Diagnosing vegetable beetle damage

A widespread beetle is mainly a pest of summer crops, but has seriously damaged young canola in southern districts, especially when there has been a warm start to the growing season. Vegetable beetles are not to be confused with vegetable weevils that have a long snout.

What to look for

Paddock

Patches of dead and chewed seedling to 5 leaf canola plants.
Areas near rock heaps or with heavier stubble or previous pasture residues may be more affected.
As the beetles are most active above 15 °C, early sown paddocks will be more affected.

Plant

Plants dead and ringbarked or chewed crown, stem or petiole.

Insect Adult

Oval 8 millimetres (mm) long beetles with a rounded head and flattened body. They are usually a dull grey colour, but may appear brown or almost black.
Vegetable beetles are not to be confused with vegetable weevils that have a long snout.
They generally hide under rocks and plant residues during the day but may come out to feed in warm weather. They are easily found in close proximity to damaged plants.
Beetle larvae (yellow shiny hard shelled false wireworms), may be present just beneath the soil surface, but rarely damage canola.

Management strategies

Vegetable beetles tolerate high insecticide rates, and there are currently none registered for their control.
Main risk factors are: Southern district crops, high amounts of retained stubble and early sown crops when temperatures are above 15°C.
Beetle numbers can be decreased by reducing shelter such as stubble or rocky out-crops under which beetles can survive the summer.
Increased seeding rate helps maintain plant density in high risk years, or if reseeding is required.

How can it be monitored?

Monitor canola crops for damage from seeding, especially if there is a warm start to the season.