PEST
 
   NAME
     Argentine Stem Weevil
     Listronotus bonariensis
 
   ORDER
     Coleoptera
 
   FAMILY
     Curculionidae

Description of the Pest
The small adult is a striped dark grey-brown weevil up to 3mm long and is capable of flying. They are not commonly seen and the tiny legless lava feed on stems and roots.  Both adult and larvae have chewing mouth parts. This pest was formally known as Hyperodes bonariensis.

 Adult feeding on a leaf blade

Life Cycle
This insect has a Holometabolous life cycle, i.e. it has a larval and a pupal stage.
The eggs are deposited in the leaf sheath of grass species and the lava tunnel into the stems then fall to the ground to feed on the roots and to pupate. Emerging adults fly to a new host plant.

Distribution of the Pest
The weevils are active from spring to summer with more generations produced in warmer areas. It is found throughout Australia, South America and New Zealand from sub tropical and temperate regions. 

Period of Activity
The insects are active from early spring to late autumn but in warm climates they may be seen throughout the year.

Damage Caused
Patches of lawn appear yellow and to be dry or dead as the pest severs the roots and damaged areas don’t respond to watering and may be easily lifted out. The characteristic damage to the leaves by the adults is that of 3mm rectangular clear areas on the leaves.

Susceptible Plants
This weevil attacks cool season turf such as Bent and Rye species. It also attacks wheat, maze and barley.

Control

Cultural Control
It is difficult to control and less susceptible species could be planted. 

Biological Control
No effective biological control. Available in Australia at the moment though success has been achieved in New Zealand with a parasitic wasp (Microctonus hyperoda) and a fungal pathogen (Beauveria bassiana)
A nematode is being researched in Australia

Chemical Control
Infected areas may be sprayed with contact insecticide and a wetting agent.  Granular formulations can also be used.

Note
It is your responsibility by law to read & follow the directions on the label of any pesticide
Monitoring
Drench a known area with a suitable insecticide and count the number of adults emerging for at least 10 minutes. If 3 or more per square metre for Poa species or around 6 per square metre for bent greens then controls may need to be implemented
Amendments by B. Sonsie Dip Hort Sc Burnley