Plum curculio

Conotrachelus nenuphar

1. Identification

• Common name: Plum curculio
• Scientific name: Conotrachelus nenuphar Herbst
• Order: Coleoptera
• Family: Curculionidae

2. Description of the pest

• Adults: Weevils of 4–6 mm, dark brown body with fine scales and a short rostrum; they move actively in the crown during spring.
• Larvae: Apodous, whitish, with a curved body and brown head; they develop inside the fruits, feeding on the pulp and the seeds.
• Pupae: Formed in the soil, in earthen chambers.
• Eggs: Deposited in young fruits, through small incisions made by the adult.

3. Main hosts

• Plum, peach, apricot and other species of Prunus.
• It may also attack cherry and other fruiting rosaceous plants, although less frequently.

4. Symptoms and damage

• Oviposition borings in young fruits, frequently accompanied by gum exudation.
• Premature fall of fruits due to internal larval development.
• Deformed fruits, with internal galleries and destroyed pulp.
• Significant reduction of commercial production, especially in young or poorly monitored orchards.
• In severe attacks, it may compromise the entire harvest.

5. Biological cycle

• One generation per year in temperate climates, with two possibly occurring in warmer regions.
• Adults emerge in spring and feed on buds and young fruits before egg-laying.
• Eggs deposited in the fruits; larvae develop inside for 2–3 weeks.
• Larvae abandon the fruits and bury themselves in the soil for pupation.
• Adults overwinter in the soil or under plant debris, emerging the following spring.

6. Monitoring

• Observation of oviposition borings and gummy exudation in young fruits.
• Counting of prematurely fallen fruits, especially in early summer.
• Internal inspection of suspect fruits to detect larvae.
• Reinforced monitoring in orchards with a history of the pest.
• Traps with food attractants may be used to detect adults.

7. Management measures

• Cultural: Removal and destruction of fallen fruits; surface tillage of the soil to expose pupae; maintenance of clean orchards.
• Preventive: Prunings that favour air circulation; reduction of shelter sources for overwintering adults; selection of less susceptible varieties when possible.
• Integrated protection: Regular monitoring; intervention only when necessary; practices that reduce the survival of larvae and pupae in the soil; attention to the legal framework, given that C. nenuphar is considered a quarantine pest in several regions and is included in phytosanitary surveillance lists under Regulation (EU) 2016/2031 and Implementing Regulation (EU) 2019/2072.

Bibliographic references

• EPPO Global Database – Conotrachelus nenuphar.
• CABI Invasive Species Compendium – Conotrachelus nenuphar.
• European Commission – Regulation (EU) 2016/2031 on protection against quarantine pests.
• European Commission – Implementing Regulation (EU) 2019/2072.
• EFSA – Scientific Opinions on stone fruit pests.
• USDA – Plum curculio management guidelines.