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Grey-banded leaf weevil

Grower, Bronwyn Hunt, reported weevils causing extensive feeding damage to emerging canola seedlings in several paddocks near Kerang, in the Mallee district of Victoria. They have been identified by Senior Technical Officer, Ken Henry (SARDI), as the grey-banded leaf weevil (Ethemaia sellata). Bronwyn says the weevils had chewed scalloped pieces out of cotyledons and in some cases, completely removed the top part of canola seedlings. The affected paddocks contain quite a lot of trash, which may be aiding their survival.

Adults are approximately 8 mm long, grey in colour with distinctive raised markings (bumps) and a white area on the bottom covering approximately 1/4 of the wing covers (elytra). Adults are thought to be flightless. Eggs are laid on plant leaves and pupation occurs in the soil. Larvae are often confused with vegetable weevil larvae, which are similar in size and colour.

Little is currently known about the feeding ecology of grey-banded leaf weevils. It is thought that they may surface feed on malvaceous weeds (e.g. marshmallow weed) and some ornamental plants, and these could be the source of infestations in crops. This species has been recorded as common in gardens, and both adults and larvae are known to attack several ground vegetables. They may also be a grain contaminant at harvest. Bronwyn says there is marshmallow weed in most paddocks and that weevils can be quite easily found feeding directly on the leaves.

Crops should be monitored closely, particularly near fence-lines, as adults tend to move into crops from host weeds and scrub. There are no insecticides currently registered to control grey-banded leaf weevils. However, when synthetic pyrethroids have been used at 400mL/ha against other pests, they are reported to provide adequate control. Bronwyn says that canola paddocks sown with insecticide-treated seed experienced far less feeding damage from weevils.

Click here for images of the grey-banded leaf weevil.

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