PestFacts WA

Be mindful of chemical withholding periods if spraying for native budworm

Caterpillar activity and management

• Eurardy
• Yuna
• Northampton
• Maya
• Pithara
• Kirwan
• Bencubbin
• Trayning
• Cascade

A native budworm caterpillar feeding on a canola pod. Photo courtesy of: DPIRD.

Technical officer Dave Nicholson (DPIRD) reports finding 10 native budworm caterpillars per 10 sweeps in a lupin crop near Yuna. Dave also sweep netted some other lupin crops in the area and found one caterpillar per 10 sweeps at Northampton and less than one per 10 sweeps near Eurardy.

A budworm trapper near Maya reports finding less than one native budworm caterpillar per 10 sweeps in a lupin crop.

An agronomist has found nine caterpillars per 10 sweeps in podding canola crop near Pithara.

Ty Henning (TekAg) reports that susceptible crops in the Kirwan area are being sprayed for above threshold numbers of native budworm caterpillars. Ty reported finding between six and 13 budworm caterpillars per 10 sweeps in a lupin crop near Kirwan.

A farmer near Bencubbin recently sweep netted six canola paddocks across their property and all paddocks had above threshold numbers of budworm (eight to 12 budworm caterpillars per 10 sweeps). Caterpillars were less than 10mm in size. The canola crops will be sprayed in the next few days.

Technical officer Amber Balfour-Cunningham (DPIRD) has found low levels (less than one per 10 sweeps) of budworm caterpillars in late flowering canola crops near Bencubbin and Trayning.

An agronomist reports finding around four budworm caterpillars per 10 sweeps in a canola crop near Cascade.

The economic spray threshold levels will vary with crop type, grain price and control cost. These thresholds can be calculated for each grower's particular situation using a simple formula outlined at the department’s native budworm threshold table.

Growers who may be contemplating spraying maturing canola, lupins and field peas should be mindful of chemical withholding periods (WHP) and to check chemical labels before spraying. Minimum times required between the spray application date and harvest or windrowing crops can vary from 0-28 days (see Table 1 below).

Native budworm moth trapping surveillance

• Usual automated and manual trapping locations

An adult native budworm moth. Photo courtesy of: DPIRD.

Native budworm flights continue to move westwards with low numbers of moths now being caught southwest of Kojonup over the past few weeks, and the first captures of moths reported near Spencers Brook. There has also been a large increase in moth numbers captured across a number of locations during the last week.

The higher moth captures this week include: Dowerin (291 moths), Cunderdin (280), Wyalkatchem (242), Dalwallinu (222), Southern Cross (159), Walebing (150), Kirwan (145), Varley (94), Maya (86), Merredin (60), Cuballing (48), Spencers Brook (46), Narrogin (43) and Doodlakine (40).

Results of this week's manual trappings are available at the department’s Native budworm moth numbers 2021.

A mapped view of the native budworm trap captures is available at Cesar Australia’s MothTrapVisWA page. Viewers need to select the desired trapping date range.

In summary native budworm moth migrations in the 2021 season have concentrated in the north and east of the WA grainbelt from June to September. Similar to 2020, moths first started appearing in June, north of Geraldton before migrating along the eastern grainbelt (see map below). These numbers have been recorded by the manual and automated native budworm moth surveillance co-funded funded by DPIRD, GRDC and Hort Innovation’s iMapPESTS project.

Native budworm moths caught in WA from June to late September 2021. Note change of scale between each month. Map shows estimated numbers of the total monthly moth trap count. Maps courtesy of: Christiaan Valentine (DPIRD).

Pesticide options for the control of native budworm can be found in DPIRD’s 2021 winter spring insecticide guide.

Detailed information on this pest can be found at the department’s Management and economic thresholds for native budworm or listened to on the recently published Native budworm podcast.

For more information contact Technical Officer Alan Lord, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.

Article author: Alan Lord (DPIRD South Perth).

Article input: Christiaan Valentine (DPIRD Northam).