PestFacts WA

Mind chemical withholding periods for native budworm sprays

Caterpillars

• Alma
• Nabawa
• Moonyoonooka
• Maya
• Dalwallinu
• Koorda
• Mukinbudin
• Wyalkatchem
• Northam
• York
• Kendenup

A native budworm caterpillar. Photo courtesy of: DPIRD.

Jack Watson (Elders) reports finding above threshold numbers of budworm caterpillars in pulse and canola crops at Mukinbudin, Wyalkatchem, Koorda and Northam.

Department of Primary Industries and Regional Development (DPIRD) staff have also reported above threshold numbers of native budworm caterpillars in canola crops at Moonyoonooka (84 caterpillars per 10 sweeps), Nabawa (60 per 10 sweeps) and Alma (42 per 10 sweeps).

These high caterpillar numbers are not unexpected given the very high numbers of budworm moths that have been recorded flying into the grain growing areas over the last month.

DPIRD staff found less than 1 budworm caterpillar per 10 sweeps in canola at Northam, York and Kendenup. However, because high numbers of budworm moths have been recorded flying into some of these areas (see Native budworm moth section below) in recent weeks, it is likely that caterpillar numbers could increase in the coming weeks.

A farmer near Maya sweep netted a couple of lupin crops and found less than one budworm caterpillar per 10 sweeps. The caterpillars captured were up to 10 mm in length.

An agronomist has reported finding 2 budworm caterpillars per 10 sweeps in a lupin crop west of Dalwallinu.

The cold, wet and windy weather that arrived late this week may help reduce the numbers of eggs and small caterpillars to some extent. Eggs may be dislodged, and small caterpillars may become stuck or drown. Predators, parasites and disease can also affect population numbers. However, given the number of native budworm caterpillars already found at some locations, and the very high numbers of moths that have been recorded migrating into some areas in recent weeks, regular sweep net monitoring of susceptible crops will be required to determine if control measures are needed.

Native budworm moths

• Usual trapping locations

Native budworm moth flights have moderated in some areas while other locations have once again reported very high numbers of moths being captured.

Native budworm moths captured in a pheromone trap at Moonyoonooka on 20 September 2024. Photo courtesy of: Surya Dhakal (DPIRD).

The highest native budworm moth captures for each location from the last 2 weeks include: Moonyoonooka (1438 moths over 3 weeks), Maya (1193), York (1119), Dalwallinu (980), Bindi Bindi (850), South Stirlings (800), Borden (572), Kellerberrin South (545), Varley (448), Kellerberrin North (404,) Nabawa (398 over 3 weeks), Northam (363), Cadoux (261), Dowerin (194) and Cunderdin (175). There have been lower moth captures recorded at Narrogin (82), Kendenup (79), Cuballing (65), Boyup Brook (53) and Kojonup (41).

A map showing the native budworm moth flights recorded so far this season is available at Cesar Australia’s MothTrapVisWA page.

Management

Growers who are contemplating spraying maturing canola, lupins and field peas in the coming weeks should be mindful of chemical withholding periods (WHP) and check chemical labels before spraying. The minimum times required between the spray application date and harvesting or windrowing crops can vary from 0 to 28 days (see Table 1 below) depending on product.

Growers and agronomists can access DPIRD’s free MyPestGuide CropScout application and enter their results into the sweep net module to calculate native budworm spray thresholds quickly in the field.

Pesticide options for the control of native budworm can be found in DPIRD’s 2024 Winter Spring Insecticide Guide.  

Further information  

Detailed information on this pest can be found at the department’s Management and economic thresholds for native budworm. 

To read about prior native budworm activity this season refer to the 2024 PestFacts WA newsletter articles in:

• Issue 17 Check your crops for native budworm caterpillars
• Issue 16 Native budworm moth activity update
• Issue 11 Native budworm caterpillars are active
• Issue 5 Native budworm moth flights have started. 

For more information contact Alan Lord, Technical Officer in Perth on +61 409 689 468.

Article author: Alan Lord (DPIRD Perth).