Argentine Stem Weevil

Argentine Stem Weevil (Listronotus bonariensis) like other weevils is distinguishable from beetles by their long snouts and their legless grubs or larvae. Adults are small being approximately 5-10mm long and greyish brown in colour whilst the larvae are creamy white. This is mainly a pest of ryegrass in particular with the larvae feeding within the grass stem whilst the adults feed on expanded leaves.

The damage caused by adults in particular is noticeable by the windows they chew in the leaves. Damage from Argentine Stem Weevil can occur throughout the warmer months from September through until late April.

These are difficult to kill using insecticides. Cultivation prior to sowing has shown to provide a reasonable level of control in areas where numbers of stem weevils have traditionally been high. Most ryegrasses now incorporate an edophyte which is a fungus that protects the plants from Argentine Stem Weevil.