Monitoring of native budworm: moths and caterpillars

Native budworm moths have now been caught in most major cropping districts of Victoria and southern New South Wales. The first sightings of caterpillars have also been reported.

Native budworm (Helicoverpa punctigera) breeds during winter on flowering plants in inland Australia when there is sufficient rainfall for broadleaf vegetation to flourish (they have a very wide host range!).

When this inland vegetation dies off in late winter/spring, the caterpillars pupate, and moths emerge in readiness to migrate to agricultural regions.

Every year, with the help of advisers and growers, we monitor for an influx of moths in key cropping regions with pheromone traps from early August.

The presence of moths in traps signals egg laying in crops including several pulses and oilseeds.

When eggs hatch, ensuing caterpillar populations will feed on pods and flowers.

Native budworm moths have now been caught in most major cropping districts of Victoria and southern New South Wales.

The first sightings of native budworm caterpillars have also been reported from lentil and field pea crops in northern regions of the Victorian Mallee. The caterpillars observed in these crops range from 2 to 15 mm long.

Will the weather affect native budworm larvae?

Native budworm may be at an advantage in regions where there are drier than usual conditions. 

Helicoverpa moth species lay their eggs singly or in groups of twos or threes near the growing points of plants, but not all eggs will make it to the damaging caterpillar stage. There are a number of factors that can impact egg survival, including rain.

A study by Kyi et al. (1991) demonstrated clear effects of rain on egg mortality of the closely related Helicoverpa armigera in cotton. 

In this field trial study, the effect of simulated and actual rain was assessed. Rainfall was deemed an important factor in causing egg loss due to dislodgment from the plants.

In any case, continued monitoring is essential as we move into the warmer months.

Native budworm larvae monitoring

Sweep netting is a quick and easy method to sample most short crops such as lentils and field peas during spring.

Sweep netting is weather dependent and cannot be used when the vegetation is wet.

This type of trapping targets the canopy of the crop – insects found lower on the plant may be missed. 

Sweep netting instructions:

  1. Hold the net handle with both hands. The net should be at a slight angle (the bottom of the net being forward). Each sweep should consist of moving the net through the crop in an arc of approximately 180°.
  2. Sweep the crop canopy, making sure the edge of the net brushes the vegetation. The sweeping motion should be steady, but not excessively fast. The final sweep should be followed by a quick swing and the net closed rapidly by flipping the frame over.
  3. Insects can be observed and counted directly in the net. Alternatively, the contents of the net can be emptied into a tray, however be aware that some insects will fly away rapidly.

This technique may be less efficient in tall dense crops of faba beans, lupins and chickpeas, although still useful to give relative counts. 

Monitor crops for activity by taking a minimum of 5 sets of 10 sweeps and calculating the average number of caterpillars per 10 sweeps.

A sweep netting demonstration.

A beat sheet can be used to monitor in taller or more rigid crops, especially wide row chickpeas and faba beans.

A standard beat sheet (plastic or canvass) is about 1.3 metres wide and 1.5 metres long, with a heavy dowel to weigh it down. One edge should be placed at the base of a row and the sheet spread out across the inter row space. If rows are narrow then it can be draped over the adjacent row.

Using a 1 metre long rod, vigorously shake the row 10 times over the sheet to dislodge and catch caterpillars.

How to use a beat sheet – demonstrations in chickpea.

For further information on native budworm, including economic thresholds, visit our comprehensive PestNote.


Field observations

Brad Bennett, AGRIvision (Mallee VIC)

Shayn Healey, Crop Rite (Mallee VIC)

Andrew McMahen, Landmark (Mallee VIC)

Matt Witney, Dodgshun Medlin (Mallee VIC)

Many thanks to the coordinators and counters participating in our moth trap program, including:  

Brad Bennett, AGRIvision (Mallee VIC)

Neilson Carr (Central VIC)

Jim Cronin, Landmark (Central West Slopes & Plains NSW)

Adam Dellwo, Elders (Riverina NSW)

David Bufton (South West VIC)

Rob Fox, AGRIvision (Wimmera VIC)

Bill Gardner (Wimmera VIC)

Sarah Groat, Ag Grow Agronomy and Research (Riverina NSW)

Barry Haskins, Ag Grow Agronomy and Research (Riverina NSW)

Shayn Healey, Crop-Rite (Mallee VIC)

George Hepburn, Tylers Hardware and Rural Supplies (Wimmera VIC)

Damian Jones, Irrigated Cropping Council (Mallee VIC)

Annieka Paridaen, Premier Ag Consultancy Group (South West VIC)

Andrew Rice, ASPIRE agri (Central West Slopes & Plains NSW)

Max Ridley, Landmark (Central West Slopes & Plains NSW)

David White, Delta Agribusiness (Riverina NSW)

Rachel Whitworth, Ag Grow Agronomy and Research (Riverina NSW)

Cover image: Photo by Matt Witney

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PestFacts south-eastern keeps growers and advisers informed about invertebrate pests and beneficials in broadacre crops and pastures during the winter-cropping season in Victoria and southern New South Wales.


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