Insect pest risk

High risk Reduced risk Low risk
Earth mites
Paddocks rotated out of pastures. Intensively grazed pasture (reduces mite survival). Rotation with weed-free non-crop hosts reduces mite populations. Non-host examples: lentil, chickpea, wheat, barley, lupins, and linseed.
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 over-summering eggs.
Cutworm
  • Weedy fallows or weeds in proximity to seedling crops.
  • Spraying out weeds with large cutworm larvae that then move onto establishing crop.
 Weed hosts controlled at least 2 weeks prior to crop emergence.
Diamondback moth (also known as cabbage moth)
  • High summer rainfall (creates 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).
Aphids
  • Weedy crop edges and/or neighbouring fields with brassica weeds (wild radish, wild turnip, capeweed).
  • Above average rainfall in autumn (promotes weed growth).
  • Use of broadspectrum insecticides (kill natural enemies that may suppress populations).
 Drought stress increases aphid population growth rate and reduces the crop’s ability to compensate for flower and pod abortion.
  • Early sowing (crop flowers before aphid populations peak).
  • Cold, wet winter (suppresses populations).
  • High in-season rainfall (can suppress populations and promote the outbreak of aphid pathogens).
  • Soft chemicals (pirimicarb, spray oils) that preserve beneficials that then may control survivors.
Native budworm (Helicoverpa punctigera)
  • Wet winters in breeding areas of central Australia + suitable weather conditions for spring migrations.
  • Repeated influxes of moths over long periods means reinfestation can occur post-treatment.
  • Hot spring weather (small larvae may 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 only or burnt sutbble only.
  • Sheep on stubble.
  • <450 mm annual rainfall.
  • Drought.
  • Tillage and burnt stubble.
  • No volunteers and weeds.
Other pests
Late sowing into cold soil reduces plant growth and increases vulnerability to insects and slugs.
  • Autumn cultivation (destroys pest habitat and food source).
  • 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 crops. RGB populations can build up in summer weeds, and move into the establishing winter crop, feeding on and killing small seedlings. Large numbers of RGB moving out of canola stubble also pose a threat to nearby establishing summer crops.

Pest Crop stage

Emergence

Vegetative

Flowering

Podding

Grainfill
Mites Damaging Present
Lucerne flea Damaging Present
Cutworms Damaging Present
False wireworm Damaging
Cockchafer Damaging
Slugs and snails* Damaging Damaging
Rutherglen bug Damaging Damaging Damaging Damaging
Aphids Damaging** Damaging Damaging Damaging Present
Diamondback moth Damaging Damaging Damaging Damaging
Helicoverpa punctigera Present Damaging Damaging Damaging
Helicoverpa armigera (NOT IN WA) Present Damaging Damaging Damaging
* Snails may also cause grain contamination at harvest
**Early colonisation by virus infected aphids
Present Present in crop but gen­er­ally not dam­ag­ing
Dam­ag­ing Crop sus­cep­ti­ble to dam­age and loss

Key IPM considerations for canola

  • Monitor regularly, recording both pest and beneficial numbers. Review checking data for population trends.
  • Tolerate low-moderate early damage, as canola can compensate by setting new buds and pods if sufficient growing time remains.
  • Biopesticides used in vegetative canola prior to flowering will preserve beneficials:
    • NPV is effective against Helicoverpa (less than 7 mm)
    • Bt is effective against Helicoverpa (less than 7 mm) and diamondback moth.
  • 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 rather than the whole field.
  • Control some pests (e.g. lucerne flea or mites) in preceding pasture or broadleaf crops.
  • Use selective products when spraying for aphids (e.g. pirimicarb) to preserve beneficial insects.
  • Seed dressings may be the most effective control for some soil insects, as well as the least disruptive to natural enemies.

Insecticide choices

  • Earth mites 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 regulated by competition from other pests within farming systems. For example, 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. See the RLEM Resistance Management Strategy for more information.
  • Some BOM tolerance to registered rates of insecticides in Northern NSW.
  • Resistance found to synthetic pyrethroids in DBM, H. armigera and green peach aphid.
  • Green peach aphid has variable resistance to pirimicarb in WA, and potentially to synthetic pyrethroids and organophosphates nationally. See the GPA Resistance Management Strategy for more information.

Further information

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