Vegetable beetle can spell trouble for canola (and cereals)

Adult vegetable beetles lay their eggs in autumn and their larvae can pose problems in cereals.

Vegetable beetle, aka southern false wireworm (Gonocephalum spp.), are native to Australia and generally feed on decaying organic matter. However, it is not uncommon for the adults to feed on emerging winter canola, chewing plants above ground, ring barking or completely cutting stems. Vegetable beetle adults are 6 – 8 mm long and 3 mm wide, matte dark grey-black in colour and often mottled or covered in soil. While the beetle can persist throughout the year, they become less of an issue in canola as the crop gets away from the vulnerable establishment phase.  

Vegetable beetles are found throughout Victoria and New South Wales. They can be a substantial pest in south-west Victoria, mostly on canola. Outside of the South West, this autumn vegetable beetles have been reported causing issues near Boort and Avoca in North Central Victoria.

The larvae hatching from eggs laid in autumn can spell trouble for cereal crops during the colder winter months. Vegetable beetle larvae are soil dwelling and attack winter cereal crops by boring into germinating seeds, or chewing on seedling roots and shoots. The larvae tend to feed exclusively below the soil surface. Larvae typically grow to about 18 – 20 mm long, and are hard-bodied and shiny in appearance with a body colour that is cream-yellow or tan. They have hard, cylindrical and elongated bodies with 6 legs. They lack the two spines that are obvious on the final segment of many other false wireworm larvae. 

Vegetable beetle/southern false wireworm larvae (Source: SARDI)

Adult vegetable beetle/southern false wireworm (Source: cesar)

 

Control options are limited for vegetable beetle larvae post-sowing due to their subterranean feeding habits and high tolerance level to insecticides. If you identify paddocks prone to vegetable beetle damage, consider an integrated approach to control next year by incorporating a combination of the following:

- Raking and/or burning stubble

- Cultivation

- Sowing a pulse crop

- Increasing the canola seeding rate

For more information on vegetable beetles including their occurrence, lifecycle, behaviour and management strategies, visit southern false wireworm within our PestNote series.

 

Field reports

Matthew Cain – IK Caldwell (North Central, VIC)

Craig Muir – AGRIvision (Mallee, VIC)

Alistair Tippet – Landmark (Central, VIC)