A new program of trapping for native budworm

A new collaborative program of trapping of native budworm moths across south-eastern Australia will help focus efforts in monitoring for caterpillars in pulse and canola crops

 

Trapping network

cesar is collaborating with colleagues from the University of New England, SARDI and agronomists / growers in the Victorian Wimmera and Mallee and NSW Riverina to provide an advanced warning system for native budworm (Helicoverpa punctigera) infestations in the southern cropping zone.

It is well known that native budworm moths are capable of migrating hundreds, if not thousands, of kilometres in late winter and spring. Typically, moths migrate from the north west, often originating from inland regions that have previously benefited from intense, episodic rainfall events in autumn and winter (as in 2014, see PestFacts Issue No. 8).

A broad network of pheromone (female sex scent) traps has now been established covering cropping and non-cropping areas of the North West Pastoral and Eastern Eyre Peninsula districts of South Australia, the Victorian Wimmera and Mallee and NSW Riverina. Pheromone traps specifically attract male moths of native budworm and often provide a good indication of current female egg-laying activity.

Forecasts

From weekly (and projected 10-day) moth catches and climate records, we can estimate:

• possible movement of moths, mostly into districts to the south or southeast;

• likely egg hatch dates (first instar) for different regions, assuming that moths lay eggs locally and that their eggs survive environmental conditions (rainfall, temperature extremes, local parasitism);

• dates on which the young caterpillars may first become detectable in sweep nets (2nd or 3rd instar);

• the approximate catch thresholds at which crop monitoring should commence.

The forecast dates are based on a growth-rate model for native budworm larvae, which uses average regional temperatures. For example, eggs laid in the Victorian Mallee would take about 16 days to hatch from the 1st September, but only 10 days if laid on 1st October.

This approach has been successfully used for native budworm in southern Australia in the past, and continues to be used in Western Australia. However, it is only a guide. Previous research has demonstrated that egg-laying peaks can be directly related to moth catch peaks, but peaks in egg-laying can sometimes occur in the absence of peak moth catches. The traps are also sparsely distributed which reduces the resolution of predictions.

Current moth activity

For the past week, trap catches have been low in most areas except for Minnipa in the Eastern Eyre Peninsula of SA. It is unlikely that moth flights from this region would impact on Victorian or NSW cropping zones. Nonetheless, there has been some moth activity casually observed in the Victorian Wimmera in August, which will have resulted in small numbers of larvae in some flowering crops. As canola in most districts has commenced flowering, indicative damage thresholds for canola are 5-10 larvae per 10 sweeps.

 

* Acknowledgements

We thank the following for providing information to support this forecast service

South Australia

    Peter Gregg and Alice del Socorro - University of New England (Armidale)

    Bill Kimber – SARDI (Adelaide)

Victorian Wimmera

    Ben Cordes (Agronomist, Tylers Hardware & Rural Supplies)

    Bill Gardner (Agronomist)

Victorian Mallee: Rob Sonogan (Agronomist - AgriVision Consultants)

NSW Riverina: David White (Agronomist - Delta Agribusiness)