Japanese beetle

Popillia japonica

1. Identification

• Common name: Japanese beetle
• Scientific name: Popillia japonica Newman
• Order: Coleoptera
• Family: Scarabaeidae

2. Pest description

• Adults: Beetles of 8–12 mm; metallic copper-green body; coppery-brown elytra; five tufts of white hairs on each side of the abdomen and two at the posterior end, a distinctive feature of the species.
• Larvae: Whitish “C”-shaped bodies with a brown head; typical beetle larvae (white grubs); develop in the soil feeding on roots.
• Pupae: Formed in the soil, yellowish to brown in colour.
• Eggs: Laid in the soil, in moist, vegetated areas.

3. Main hosts

• Highly polyphagous species, with more than 300 recorded hosts.
• Agricultural crops: maize, soybean, bean, strawberry, raspberry, grapevine, potato, tomato.
• Trees and ornamentals: linden, birch, maple, rose, apple tree, pear tree, chestnut tree.
• Meadows and lawns: larvae feed on the roots of grasses.

4. Symptoms and damage

• Adults feed on the leaves, leaving them skeletonised due to the removal of the tissue between veins.
• Damage to flowers and fruits, reducing their commercial value.
• Larvae cause root damage, leading to yellowish patches and drying in lawns and pastures.
• Reduced plant vigour and greater susceptibility to water stress.
• In severe infestations, it can cause significant losses in agricultural and ornamental crops.

5. Biological cycle

• One annual generation in temperate climates; two in warmer regions.
• Adults emerge in summer and feed intensively for 4–6 weeks.
• Egg-laying in the soil; larvae develop feeding on roots until autumn.
• Larvae overwinter in the soil and resume activity in spring.
• Pupation in late spring, with adults emerging in early summer.
• Development favoured by moist soils, mild temperatures and a high availability of hosts.

6. Monitoring

• Observation of skeletonised leaves and damage to flowers.
• Visual inspection of adults in aggregations, especially on hot, sunny days.
• Assessment of lawns to detect larvae (yellowish patches, turf that lifts easily).
• Traps with pheromones and kairomones for early detection and population tracking.
• Reinforced monitoring in areas with confirmed presence of the pest (quarantine species in the EU).

7. Management measures

• Cultural: Manual removal of adults in small areas; maintenance of healthy lawns; reduction of excessive irrigation that favours egg-laying.
• Preventive: Avoiding the transport of soil, plants or turf from infested areas; strict phytosanitary surveillance.
• Integrated protection: Use of traps only for monitoring; intervention only when necessary; practices that reduce the attractiveness of the habitat; coordination with phytosanitary authorities due to the quarantine pest status.

Bibliographic references

• CABI Invasive Species Compendium – Popillia japonica.
• EPPO Global Database – Popillia japonica.
• USDA APHIS – Japanese beetle biology and management.
• Potter, D. A. (1998). Destructive turfgrass insects: biology, diagnosis, and control.