Insect pest risk

High riskReduced riskLow risk
Earth Mites
Canola sown into paddocks coming out of pastures.Intensive grazing reduces survival of mites in pasture.Rotation with non-crop hosts (e.g. lentil, chickpea, wheat, barley, lupins and linseed) will reduce the size of mite populations in a paddock. Non crop host must be weed-free.
Lucerne Flea
  • History of Lucerne Flea.
  • Loamy, clay soils.
  • Weedy fallow or pasture with no LF control.
Intensive grazing reduces carry-over. Cultivation can reduce oversummering eggs.
Weedy fallows or weeds in proximity to seedling crops.

Spraying out weeds with large cutworm larvae that then move onto establishing crop.

Controlling weed hosts at least 2 weeks prior to crop emergence.
Diamond back moth
  • High summer rainfall creating brassica green bridge
  • Warm and dry conditions July through spring
  • No significant rainfall events (>10 mm)
  • Significant heavy rainfall (>10 mm) (will dislodge and drown larvae)
  • High beneficial activity and/or DBM parasitism


  • Cool moist conditions late winter through spring
  • Epizootics of fungal disease (e.g. Zoopthera radicans)
  • Weedy crop edges and neighbouring fields with brassica weeds (wild radish, wild turnip, capeweed).
  • Above average rainfall in autumn promotes weed growth.
  • Use of broadspectrum insecticides will kill natural enemies that may suppress populations.
Drought stress increases impact of aphids by increasing the rate of aphid population growth and reducing the crop’s ability to compensate for flower and pod abortion
  • Early sowing so crop flowers in early spring – before aphid populations peak
  • Cold, wet conditions in winter suppress populations
  • High in-season rainfall can suppress populations and promote the outbreak of diseases
  • Soft chemicals (pirimicarb, PSOs) that preserve beneficials that may control survivors.
Native budworm (Helicoverpa punctigera)
  • Wet winters in breeding areas of central Australia + suitable weather conditions facilitates spring migrations
  • Repeated influxes of moths over long periods means reinfestation can occur post-treatment
  • Hot spring weather can cause small larvae to burrow into pods
  • Broadleaf weeds can host large numbers which can move into crops as medium-large larvae and rapidly damage pods
  • Treating aphids and DBM with broadspectrum insecticides can disrupt beneficials that may suppress outbreaks
Dry winters in breeding areas contribute to a low population source and the absence of migration opportunities.
Slugs and snails
  • Annual rainfall >500 mm
  • Above average spring – autumn rainfall
  • No till stubble retained
  • Previous paddock history of slugs and snails
  • Summer volunteers and weeds
  • No sheep in enterprise
  • 450-500 mm annual rainfall
  • Tillage or burnt only
  • Sheep on stubble
  • <450 mm annual rainfall
  • Drought
  • Tillage and burnt stubbles
  • No volunteers and weeds
Other pests
Late sowing into cold soil reduces plant growth and increases vulnerability to insects and slugs.
  • Cultivation in autumn destroys the potential habitat and food source of many pests.
  • Early sown crops

Pest incidence

Economic damage from insect pests is most likely to occur during establishment and from flowering until maturity.  Major pests are in bold.

Rutherglen bug is best known as a seed-feeding pest, attacking grain as it develops and fills. However, in some seasons, large numbers of nymphs and adults can cause damage to establishing winter or summer crops. RGB populations can build up in summer weeds, and move from these into establishing winter crop, feeding on and killing small seedlings. Large numbers of RGB moving out of canola stubble pose a threat to nearby establishing summer crops.

PestCrop stage






Lucerne fleaDamagingPresent
False wirewormDamaging
Slugs and snails*DamagingDamaging
Rutherglen bugDamagingDamagingDamagingDamaging
Diamond back moth (DBM)DamagingDamagingDamagingDamaging
Helicoverpa punctigeraPresentDamagingDamagingDamaging
Helicoverpa armigera (NOT IN WA)PresentDamagingDamagingDamaging
* Snails may also cause grain contamination at harvest
**Early colonisation by virus infected aphids
PresentPresent in crop but gen­er­ally not dam­ag­ing
Dam­ag­ingCrop sus­cep­ti­ble to dam­age and loss

Key IPM considerations for canola

  • Monitor regularly and record pest and beneficial numbers. Review checking data for population trends.
  • Tolerate early damage. Canola can compensate for early damage by setting new buds and pods to replace those damaged by pests. Excessive early damage may reduce yield.
  • Biopesticides used in vegetative canola prior to flowering will preserve beneficials
    • NPV is effective against Helicoverpa larvae less than 7 mm long
    • Bt is effective against DBM and Helicoverpa (less than 7 mm long)
  • Consider the use of spray oils where aphid populations are low to moderate (repeat applications required).
  • Where pests invade from adjacent fields consider spraying only borders and not the whole field
  • Control some pests e.g. lucerne flea or mites in preceding pasture or broadleaf crops.
  • Use aphid-selective products e.g. pirimicarb to preserve the beneficial insects; potentially reducing the need for follow-up applications.
  • Seed dressings may be the most effective control for some soil insects, as well as the least disruptive to natural enemies
  • Consider cultural control or biological control methods

Insecticide choices

  • RLEM and BOM can occur in mixed populations. There is evidence that RLEM and BOM species have different susceptibilities to chemicals. Determine species composition before making spray decisions.
  • Pest populations are often affected by competition from other pests within farming systems. E.g. applying chemicals with specific activity against red legged earth mite (e.g. bifenthrin) can lead to a substantial increase in lucerne flea numbers through the removal of competition.
  • Increasing pesticide usage to control RLEM may not solve pest problems but select for pests that are more difficult to kill e.g. Balaustium mites.

Insecticide resistance

  • RLEM has been found to have high levels of resistance to two synthetic pyrethroids – bifenthrin and alpha-cypermethrin. This resistance has been found to have a genetic basis, persisting after several generations of culturing in the laboratory
  • Some BOM tolerance to registered rates of insecticides in Northern NSW
  • Resistance found to SPs in DBM, H. armigera and green peach aphid
  • Green peach aphid has variable resistance to pirimicarb in WA, and potentially to SPs and OPs nationally

Further information

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