Native budworm moth numbers are high
Caterpillar activity reports
A grower near Mullewa sprayed his pre-flowering lupin crops with alphacypermethrin last week after finding concerning levels of budworm caterpillars up to 30 mm long. This indicates that moths had migrated into the crops and laid eggs early to mid-July.
Grant Thompson (Crop Circle Consulting/Landmark) reports that budworm caterpillars are being found in early budding lupins, budding canola and vegetative cereals at Yuna and Mullewa. Economic thresholds will be applied for spraying.
Binnu farmer Peter Cripps has applied a control spray of alphacypermethrin to his lupin crop after finding increasing numbers of budworm caterpillars in recent weeks.
Technical officer Joanne Walker (DPIRD) reports finding 1 budworm caterpillar (5mm) per 10 sweeps in a lupin crop near Geraldton and 5 caterpillars (5mm) per 10 sweeps in a lupin crop near Walkaway.
Peter Norris (Synergy Consulting) has reported finding what appears to be native budworm caterpillars feeding on an early tillering wheat crop west of Eradu and another wheat crop at ear emergence north of Mullewa.
While native budworm have occasionally have been recorded feeding on cereals, they could be the closely related species the lesser budworm. Lesser budworm have a wide host range and will feed on both broad leaf crops and cereals. Whereas native budworm prefer broad leaf and legume crops, and are rarely found on cereal crops.
Peter also reports finding 2 budworm caterpillars (10mm) per 10 sweeps in a lupin crop north of Mullewa.
Richard Quinlan (Planfarm) has also found what appears to native budworm caterpillars causing damage to a wheat crop near Eradu.
Native budworm moth trapping surveillance
Some large native budworm moth captures have been reported this week, particularly in the northern eastern grainbelt areas. The higher captures this week include Bindi Bindi (371 moths), Maya (208), Dowerin (155), Kiwan E (155), Binnu (154), Walkaway (141), Dalwallinu (128) and Badgingarra (78).
The budworm moth trapper near Binnu has caught 1,288 moths over the last 4 weeks, and commented that it is the highest numbers of moths he has ever seen at this time of year. A look back over the records from recent years would indicate that he is correct.
The very high Binnu moth trap numbers are supported by an indirect report from a pastoral property in the Murchison region of unusually high numbers of budworm moths in the area this year. This would suggest that much higher numbers of budworm moths than normal are likely to find their way into parts of the cropping zone this year.
Results of this week's automated and manual trappings are available at the department’s Native budworm moth numbers 2019.
A mapped view of the native budworm trap captures is available at cesar’s MothTrapVisWA page. Viewers need to select the desired trapping date range.
Why are there unusually high numbers of budworm moths?
Every year native budworm moths migrate seasonally on prevailing winds, from around July, from pastoral areas north and east of the WA grainbelt in a southern and westward direction. The timing of migration and number of moths varies from year to year, and surveillance of the moths aids in being able to target monitoring for caterpillars and deciding upon insecticide sprays and timing.
While it is not unusual to have high budworm numbers in some isolated locations at this time of year, the numbers being reported this year are unusually high over a wide area. It is possible that the large moth flights are a result of 1) summer/autumn rain in the pastoral areas which provide food for build-up of budworm prior to migration and 2) high pressure cells causing north-easterly winds encouraging long distance movements.
Pulse and canola growers in north and central areas are encouraged to monitor their crops using a sweep net or bashing plants into a container if they are too short to sweep. Serradella, lucerne, clover and annual medic seed crops should also be regularly checked for native budworm caterpillars.
With high moth numbers being detected by DPIRD’s moth trapping network in recent weeks in northern and central regions, growers are at increased risk of caterpillars being present. However, high moth numbers do not always equate to high caterpillar numbers due to fungal infection, predators and other natural processes, so it is important to monitor for caterpillars to see if spraying is necessary.
Distinguishing native budworm caterpillars from lesser budworm caterpillars
The lesser budworm (Heliothis punctifera) is closely related, and looks similar to, the native budworm (Helicoverpa punctigera).
Lesser budworm larvae are usually dark in colour, while native budworm varies from black to green to light brown in colour. Both have a light coloured strip down each side of the body. For older larvae (>20mm in length), lesser budworm has white hairs on the collar (segment behind the head) and the body, while native budworm has black hairs on the collar and black to blackish-brown body hairs.
Lesser budworm moths are generally darker in colour than the native budworm, which are light brown to reddish-brown. Adult moths also have a distinctive pattern on the forewing, whereas the native budworm typically have wings that are lighter in colour and have less obvious patterns (although this is variable).
The lesser budworm is an infrequent pest while native budworm occurs in most years.
If you have found caterpillars that appear to be native budworm feeding on cereals, and would like confirmation of the species please send samples to:
Department of Primary Industries and Regional Development
75 York Road, Northam WA 6401, attention to Dusty Severtson.
For more information on managing and distinguishing budworm caterpillars refer to GRDC’s recently updated Insects of Southern Australian Broadacre Farming Systems Identification Manual and Education Resource 2nd Edition. Particularly Section 4: Common Pest, Beneficial and Exotic Species.
Detailed information on this pest can be found at DPIRD’s Management and economic thresholds for native budworm page and 2019 PestFax Issue 12 article Native budworm moth trapping and caterpillar activity.
Pesticide options for the control of native budworm can be found in the department’s Winter/Spring Insecticide Spray Chart 2019.
For more information contact:
Alan Lord, Technical Officer, South Perth
+61 (0)8 9368 3758 or +61 (0)409 689 468
Article author: Alan Lord (DPIRD South Perth).