PestFacts WA

Diamondback moth update

  • Eastern and Northern grainbelt
  • Bonnie Rock
  • Kalannie
  • Wailki
  • Beacon
  • Eradu
  • Walkaway
  • Mullewa
Two diamondback moth larvae captured by sweep netting canola
Two diamondback moth larvae captured by sweep netting canola. Photo courtesy of Amber Balfour-Cunningham (DPIRD).

Diamondback moth (DBM) caterpillar numbers have increased in canola crops in some eastern and northern grainbelt areas with some being above threshold and requiring insecticide application. Earliest germinated and/or stressed canola crops in the eastern and northern regions seem to be experiencing the highest DBM pressure at the moment.

Growers and agronomists are encouraged to inspect canola crops with an insect sweep net and be prepared to act to prevent economic damage.

Ty Henning (Ty’s Agri) reports that many canola crops at Bonnie Rock and Kalannie have above threshold numbers of DBM larvae, with more than 100 caterpillars per 10 sweeps.

Technical Officer Dave Nicholson (DPIRD) has found an average of 195 caterpillars (range 133 to 244) per 10 sweeps in an early podding crop at Wialki this week. This is up from two weeks ago where it was an average of 49 (range 30 to 62) per 10 sweeps. The crop was sprayed with 20 mL/ha of Trojan (gamma-cyhalothrin) three weeks ago, which DBM are fairly resistant to.

A grower at Beacon also had an increase in DBM larvae in an early podding crop from an average of 59 caterpillars (range 36 to 81) per 10 sweeps two weeks ago to an average of 70 (range 66 to 95) per 10 sweeps this week.

Peter Elliot-Lockhart (Elders) has been finding some canola crops in the Eradu and Walkaway areas with over 100 DBM caterpillars per 10 sweeps, but generally low numbers elsewhere (below 30 per 10 sweeps). Peter noted that he saw more DBM larvae in stressed crops, such as canola on sandier soil.

Another agronomist reported increased numbers of DBM larvae in the Mullewa and northern Geraldton regions.

However, canola focus crops being monitored by DPIRD, Mingenew Irwin Group, West Midlands Group and Liebe Group have consistently experienced low or no DBM larvae west and south of Kellerberrin. Ten focus crops being monitored by South East Agronomy Research in the Esperance region continue to find very low or no DBM larvae in sweeps but they have found increased numbers in some early sown (early germinated) canola crops, this was previously reported.

For information on DBM thresholds, insecticide resistance and strategic managementrefer to the GRDC GroundCover article Tactics to manage diamondback moth.

To read about previous DBM activity this season refer to the 2022 PestFacts WA Issue 9 article Diamondback moth.

For more DBM information refer to:

For more information contact:

  • Research scientist Svetlana Micic, Albany on +61 (0)8 9892 8591
  • Technical officer Alan Lord, South Perth on +61 (0)8 9368 3758.



Article authors: Dustin Severtson (DPIRD Northam).