Crown Borers

Biology

Strawberry crown borers are flightless snout beetles. The adults are small (about 4 mm long), dark-brown to black, beetles. They have 3 darker spots on each wing cover. Their larvae have the appearance of small, white grubs (curved body, with 3 pairs of legs).

Symptoms of Damage

Damage is caused by the larvae boring and feeding in the crown of the plant. The crown may be hollowed out and stained a reddish brown colour. The adult crown borers may eat small holes in the leaves and feed off the crowns, creating cavities where eggs are deposited. Weakened plants may be attached by other insects or by disease.

Feeding produces many small, round holes (about 6 mm in diameter) on the leaves. Economic injury results from larvae feeding in the crowns of the plants. Affected plants show abnormal red pigmentation in the leaves.

Monitoring

Inspect strawberry plants along the field borders for the presence of wilted or dead plants, beginning when blossoming starts. Check inside the crowns of these plants for the presence of one or two borer larvae in the hollowed out area.

Economic Thresholds

No economic thresholds have been developed for this pest.

Comments

Crop rotation helps reduce populations of this pest because the flightless beetles can only migrate by crawling. Avoid placing new plantings closer than 300 m to old plantings or to fields containing wild strawberries or cinquefoil. Deep ploughing and compacting the soil after the final crop is harvested will destroy many crown borers. Destroy strawberry refuse from old fields after harvest.