Notes on Apple Insects
Plum curculio
Identification
Plum curculio (PC) is a native beetle and a major pest of pome and stone
fruit in Ontario. Adult beetles are 4-6 mm long, dark brown with grey
and white patches on the back. Adults have distinctive humps on their
wing covers, as well as a distinctive elongated beak-like snout.
Early in the season PC feed on flowers and developing fruitlets, creating
small irregular feeding holes. Females lay eggs in developing fruit and
cause small crescent shaped scars. The summer generation of adults feed
on growing fruit by excavating small holes and feeding on the pulp.
Period of activity
Plum curculio are first seen in orchards from pink through petal fall.
Adults move into the orchard from nearby overwintering sites, such as
brush piles or leaf debris, after several days of warm temperatures and
rain. These insects remain in the orchard until late September then migrate
out in search of suitable overwintering sites.
Monitoring and thresholds
Traps that attract PC by sight or smell are not effective for evaluating
potential damage from this pest. From bloom through petal fall, check
fruit on wild fruit trees near the orchard for PC feeding and oviposition
scars. Carefully check for PC damage in orchard border rows near woodlots
and wild hosts. Apply an insecticide at first sign of injury.
Management notes
Border sprays are effective to manage this pest, unless there is a history
of problems with PC. Adults move into the orchard over a three to six
week period and actively lay eggs for over a month. Therefore, continue
to monitor for the pest and any new damage throughout this period.
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