Canola - Insect threshold levels

Pest Control threshold

Sampling recommendation

Additional notes

Mites: Redlegged earthmite (RLEM)

Balaustium mite (BOM)

Clover mite

If more than 50% of cotyledons are bleached white and the first true leaf is also being damaged apply control. 10 mites per 100cm²

Estimate the number of mites/100cm (10 x 10 cm) around the base of the plant (on weeds, soil and seedlings). Repeat at 5 – 10 sites. Avoid sampling in bright light, sample on cloudy days, early morning or late afternoon.

RLEM and BOM can occur in mixed populations. The two species have different susceptibilities to chemical sprays. Determine the species composition of the population before making spray decisions


More commonly Green peach aphid, Cabbage aphid and Turnip aphid

At least 20 % of plants with 25 mm, or more stem infested. Moisture stresses seedlings not able to compensate for damage

Sample crops twice weekly during flowering and podding. Inspect crops regularly through winter and early spring

Always determine the level of natural enemy activity when making control decisions about aphids. Early aphid infestations are of greater significance on terms of potential damage

Caterpillars: Cutworm

2-3 cutworm/m²

Early detection of larvae or plant damage essentail. Examine plants, old litter and soil surface in 0.5 m of row. repeat at 5 - 10 sites

Autumn - winter active

Caterpillars: Brown pasture looper

10 - 12 loopers/m²

On crop and weeds especially capeweed


Caterpillars: Diamondback moth

1 caterpillar per canola seedling can cause crop damage

On leaves and when touched fall down on silk thread.


Caterpillars: Cabbage moth

Only count caterpillars longer than 3 - 4 mm

Mid to late flowering: 17 - 23 / 10 plants

Pod maturation: 43 - 57 / 10 plants. Walk through the crop in a circular pattern. Start 10 - 15 m in from crop edge. Stop at 20 - 25 m intervals and randomly select a plant. Pull trhe plant up and shake into a sweep net (fold larger plants in half to shake). Count cabbage moth larvae longer than 3 - 4mm

Rainfalls greater than 5 - 8 mm in 24 hours will reduce the number of larve in the crop. If populations are approaching the threshold prior to such rainfall, sample again before making a decision to spray

Lucerne flea

Ave. 10 holes/leaf at 5-10 sites are observed

Inspect 0.5 m of crop row. Look for characteristic holes in leaves



False wireworms

Bronze field beetle

5 of more adults per m² can produce damaging numbers of larvae

Under crop residues close to soil surface especially around plants

Inspect paddocks in spring into which canola will be sown the following season

Beetles: Vegetable beetle

1 beetle per canola seedling

On ground in close proximity to seedling




Desiantha weevil

Fuller's rose weevil

Small lucerne weevil

Vegetable weevil

5 weevils per m²

Adult weevils hide under surface debris during the day. Vegetable weevil larvae can be found in growing points, leaf axils and under leaves


Rutherglen bug

5 or more nymphs per canola seedling at the cotyledon or 2 leaf stage

Inspect canola crops regularly from flowering to windrowing. Inspect heads visually, or by shaking into a bucket. Examine 20 heads

Repeat at 5 - 10 sites

Rutherglen bugs move into crops as host weeds, e.g. capeweed

European earwig

1 earwig per canola seedling can cause extensive crop damage

On plants at night or hidden under clods, trash or objects by day


Slaters: Various species

Seedlings not able to out-grow damage

Found at base of seedlings at night or under stubble, dead organic matter by day



Black keeled slug

Reticulated slug

1 or more slugs per m²

Detect incidence early in the season using shelter traps e.g. moist hessian bags laid on the soil


Pointed snails

Pointed snails = 20 per m²

A management plan for the year starting soon after harvest is needed to avoid damage and contaimination


White Italian snails

Vineyard snails

White Italian snail and Vineyard snail - 5 per m²

A management plan for the year starting soon after harvest is needed to avoid damage and contaimination

Page last updated: Friday, 17 April 2015 - 11:45am