Native budworm

* Pheromone trap catches in the first 20 days of September have been modest in comparison to previous years. * Catches in the Victorian Mallee and southern Wimmera have been highest. * Most damaging infestations may not occur until late October.

 

Where have they been reported?

Low infestations of native budworm eggs (white to cream) on young pods and caterpillars have been detected in lupins around Gilgandra in the NSW Central West Slopes & Plains. The crops are being regularly monitored. Low levels of beneficials were also observed. Similarly, in the Victorian Mallee, native budworm caterpillars have been found in lupins at the rate of 2-3 caterpillars per 10 sweeps.

Native budworm habits and behaviour

Native budworm (Helicoverpa punctigera) larvae are a major pest of all pulses and canola during spring to early summer. They feed on buds, flowers, fruiting parts and seeds, and also attack pasture seed crops of lucerne, annual medic and clover. Infestations occur following migratory flights of adult moths into southern agricultural regions, usually from inland pastoral regions of SA and NSW. When moths arrive and lay eggs in crops the resulting caterpillars can cause serious damage if left uncontrolled. For more information on native budworm, click here.

Early warning through moth traps

A native budworm moth-trapping network of pheromone traps has now been established as a trial across south-eastern Australia. This is through a collaboration between cesar, the University of New England, SARDI and AGRIvision Consultants. Pheromone traps specifically attract male moths of native budworm and provide a good indication of current female egg-laying activity (see PestFacts issue No. 9 for full details).

In comparison to some previous year’s trap records, moth catches in most Victorian and NSW trap sites in the first 20 days of September have been modest. Some regions have had notably higher moth tallies: catches in South Australia and the Victorian Mallee and northern Wimmera were higher than elsewhere up until the 12 September and have declined sharply over the past week, except at Mittyak in the Mallee (180 moths). Traps in the southern Wimmera and NSW Riverina have recorded consistently low catches, suggesting minimal egg-laying in these areas.

The moth catches are likely to have arisen from the north-westerly winds on the 7th September. In contrast, the low-pressure system currently moving across the south-eastern cropping area, bringing limited rain to some areas, will have been preceded by a north easterly air stream that may introduce new moths from western and central NSW. Large moth migrations are not expected during this time. Further north-westerly winds (and moth flights) are expected on the 28th and 29th September.

Caterpillar growth rates

Our predictive tool (Darabug) uses a limited range of meteorological stations from which to generate forecasts of budworm development rates. Assuming egg-laying commenced on the arrival on the immigrant moths on 7th September and continued through until 19th September, the following table lists the approximate dates for budworm egg hatch and 3rd and 5th instar development, using average daily temperatures for 3 different locations.

Assuming egg lay 7th-19th Sept

	Horsham, Vic	Swan Hill, Vic	Griffith, NSW
Egg hatch (= 1st instar)	25 Sep - 4 Oct	20 Sep - 1 Oct	21 Sep - 2 Oct
3rd instar (mid stage)	22 - 28 Oct	12 - 22 Oct	13 - 22 Oct
5th instar	3 - 9 Nov	24 - 30 Oct	25 - 31 Oct

These are only guides; development rates will vary if temperatures are above or below average. For complete details of catches, forecasts and a caterpillar size guide, see Update - Budworm catches & forecasts 24th Sep 14.

Monitoring and control options

To sample for budworm, multiples of 10 sweeps should be taken in several parts of the crop, and caterpillars carefully distinguished from other larvae, including beneficial hover flies.

2nd and 3rd instars are reasonably easily seen in sweep nets or a beat sheet, and relatively easily controlled with insecticides, particularly with biologically active products such as Gemstar® and Vivus Gold®. 5th and 6th instars tend to inflict most serious crop damage.

Lupins and canola have much higher thresholds than other pulses. Entomologists from DAFWA have calculated the following dynamic economic threshold for native budworm for use in various crops: ET = (C x 1000) / (K x P). Further information can be found here.

Our advice

Monitoring for native budworm larvae should commence in pulse and canola crops entering the susceptible flowering and podding stages. Be warned that in response to abruptly hot conditions, young larvae will burrow directly into pods, whereas they more often surface graze on pods when the temperatures are less extreme. Early mortality of eggs and young caterpillars can be exceptionally high following disturbed wet or moist and windy conditions. Use thresholds to guide spray decisions.

Description

Native budworm larvae can be up to 40 mm long with substantial colour variation (shades of brown, green and orange), usually with darkish strips along the body and bumpy skin with sparse stiff black hairs. Newly hatched larvae are light in colour with dark brown heads and spots, and as they develop they become darker in colour. Adult moths are approximately 30-35 mm long, light brown to red-brown, with numerous dark spots and blotches.

 

* Sources of field reports of native budworms

Glen Shepherd – Agronomist, IMAG Consulting (NSW Central West Slopes)

Andrew McMahen – Agronomist, Landmark (Victorian Mallee)

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)