Diagnosing native budworm in canola

The native budworm caterpillar can cause serious yield loss to canola as pods mature.

 Caterpillar up to 40 millimetres long usually with a dark streak along its body
They drill through the pod wall and eat the seeds.

What to look for

    Insect Larvae

  • Caterpillars up to 40mm long that are shades of orange, brown and green and usually have a dark stripe along its body.
    Caterpillars feed on leaves and stem until the crop nears maturity, then they are attracted to the pods. They drill through the pod wall and eat the seeds.

    Insect Adult

  • Native budworm will also continue to damage seed pods if the crop has been swathed when many pods are still green with soft seed or if drying of the swath is prolonged due to wet weather.

What else could it be

Condition Similarities Differences
Diagnosing diamondback moth Small caterpillars look very similar Diamondback moth caterpillar are smaller,green, cigar shaped and graze the pod surface without entering the pod.
Diagnosing cabbage white butterfly Green caterpillar eating holes in leaves Velvety green caterpillar that is uncommon and rarely eats floral parts.

Where did it come from?

  • The native budworm can develop large populations over extensive areas on native plants. These populations often migrate into agricultural regions in late winter and spring.
  • Migratory flights are unpredictable, as moths are carried hundreds of kilometres from breeding areas by high altitude currents.

Management strategies

  • The decision to spray for native budworm in canola and lupins (but not other crops) can be left until pods are beginning to mature. If caterpillar numbers are below threshold limits, the decision to spray should be delayed and periodic sampling continued.
  • Threshold for control in canola and lupins (but not other crops) is six or more grubs per 10 sweeps at pod maturation. This threshold varies with grain price and control costs see 'See Also' section for more information.
  • One well timed spray to control caterpillar populations is all that is required in most situations.

How can it be monitored?

  • It is essential to determine native budworm numbers by sampling crops using a sweep net because in dense canola crops the grubs are very difficult to detect.
  • Begin monitoring at flowering.

Where to go for expert help

Page last updated: Monday, 1 May 2017 - 11:47am