Notes on Raspberry Insects: Raspberry Crown Borer

Identification

Affected canes wither and die or growth is limited and fruit is small. Eventually, primocanes become so few in number that the planting dies out.

Mature raspberry crown borer larvae are 2.5 cm, cream coloured larvae with brown heads and obvious legs. The adult is a clear-winged moth with a wingspan of 2.5-3.0 cm. The yellow bands across its black abdomen cause it to resemble a yellow jacket wasp.

Crown borer larvae

Raspberry crown borer larvae close-up

Raspberry crown borer larvae

Raspberry crown borer larvae

Period of Activity

The adult lays its eggs on plant foliage in summer; larvae travel to the base of the cane to overwinter. They tunnel into the cane and crown the next spring. Larvae spend two years in the crown and root area before they emerge as adults. They burrow at the base of the cane, in larger roots and in the crown. Around harvest time of the second summer, they pupate and emerge from the crown.

Monitoring

  • To diagnose this pest dig up crowns and look for larvae, sawdust-like frass and tunnels. Cut through the crown with clippers or shears to look for larvae.
  • Canes that grow out of infested crowns can sometimes be pulled or tugged away from the crown to reveal borer damage and frass.

Management notes

Insecticides are targeted at the base of the cane in fall or early spring before the larvae tunnel in. Treatment is required for two years to break the cycle of this pest.

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