PestFacts WA

Identifying and managing weevils in canola

  • Mingenew
  • Wandering
  • South Stirlings
  • Ongerup
  • Gairdner
  • Gnowellen

Geoff Fosbery (ConsultAg) reports that weevils are causing widespread damage to a seedling canola crop north of Mingenew.  The identity of the weevils is unknown and samples are being sent to DPIRD entomologists for identification.  A nearby property was inspected by Nick Eyres (Elders) who found similar damage caused by weevils. The weevils had survived insecticides that was applied post sowing and emerged to feed on the canola, causing high levels of damage, in some cases. Images sent in resemble a weevil previously reported from crops between Dongara and Mingenew, which entomologist Andras Szito (DPIRD) believes is a species new to science. This was confirmed when samples were sent to a museum in Europe.

Agworld users have found vegetable weevils in canola near Wandering and weevils in canola at Gnowellen.

Brent Pritchard (Farmanco) found desiantha weevil at densities of 15 per square metre in a seedling canola paddock at South Stirlings . The paddock had received a spray application of bifenthrin at 200 mL/ha prior to seeding. Poor spray coverage is suspected to be the reason behind their survival rather than resistance.  The desiantha weevils were causing minor damage to the canola and will be monitored. Brent also reports finding desiantha weevils causing patches of minor damage in canola at Ongerup and Gairdner.

Three species of weevils typically damage canola: vegetable weevil, desiantha (spotted vegetable) weevil, and small lucerne weevil.

Identifying canola weevils

An adult vegetable weevil.
An adult vegetable weevil. Photo courtesy of: DPIRD

Vegetable weevils are about 10mm long with two short white stripes at an angle on each side of its abdomen. They prefer broadleaved plants, especially capeweed. They are often camouflaged amongst stubble and trash and tend to hide during the day.

Close up photo of a desiantha weevil.
An adult desiantha weevil. Photo courtesy of: Svetlana Micic (DPIRD)

Desiantha weevil adults are mottled grey-black in colour with grey flecks on the abdomen, and have the typical elongated weevil snout. They grow up to 7mm long and are flightless. Larvae are white, legless grubs with orange-brown heads, and grow to 8mm in length. Adults chew cotyledons, leaves and stems of canola plants, and may eat small plants down to ground level.

An adult small lucerne weevil
Adult small lucerne weevil. Photo courtesy of: DPIRD

Adult small lucerne weevils are about 5mm long, light grey in colour with a white stripe on each side.

Adult vegetable weevils often harbour in rock heaps and remnant bush areas, and move into the adjoining canola crop from these refuges. The other two weevils have been known to cause damage across the whole paddock.

Weevils can be very hard to find as they hide and play dead with their legs tucked, which helps them blend in with their surroundings.  Pitfall traps placed into the ground can be an effective way to find weevils.

If you are unsure of the type of weevil you have found in your canola crop use the PestFax Reporter app to request an identification by our entomologists.

Diagnosing weevil damage

Weevils chew off parts of leaves and cotyledons, giving them a serrated appearance and can eat plants down to ground level at high numbers.

Sometimes crop damage is restricted to paddock edges or where capeweed was in abundance the previous year.

Managing canola weevils

Weevils can be a frustrating pest as they can survive spray applications of insecticides at registered rates due to their behaviour of hiding during the day. For this reason, it can be more effective to spray in the evening when weevils are active.

For insecticide recommendations on managing vegetable weevils in canola, refer to DPIRD’s 2021 autumn winter insecticide spray guide. The vegetable weevil requires higher rates of insecticides than most pests of canola.

For more information on weevils visit DPIRD's Diagnosing weevils in canola page.

For more information contact research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591.



Article authors: Cindy Webster (DPIRD Narrogin) and Svetlana Micic (DPIRD Albany).

Rutherglen bugs are being found in pastures

  • Katanning
  • Mayanup

Rutherglen bug nymphs have been found by consultants in pastures east of Katanning and at Mayanup. Nymphs are estimated at 10 per 10cm square in patches, and there is a concern of potential damage in newly germinating renovated pastures.

Rutherglen bug
An adult Rutherglen bug. Photo courtesy of: DPIRD.

Rutherglen bug adults are 4mm long, have clear wings folded flat on the back, are grey-brown-black in colour and are very mobile.

Rutherglen bug nymphs
Rutherglen bug nymphs. Photo courtesy of: DPIRD.

Rutherglen nymphs have a pear-shaped, red-brown body. The nymphs do not resemble adults and can be confused for different species.

Swarms of the bugs, nymphs, and adults often move out from under plants when they are disturbed.

Damage from rutherglen bugs is similar to mite sucking in that seedlings will become stunted, discoloured, and distorted. Rutherglen bugs do most damage to moisture stressed plants.

Rutherglen bugs are often found in paddocks with weeds that germinated with summer/early autumn rains. Rutherglen bugs are especially partial to goosefoot, which is also commonly called mint weed.

Where weeds have been left uncontrolled close to seeding, surviving rutherglen bugs may pose a threat to emerging crops under dry and sunny conditions.

Rutherglen bugs prefer warm, dry conditions, and become inactive and die out with prolonged cold and wet winter weather patterns.

Most emerging crops will not have sufficiently high populations of rutherglen bugs to warrant spraying, but where they are in large numbers, chemical control of rutherglen bugs may be difficult. Repeat sprays are sometimes necessary against re-invading adults or late nymphal stages.

For insecticide recommendations, refer to DPIRD’s 2021 autumn winter insecticide guide.

For more information, see the department’s Diagnosing rutherglen bug and Rutherglen bug – economic considerations pages.

For more information, contact Svetlana Micic, Research Officer, Albany on +61 (0)8 9892 8591.



Article authors: Cindy Webster (DPIRD Narrogin) and Svetlana Micic (DPIRD Albany).

First field pea blackspot disease forecast for WA available online

Field pea with blackspot
Field pea with blackspot. Photo courtesy of: DPIRD.

The department’s first blackspot in field peas disease forecast for Western Australia for the 2021 season is now available online. It is current to 3 May 2021.

Blackspot becomes established when spores of the fungi produced on old field pea stubble are carried into the new crop by wind after rain events. Infection may occur at any stage of plant growth.

Rain that was received in many areas of the WA grain belt in late March, with follow up cyclonic showers during April, has meant that at many locations maturation of the blackspot fruiting bodies on previous season’s field pea stubble has started. 

For most locations, the blackspot risk is currently high and several more rain events will be needed before it is safe to sow field pea. In areas where sowing will be delayed, it would be worth considering additional weed management in paddocks that will be sown to field pea.

In a few areas around Esperance and at Mt Barker, the blackspot risk is already low.

DPIRD is urging growers in Scaddan, Grass Patch, and Salmon Gums to delay sowing until at least 10 May, and at Mt Barker it is not recommended to sow field pea until after 25 May. Sowing too early at these locations can result in a higher risk of frost damage later in the season.

To view the latest forecast, refer to DPIRD's Field pea blackspot management guide for Western Australia - 3rd May 2021.

For more information on blackspot, refer to the department’s Diagnosing blackspot in field peas webpage.

Blackspot Manager is a model that predicts the maturity and release of spores using weather data from the nearest weather station. Advice is given on when it is safe to sow field pea.

To subscribe to the free blackspot SMS service, text 'blackspot', your name, and nearest weather station to +61 (0)475 959 932 or email to subscribe to the direct email service.

For more information on blackspot in field peas, or the forecasts, contact Jean Galloway, Research Scientist, Northam on +61 (0)475 959 932.



Article author: Jean Galloway (DPIRD Northam) and Cindy Webster (DPIRD Narrogin).