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Native budworm

* Pheromone trap catches in the last two weeks have declined. * Sweep net monitoring of budworm suggest low to modest infestations. * Grub damage will reach a peak late October, but may remain below threshold.

 

Where have they been reported?

Pheromone trap catches for native budworm (Helicoverpa puntigera) in the past two weeks have generally declined relative to those observed in early-mid September (see Update - Budworm catches & forecasts 8th Oct 14). The highest catches were recorded at Bordertown, SA and at Mittyak in Victoria’s northern Mallee. Nonetheless, even these catches are relatively small in comparison to those that typically precede major outbreaks of native budworm. In other areas of the Victorian Wimmera and Mallee, moth catches have been relatively low. In addition, there have been no more moths caught in traps further north in South Australia where many of the early season moths presumably arose. The particularly dry conditions in South Australia, Victoria and Southern NSW since July appear to have taken their toll on budworm populations.

Reports of crop monitoring for native budworm reveal a range of infestation levels. In the Victorian Wimmera, average budworm measures were 0.5 to 1 per 10 sweeps in faba beans at Rupanyup; nil in faba beans at Warracknabeal; and very few in other crops samples in the western Wimmera. In the Victorian Mallee, there were 0.5 per 10 sweeps in faba beans (early podding) at Kerang, and 2 per 10 sweeps in faba beans at Berriwillock (now sprayed).

In the NSW Central West Slopes & Plains, low numbers have been recorded in beans and lupins, substantially lower than in previous years. Similarly, populations in the NSW Riverina near Ariah Park are not causing great concern.

Predictive modelling

Moths arriving in flowering crops will generally (but not always) start egg-laying immediately. Our predictive tool (Darabug) uses average daily temperatures for 3 different locations/stations from which to generate forecasts of budworm development rates. Budworm growth rate predictions from the largest flight on the 7th September suggest third instar budworm will peak in crops next week (2nd week of October) in the Mallee and NSW Riverina. Predictions from the latest moth catches, assuming egg-laying commenced around the 26th September and continued through until 3rd October, indicate that third instar caterpillars are likely to appear in susceptible crops in the last week of October in the Mallee and southern NSW; a little later in the Wimmera, assuming crops persist.

Second and third instar budworm are reasonably easily seen in sweep nets, and relatively easily controlled, particularly with biologically active insecticides. Fifth and sixth instar are the budworm stages that tend to inflict most serious crop damage.

These predictions are only guides; development rates will vary if temperatures are above or below average.

Our Advice

Spraying for native budworm in many areas is unlikely to be warranted at present. Monitor crops regularly using sweep nets; it is important to sample representative parts of the entire paddock prior to making a control decision. Taking multiples of 10 sweeps in at least five locations in a paddock is recommended. Economic thresholds for native budworm should be followed. These vary according to crop, control costs and anticipated crop return. Generally lentils, field peas and faba beans have much lower thresholds than lupins and chickpeas. These thresholds are based on yield loss, not seed quality. Please note that sudden hot days can drive young caterpillars directly in to pods.

See PestFacts Issue No. 10 further information about native budworm identification and management.

 

* Sources of field reports of native budworm

Ben Cordes – Agronomist, Tylers Hardware & Rural Supplies (Victorian Wimmera)

Terry Edis - Agronomist, Landmark (NSW Central West Slopes & Plains)

Adam Pearce – Agronomist, Clovercrest Consulting (Victorian Wimmera)

David Strahorn – Agronomist, Delta Ag (NSW Riverina)

We thank the following for running traps to support this forecast service:

South Australia:

   Peter Gregg and Alice del Socorro - University of New England (Armidale) and Bill Kimber – SARDI (Adelaide)

Victorian Wimmera:

   Bill Gardner (Agronomist), Ben Cordes (Tylers Hardware & Rural Supplies) and Robert Smith and Co at Warracknabeal

Victorian Mallee:

   Rob Sonogan (AGRIvision Consultants), AGRIvision Consultants at Beulah & Ouyen, Landmark at Berriwillock, Agronomic Results at Kerang, CropRite at Swan Hill and Michael Clarke at Berriwillock

NSW Riverina:

   David White (Delta Agribusiness)

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