Diamondback moth and other caterpillars found in crops
Diamondback moth
- Tenindewa
- Northam
- Southern agricultural region
Diamondback moth (DBM) caterpillar numbers have further increased in some canola crops in the northern and central agricultural region over the past fortnight, while remaining low in many canola crops in the southern agricultural region.
Caterpillar numbers can vary significantly from week to week within crops. Growers and agronomists are encouraged to inspect canola crops using an insect sweep net and to be prepared to act if numbers have reached thresholds that could lead to economic damage. The DBM control thresholds are 100 or more caterpillars per 10 sweeps at late flowering (without moisture stress), and 150 to 200 caterpillars per 10 sweeps at pod maturation.
Surya Dhakal, DPIRD Technical Officer has found a range of 0 to 480 DBM caterpillars per 10 sweeps (with an average of 238 per 10 sweeps) in podding canola at Tenindewa. This is double the number recorded 14 days earlier.
Danae Warden, DPIRD Technical Officer has found 300 DBM caterpillars per 10 sweeps in a canola research trial near Northam. The crop had been sprayed with alphacypermethrin and chlorpyrifos early in the season. The crop will now be sprayed with cyantraniliprole.
In the southern agricultural region below threshold DBM numbers have been reported in the past week. Joel Kidd, DPIRD Technical Officer has found below threshold DBM larvae numbers at Cascade, Neridup, Howick, Munglinup, Gibson and Dalyup. Daniel Malecki-Lee, DPIRD Technical Officer also found below threshold DBM larvae at Gnowellin, South Stirlings, Kendenup and Amelup.
Monitoring and managing diamondback moths
Growers and agronomists can access DPIRD's free MyPestGuide CropScout application and enter their results into the sweep net module to calculate insect spray thresholds quickly in the field.
Growers and agronomists are reminded that DPIRD research trials have shown that late season application of insecticide, especially multiple sprays, against DBM is less likely to result in a profitable outcome compared to early and mid-season pest control. For information on DBM monitoring and management, refer to the 2024 PestFacts WA Issue 14 article Diamondback moth activity is increasing in some crops.
For more information on DBM activity in the past month refer to the 2024 PestFacts WA Issue 15 article Increase in diamondback moth numbers.
Other caterpillars
- Watercarrin
- Kauring
- Northam
Some areas of the WA grainbelt are experiencing warmer and drier than average spring conditions, along with increased caterpillar pest activity in crops.
Amber Balfour-Cunningham, UWA Research Scientist recently found several less commonly seen caterpillar pests causing low level damage in a canola crop at Watercarrin, north of Cunderdin.
A tobacco looper, Chrysodeixis sp., caused chewing damage to podding canola and Amber found 5 to 10 pods showing 50% damage on 3 to 4 stems of the plant.
In the same canola crop at Watercarrin, Amber found white-winged wedge-moth caterpillars (Capusa cuculloides) chewing on canola stems and pods in various locations within the crop. Deb Donovan, DPIRD Technical Officer also found the same caterpillar species causing chewing damage in a crop near Kauring, east of York.
Cabbage white butterfly (Pieris rapae) caterpillars have also been reported chewing canola pods at Northam by Amber Balfour-Cunningham.
Further Information
If you are finding any unusual caterpillars causing damage in your crop you can use the PestFacts WA Reporter app to report your findings and request an identification.
For more information contact Dustin Severtson, Research Scientist in Northam on +61 8 9690 2160, Alan Lord, Technical Officer in South Perth on +61 8 9368 3758 or Svetlana Micic, Research Scientist in Albany on +61 8 9892 8591.
Article author: Bec Severtson (DPIRD Northam).