree. When the adult beetle emerges from its pupa it flies off to find a mate and a new source of food. The peak activity occurs in April and May and also in September and October. Now, in March, it is a good time to check on any date palms that are growing in your garden and take steps to prevent the plant being affected or, if it is already infected to try and cure the invasion, if that is possible.

Below are images of typical RDW caused damage in date palm ( Phoenix dactylifera ) orchards in Saudi Arabia as published in Biology and Management of the Red Palm Weevil, Rhynchophorus ferrugineus by Research Gate. All rights of authors are acknowledged.

Top left: Damage hole seen before excavation; Bottom left: same palm after excavation and cleaning showing a large hollowed-out cavity and toppled palm. Top right: an adult RPW near a damage hole at the base of the stem, Bottom right: brown viscous ooze coming from stem, indicating RPW infestation (Photos: P.S.P.V. Vidyasagar.)

Prevention

Prevention can include placing a pheromone trap to catch any weevils flying by. The number of bugs caught in a trap will give you some idea of their prevalence and the risk that they pose. It seems you can make a simple trap yourself by drilling three or four holes big enough for a weevil to pass through in a lidded container, ideally red or black in colour. Inside the container you place about a litre of water and, say, half a dozen dates, perhaps also some alcohol. As the dates decay they give off an aroma which the weevil cannot resist. After entering the trap they slip into the water and drown. Adding an insecticide may also help provided that it does not mask the aroma of the decaying dates. The second stage of prevention is to thoroughly spray the trunk and the petioles (where the leaf joins the trunk) with an appropriate insecticide to kill any of the beetles lurking on the surface of the plant. Ideally this should be repeated several times during the year.

On a careful examination of the tree it should be possible to spot the boreholes made by the insects which have already penetrated the tree. Often there will be a tell-tale sign of an ooze and an accompanying unpleasant smell. In fact, sniffer dogs are used on plantations to nose out infected plants. The infestations frequently take place around the petioles and on the soft parts of offshoots, which are particularly vulnerable.

Treatment

The treatment for an infected tree will depend on the severity of the infestation. Treatments range from simply squirting insecticide (or biological agents) into the holes of a small recent infestation, then plugging them; digging out the rotten wood and larvae of a larger problem and backfilling the hole with inert material containing insecticide or, inserting tubes into the trunk of the tree through which appropriate insecticides are administered.

If it is no longer possible to cure the tree it must be removed and the affected sections destroyed to prevent the adult weevils from moving to new territories.

It is a pity that such an attractive arthropod can cause so much damage but consider that Nature does not have a conscience. Of course, the increase in the number of these insects and their spread is entirely due to humans creating vast food resources for them, in date palm plantations, and then carelessly exporting infected palm materials throughout the world.