Melolontha spp.

Melolontha spp.

1. Identification

• Common name: cockchafer, white grubs, May bug
• Scientific name: Melolontha melolontha L. and Melolontha hippocastani Fabricius
• Order: Coleoptera
• Family: Scarabaeidae

2. Description of the pest

• Adults: robust beetles, 20–30 mm; reddish-brown body; brown elytra; antennae with well-developed lamellae (more evident in males).
• Larvae: white, “C”-shaped, with a brown head and well-developed legs; they reach 40–50 mm; they live in the soil and are responsible for the main damage.
• Pupae: form in the soil, in pupal chambers.
• Eggs: laid in the soil, in groups, at a depth of 10–20 cm.

3. Main hosts

• Agricultural crops: potato, maize, various vegetables.
• Fruit trees: pome fruits, stone fruits, soft fruits.
• Vines.
• Meadows and pastures.
• Forest species: oak, chestnut, beech, pine.
• The larvae are highly polyphagous, feeding on the roots of many plants.

4. Symptoms and damage

• Wilting and death of young plants due to root consumption.
• Reduced vigour and slow growth in trees and shrubs.
• Plants that come away easily from the soil due to root destruction.
• In meadows: patches of dry grass that detach easily.
• Severe damage in forest and agricultural nurseries.
• Adults feed on leaves, which may cause partial defoliation in trees, but the most serious damage is caused by the larvae.

5. Biological cycle

• Multi-year cycle: generally 3 to 4 years, depending on the species and climate.
• Adults emerge in spring (April–June), with crepuscular flights.
• Eggs laid in the soil; hatching after 4–6 weeks.
• Larvae pass through 3 instars over several years, feeding on roots.
• Pupation occurs in late summer of the final year.
• Overwintering as a larva (in the first years) or as a pupa/adult in the soil.

6. Monitoring

• Soil sampling for the detection of larvae.
• Observation of root damage in sensitive crops.
• Monitoring of adult flights in spring (light traps or direct observation).
• Assessment of larval density in meadows and nurseries.

7. Management measures

• Cultural: soil tillage to expose larvae; crop rotations; avoiding the establishment of sensitive crops in soils with a history of infestation.
• Biological: use of entomopathogenic nematodes (Heterorhabditis bacteriophora, Steinernema spp.); promotion of natural predators (birds, wild boar, hedgehogs).
• Integrated protection: regular monitoring; targeted intervention in areas with high larval density; judicious use of biological and cultural methods.

Bibliographic references

• EPPO Global Database – Melolontha melolontha, M. hippocastani.
• CABI Invasive Species Compendium – Melolontha spp.
• Jackson, T. A. et al. (2000). Biological control of scarab larvae.
• Keller, S. et al. (2003). Entomopathogenic nematodes in the control of soil pests.
• Traugott, M. et al. (2008). Ecology and management of Melolontha species.