Etiella in lentils

Etiella moth flights are likely to occur over the next four weeks. Lentil growers should plan to monitor because controls must target the adult stage

Etiella moth adult (left) and larvae on damaged pods (right) (Source: SARDI)

Where have they been reported?

SARDI entomologist Bill Kimber reports that Etiella moths have been detected during sweep netting in a lentil crop on the South Australian Yorke Peninsula. In Victoria and NSW, the period of peak emergence of Etiella moths, according to the Etiella degree-day model, is about two to four weeks away. Nonetheless, lentil growers should prepare for moth flights. Etiella, also known as the lucerne seed web moth (Etiella behrii), is a sporadic but serious pest of lentils in southern Australia.

About Etiella

Lentil crops are susceptible to Etiella damage as soon as the first pods appear, from late flowering stage onwards. Female moths lay eggs directly onto pods or their petiole. A key feature of the biology of Etiella is that the newly hatched larvae bore into immature pods within 24 hours of hatching to begin feeding on developing grain. Once inside lentil pods, larvae are protected from insecticide applications so sprays must target adult moths before egg lay commences.

For comprehensive information on Etiella that affect lentil crops, including their occurrence, lifecycle, behaviour and management strategies, go to Lucerne seed web moth or Etiella within the new PestNote series.

Predicted moth activity

The Etiella degree-day model predicts peak Etiella moth flight periods based on local temperatures - this can be used as a guide for when to commence monitoring. Daily minimum and maximum temperatures for a specific location need to be entered from June 21^st onwards. The date when the cumulative total of degree-days* (dd) first reaches 351 is the date to commence crop monitoring.

As of 21^st September 2015, cumulative degree-days based on actual temperatures and the approximate threshold date for Etiella flight activity based on 20 years of average temperature data at some lentil cropping areas were:

• Horsham (Vic) – 228 dd (about 17^th October)
• Swan Hill (Vic) – 274 dd (about 4^th October)
• Elmore (Vic) – 187 dd (about 24^th October) and
• Wagga Wagga (NSW) – 191 dd (about 18^th October).

The dates provided are only guides and will depend on temperatures over the next few weeks. Moth activity may occur either side of these dates.

To run the model yourself, download the Etiella degree-day model (XLS 64.5 KB). Temperature data for your local region can be obtained from the Bureau of Meteorology website. No further temperatures need to be recorded after a value of 351dd has been reached.

Our advice

Risk periods for Etiella within crops are when pods are green; dry pods are not at risk. Sweep netting is a common method used for estimating Etiella moth numbers in crops. Sample crops at least once a week during podding for evidence of Etiella activity. A minimum of 3 lots of 20 sweeps should be randomly undertaken within each crop. The recommended action threshold is 1-2 Etiella moths in 20 sweeps.

• Degree-days are a way of measuring insect development in response to daily temperatures.

 

Sources of field reports of Etiella

Bill Kimber – Entomologist, SARDI