I have written about this beetle before, and as it is still around, it is worth mentioning again. The Red Palm Weevil (Rhynchophorus ferrugineus), or RPW, is a reddish-brown beetle about 3.5cm long, originally coming from Southeast Asia. This little pest is a Coleopteran snout beetle, with a slightly comical snout and elbowed antennae, with larvae that are fat, white, legless comma-shaped beasts, almost blind and apparently interested only in palm trees as food.


Where do they come from?

Imported palms that are already infected are likely, probably moved in their various growth stages hidden inside palms. They are strong fliers, can migrate to new locations once grown and are capable of moving up to 7 km in 3-5 days, so don’t rest easy if you think you don’t have an infestation. Their dark side is that they have the potential to infest other palm trees, including yours if you have any, and are becoming a severe agricultural problem that might need the help of an expert to deal with.

You may have seen palms with leaves sparse or missing completely, leaving just an ugly trunk, which eventually has to be removed. These palms may have been in place for years, and some owners, on discovering their palm is infected, chop it down, but unfortunately, the beetles will just jump ship to another tree and chomp their way into that one too.

If it feels comfortable and has enough food, the weevil will send out pheromones that will attract even more bugs, and the female can place up to 200 eggs in the space between the trunk and the leaves or in wounds resulting from cutting green palm branches.


Hard to Eradicate

The concealed feeding habit of this little borer is the main reason why spraying environmentally harmful insecticides doesn’t control the pest. Insecticides can be injected directly into palm trunks, or a systematic insecticide added to the soil helps to eliminate the weevils in the egg stage but must be repeated two or three times every year. Natural predators would seem a good option, having over 50 natural enemies, with fungi being the most promising ones for biological control.

Sadly, the RPW has a broad range of palms it will live on. Among these in Portugal is the Phoenix canariensis, a feather palm that can reach up to 15m and is an important part of Portugal's scenery. This handsome tree is one of the most significant palms in our local landscape and has been extensively planted, especially in the Algarve, giving an exotic tropical feel to the environment, and if not attended to, the landscape of the Algarve will change as many of these majestic palm trees fall victim to the weevil and die.


Signs and Symptoms to look for

Detecting the weevils in the first place is difficult, as when a palm tree shows visible signs of distress, it generally means that the infestation is well-advanced, and it’s probably too late to rescue the tree. Look for leaves with signs of having been chewed by larvae, drooping leaves at the centre of the tree, the crown becoming asymmetrical, sawdust and fermented sap visible, remains of cocoons found, and the base of the leaves that look like they have been eaten or cut short – and maybe the tree just looks as if it has lost its vitality too. Apparently, if you listen closely enough to the trunk of an affected tree, it’s possible you might even hear them munching.

Usually, the female drills a hole for each egg in the crown area of the host plant, and even wounds in the root area could be a preferred storage location for those eggs. After hatching, the larvae drill metre long passages into the trunk of their host plant, eating as they go, causing the entire crown area to eventually decompose.

Red palm weevils have become resistant to many of the chemical treatments used against them and bio-warfare using nematode worms is a potential type of treatment that would seem to be more environmentally safe, with pheromone traps being another option to explore.

Author

Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan