Bronzed Field Beetle
Caterpillar - Dark brown larvae up to 12 mm long with upturned spines on its tail.
Colour - Dark brown
Body - Up to 12 mm ling
Abdomen - Has upturned spines
Prefers high trash or stubble retention areas. The larvae are usually found under trash near plants it is feeding on, or in the soil close to the surface.
Damage signsPlant stems are chewed at ground level, weakening or killing plants.
Origin and History:Distribution:
Pest of seedling Canola and Lupins.
Management and Control:Bronze Field Beetle has a larval stage that is also called the false wireworm. It tends to feed on the surface whereas the Vegetable Beetle False Wireworm tends to feed below the soil surface. The False Wireworm of the Bronze Field Beetle appears to be more difficult to control and rates of 300 mL/ha of Dominex or Fastac are required. They appear to build up in zero till and stubble retention crop systems especially on header or swath rows and can be very damaging to Lupins and Canola. Raking and/or burning the stubble provide high levels of control. In trials, raking the stubble has reduced numbers of adults by 99.9% compared to 95% control with 2 sprays after planting. Cosmos as a seed dressing and to a lesser extent Confidor have shown promise in trial work (P. Michael, 1999).
To reduce the impact of Bronze Field Beetle and it larvae in Canola and Lupin paddocks;
1) reduce the trash level,
2) lay a carpet square on the ground in autumn to determine the level of infestation,
3) if it is high, treat seed with Cosmos, Confidor or Lorsban
4) increase crop seeding rate
5) Spray with 300 mL/ha Dominex 100 (or equivalent synthetic pyrethroid) around emergence of the crop, if damage is still occurring. Repeat in 10-14 days if necessary.
Thresholds:Young Canola - probably around 50 per square metre for Grey False Wireworm and 25 per square metre for Large False Wireworm.
Dig 10 soil samples 32 cm by 32 cm and 2 cm deep to get the larvae per square metre before planting.
Inspect potential Canola and Pulse paddocks in the spring before planting because larvae are easier to find in spring.
Related Species:Vegetable Beetle or False wireworm.
CSIRO. The Insects of Australia. Melbourne University Press. (1991)
WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185.
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