Large beetles

Large-sized beetles

1. Identification

• Common name: Various (see individual species sheets)
• Scientific name: Various species from several families of Coleoptera
• Main families: Cerambycidae, Buprestidae, Curculionidae, Scarabaeidae, Dryophthoridae, Brentidae
• Order: Coleoptera

2. General description

• Insects with a robust body, often large-sized and with a strong capacity for boring or root feeding.
• Larvae generally xylophagous or rhizophagous, responsible for the most severe damage.
• Adults with developed mandibles, long antennae (Cerambycidae) or an elongated rostrum (Curculionidae and Dryophthoridae).
• Long life cycles, with prolonged larval stages inside the wood, pseudostem, rhizome or soil.

3. Main hosts

• Anoxia villosa Fabricius – Vine, citrus, fruit trees and ornamentals (larvae in the soil).
• Capnodis carbonaria Klug – Prunoideae and other stone fruit trees.
• Capnodis tenebrionis L. – Prunoideae (apricot, peach, plum).
• Cerambyx cerdo L. – Oak and other large broadleaf trees.
• Cosmopolites sordidus Germar – Banana.
• Cylas puncticollis Boheman – Sweet potato.
• Melolontha melolontha L. and other Melolontha spp. – Various crops; rhizophagous larvae in meadows, fruit trees, vine and vegetables.
• Monochamus galloprovincialis Olivier – Conifers, especially maritime pine and stone pine; vector of the pine wood nematode.
• Oryctes nasicornis L. – Palm trees and decomposing organic matter.
• Rhynchophorus ferrugineus Olivier – Palm trees (Phoenix spp., Washingtonia spp.).
• Scyphophorus acupunctatus Gyllenhal – Agave spp. and other Agavaceae.
• Sitona lineatus L. – Legumes, especially pea and broad bean.
• Xylotrechus arvicola Olivier – Grapevine.

4. Symptoms and damage

• Borings in trunks, branches, pseudostems, rhizomes or roots.
• Presence of extensive internal galleries, sawdust, fibres or gum exudation.
• Progressive decline of the plant, wilting, yellowing and reduced vigour.
• Breakage of branches, sudden death or establishment failures in young plants.
• In rhizophagous species, severe damage to the root system, affecting the absorption of water and nutrients.
• In crops such as banana and sweet potato, destruction of internal tissues essential to development.

5. Biological cycle

• Cycles generally multiannual, with long larval stages protected inside the plant or in the soil.
• Adults emerge mainly in spring and summer.
• Egg-laying in cracks of the bark, base of the trunk, weakened tissues, pseudostems, rhizomes or soil.
• Larvae develop inside the wood, pseudostem or roots, hindering direct control.

6. Monitoring

• Observation of exit holes, sawdust, fibres, gum or galleries.
• Inspection of trunks, branches, pseudostems and roots to detect hollow or weakened areas.
• Specific traps for some species, including the attractants and pheromones for Rhynchophorus ferrugineus, Cosmopolites sordidus and Monochamus galloprovincialis.
• Reinforced monitoring in young orchards, recent plantations, palm trees and susceptible crops.

7. Management measures

• Cultural: They include practices that reduce the susceptibility of plants and hinder the establishment of the beetles. Maintaining plant vigour, correcting water and nutritional stress and removing dead or weakened branches reduce entry points for egg-laying. The elimination of heavily attacked plants, infested wood, deteriorated pseudostems and decomposing organic matter decreases population pressure. In woody crops, avoiding wounds on the trunk and protecting pruning cuts helps to prevent attacks. In rhizophagous species, soil tillage and the management of organic matter limit larval development.
• Biological: They are based on the action of natural enemies that attack larvae or adults. They include larval and egg parasitoids, generalist predators in the soil and entomopathogens such as Beauveria bassiana and Metarhizium anisopliae, effective on several rhizophagous and xylophagous species. In palm trees, the use of entomopathogenic nematodes has shown effectiveness against Rhynchophorus ferrugineus. The conservation of these agents requires practices that preserve functional biodiversity and avoid broad-spectrum insecticides. 
• Integrated protection: They rely on regular monitoring, early detection and selective intervention. The use of pheromone traps allows the detection and reduction of populations of some key species. Treatments should be directed at the adults, the most exposed stage, or applied preventively during egg-laying periods. The localised application of insecticides at entry points or galleries may be necessary in specific cases. The integration of cultural and biological practices and continuous monitoring makes it possible to reduce the risk of severe attacks and keep populations below the damage threshold.

Bibliographic references

• EPPO Global Database – Coleoptera (various species).
• CABI Invasive Species Compendium – Sitona lineatus, Scyphophorus acupunctatus, Rhynchophorus ferrugineus, Monochamus galloprovincialis, Cosmopolites sordidus, Cylas puncticollis, Cerambyx cerdo.
• Ferry, M., & Gómez, S. (2002). The red palm weevil in the Mediterranean area.
• Malumphy, C. (2010). Invasive longhorn beetles in Europe.