Grey-banded leaf weevil

Agronomist, Andrew Parr (Howard Martin & Co), reports finding high numbers of grey-banded leaf weevils (Ethemaia sellata) attacking several emerging canola crops around Berrigan, in the Riverina district of New South Wales. The weevils have been found in or near paddocks where marshmallow weed was present over summer and has recently been sprayed out. In the worst affected areas, Andrew reports finding 10 weevils in half a metre of crop row, and says damage is evident across the paddock (scalloping and chewed leaf margins). The paddocks affected were all cereal crops last season.

Adult grey-banded leaf weevils are approximately 8 mm long, light brown-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. Larvae are yellow to green in colour with a light green-brown head capsule. They are legless, grow to approximately 5-8 mm in length, and are often confused with vegetable weevil larvae, which are similar in size and colour. Click here for images of grey-banded leaf weevils.

Little is known about the feeding ecology of grey-banded leaf weevils. Adults are known to attack several winter crops including canola and lupins, and they may also be a grain contaminant at harvest. They are closely associated with malvaceous weeds (particularly marshmallow) and this has often been found to be the source of infestations in crops. Paddocks should be monitored near fence-lines and where there have been large areas of summer weeds. 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. Previous reports also suggest that canola paddocks sown with insecticide-treated seed experience less feeding damage from weevils.