Red Palm Weevil in Palm Trees: Characteristics and Control

Several countries classify the red palm weevil as one of the most dangerous crop pests. Therefore, it is crucial to have a thorough knowledge of this species.

Written and verified by the biologist Cesar Paul Gonzalez Gonzalez.

Last update: 01 May, 2024

The red palm weevil is an insect known to infect financially important palm trees. For this reason, it’s considered a pest that can put certain crops at risk. Despite its size, it’s a voracious parasite capable of killing its host and spreading rapidly. In fact, it has managed to reach other countries where it wasn’t naturally distributed.

The scientific name of this species is Rhynchophorus ferrugineus. It belongs to a family of phytophagous insects, known to contain pest species such as the banana weevil (Cosmopolites sordidus), the walnut weevil (Curculio nucum) and the coffee borer beetle (Hypothenemus hampei). Learn more about this insect and how it affects plants in the following article.

Why is the red palm weevil so “dangerous”?

The red palm weevil beetle is an insect that feeds on various plants, especially the palm family (Arecaceae). Although it seems harmless, this pest is characterized by penetrating the stems of its host (the plant) and feeding on its interior. This causes the plant to weaken progressively and it can even wilt.

The biggest problem we face with this beetle is the difficulty in detecting its presence. It develops almost its entire life cycle inside its host and only comes out when it is an adult. In addition, during the first days of infection, the plants show no obvious symptoms or damage.

Most cases are detected when the infestation has become severe.

At this point, the development and reproduction of the weevil beetle has advanced so far that it may have infected nearby palms. Also, internal damage to current hosts tends to be irreversible, so it’s almost impossible to save them.

Species that infest

According to the manual Weevil Management: Rhynchophorus palmarum L. published by Produmedios, this species not only feeds on palm trees, but also on 31 plant species belonging to 12 different families. Among the most important are the following:

• Coyol palm(Acrocomia aculeata)Sacharum officinarum
• Chontaduro palm (Bactris gasipae)
• Moriche palm (Mauritia flexuosa)
• Date palm (Phoenix dactilifera)
• Royal palm (Roystonea oleracea)
• Papaya (Carica papaya)
• Sugar cane (Saccharum officinarum)
• Banana tree (Musa x paradisiaca)
• Pineapple tree (Ananas comosus)
• Cocoa (Theobroma cacao)
• Mango tree (Mangifera indica)
• Avocado tree (Perseaamericana)

Although the red palm weevil can feed on different plants, only on palm trees and sugarcane does it act as a parasite. In all other cases, it occasionally feeds on ripe fruit, so it doesn’t cause significant damage to the crops and fruit.

What does the red palm weevil look like?

The red palm weevil is a large beetle measuring between 2 and 5 centimeters (1 to 2 inches) in length. Its body is oval and is characterized by a “horn” extending from the center of its head. This, in turn, is dimorphic and in males it also has several setae (hairs) that make it look like a brush, while in females it is smooth (without setae).

As its name implies, this beetle exhibits a reddish-brown coloration, with or without black spots all over its body.

However, according to the technical manual of Integrated Control of the Red Palm Weevil Rhynchophorus ferrugineus, the color may become duller or brighter, depending on the population concerned.

The morphology follows the same pattern as that of other coleopterans. According to a publication in the IDE@ magazine, the bodies of this group of insects divide into three distinct parts

• Head: The apical part of the body; it contains the antennae (club-shaped), the eyes, and the mouthparts.
• Thorax: A section of the body partly covered by the “wings” (elytra) of the specimen. All appendages, both legs and wings, are connected to it.
• Abdomen: Posterior part of the body. It’s the longest and most notable area, which lacks appendages and is responsible for protecting most of the organs, including the reproductive organs.

The appearance of larvae and pupae

The red palm weevil is a holometabolous creature that goes through different stages (phases) before reaching adulthood. This means that it undergoes a complete metamorphosis, so during an infestation it isn’t always possible to see it in the form described in the previous section. The appearance of these “pre-adult” stages is detailed below:

Larva

The larva is worm-like (vermiform) and white in color, but becomes yellowish as it grows. It is apodous (legless), has 13 segments (divisions) and a hard red or brown head at the tip of its body.

As mentioned in a publication of the journal Agrària, Comunitat Valenciana, this stage lasts a variable length of time (between 70 and 200 days) and reaches a length of 5 centimeters (2 inches).

Pupa

The pupa is a stage that consists of wrapping the main body with fibers from inside the palm tree. As a result, a “cocoon” is formed that shelters the larva while it carries out the restructuring of its entire body (metamorphosis).

Where can the red palm weevil beetle be found?

Although its origin still isn’t completely certain; several specialists suggest that the red palm weevil originates from the Asian continent. According to the Handbook of Major Palm Pests: Biology and Management, some genetic studies of the species suggest that it comes from the Indo-Malayan region.

Regardless of its origin, this beetle has been reported in several countries and islands in Europe, Africa, America, Oceania and Asia. This is mainly due to the export of infected palms, which spread the beetle and allow it to colonize crops.

The only thing the red palm weevil beetle needs to survive is a temperate climate and the presence of its hosts (palms).

Symptoms of infection in palm trees

Although infection by the red palm weevil isn’t very evident; there are several symptoms that may suggest the presence of this insect. Of course, a thorough inspection of the palm tree is necessary and you should watch for the following signs:

• Wounds on young leaves
• Displacement of young and mature leaves (loss of leaf symmetry)
• Damage at the base of the palms
• The presence of sawdust
• The presence of larvae or adult beetles

It should be noted that these symptoms are not general and vary according to the species of palm tree affected. However, it is always good to be aware of any anomaly in the plant to proceed to eradicate the problem.

Control strategies

The management and eradication of the red palm weevil beetle can be done with one of the three main strategies, which are mentioned below:

Cultural control (common agricultural practices)

In the case of palm trees, pruning causes the release of pheromones that attract the beetle. Therefore, it’s advisable to avoid heavy pruning and seal cuts with mineral oil.

Biological control

There are several types of nematodes and bacteria that act as control agents by attacking the beetle larvae. However, as mentioned in a paper published in the journal Insects magazine, this method depends on several factors to be successful.

Therefore, the field effectiveness of biological controllers is still quite limited.

Chemical control

It consists of injecting insecticides directly into the trunk of the palm trees. The effectiveness of the chemicals varies in each case, because some are focused on destroying a specific life stage of the beetle (larva, adult or eggs).

In addition, according to an article in the International Journal of Agriculture and Biology, the coleopteran has demonstrated the development of resistance to several insecticides.

What to do when faced with an infestation?

The main recommendation when faced with a red palm weevil infestation is to ask for help from professionals. The management of the pest isn’t complex, but it is necessary to be diligent, constant and act at the right time. Also, the population of this coleopteran can generate resistance if the following insecticides are misused:

• Carbaryl
• Fipronil
• Imidacloprid

Professionals usually combine more than one strategy to eradicate the beetles inside the palm tree. After this, the infected specimen is removed, crushed and burned to reduce the possibility of contagion to the rest of the crops.

It should be noted that several countries have specific phytosanitary alerts for when the red palm weevil beetle is detected in the crops. If its presence is confirmed, contact the corresponding health authorities in your community.

The impact of the red palm weevil

As can be seen, the red palm weevil beetle is a dangerous species for palm plantations. Even if detected in time, losses can easily amount to more than a quarter of the total crop. Therefore, one should be alert to any sign of infestation and call in a professional pest expert to eradicate it.