- Scalloped leaf damage.
Photo: Southern ute guide
- Adult sitona weevil. Photo: Southern ute guide
Larvae are up to 5 mm long, white-cream with an orange brown head, legless and have a slightly curved body. Adults are 5 mm long and are greyish-brown with three yellowish-white stripes behind the head and a short broad snout.
Native to the Mediterranean region, now present in Europe, North Africa, South Africa, Australia and New Zealand.
Major in South Australia, minor in New South Wales, Tasmania and Victoria, restricted and irregular.
Lucerne, annual medics, subterranean clover.
Larvae feed within or on the root nodules and can cause more serious damage than adults by reducing nitrogen fixation and retarding plant growth. Older larvae feed on lateral and taproots. Adults make scallop-shaped notches along leaf margins and also chew the stems of seedlings and older plants.
Damage is most severe in spring and autumn.
Eggs are laid in autumn in the soil around the base of plants and hatch with opening rains, when the emerging larvae burrow into the soil. Larvae feed through the winter and early spring to pupate in the soil and emerge as adults in late spring/early summer.
Inspect pastures for signs of seedling damage by adult weevils.
If adults are in large numbers and killing seedlings in autumn, chemical control may be required.
Natural enemies: A sitona weevil parasitoid, Microctonus aethiopoides, was introduced to Australia as a biological control agent from the Mediterranean area. The parasitoid lays a single egg in the weevil´s body causing sterilisation and eventual death of the weevil.
- Pests of field crops and pastures: identification and control, editor P T Bailey.