Argentine stem weevil (ASW) (Listronotus bonariensis) were first recognised as a pest in New Zealand in 1933 and is now regarded as one of the country’s major insect pests. Both the adult and larval stages feed on a wide range of cereal host plants as well as grasses and maize. ASW is considered a pest throughout New Zealand.
Key points
- Argentine stem weevil (ASW) occurs throughout New Zealand and is a pest of seedling maize.
- Damage is caused by ASW larvae, and peak larval numbers coincide with spring maize planting.
- Maize sown after pasture, annual ryegrass or cereal crops, or into areas with lots of grass weeds, is likely to suffer ASW damage.
- Damage is characterised by the centre leaf of the seedling wilting and turning grey-green in colour. Close observation will reveal a pin head sized hole at the base of the plant.
- Cultural control can be achieved by a six-week physical or chemical fallow period.
- Insecticide seed treatments generally provide good control.