Peak Etiella moth emergence not far off

Etiella moths are due to emerge in the near future. Remember, it’s the adult moth stage that must be targeted

Lentil crops are susceptible to Etiella (Etiella behrii) damage as soon as the first pods appear, from late flowering 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.

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

Forecasting moth activity

The SARDI Etiella degree-day model predicts peak Etiella moth emergence and 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 20^th September 2016, cumulative degree-days using 2016 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) – 200 dd (predicted October 19^th)

Swan Hill (Vic) – 260 dd (predicted October 4^th)

Bendigo (Vic) – 168 dd (predicted October 23^th)

Wagga Wagga (NSW) – 204 dd (predicted October 16^th)

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. Use the SARDI model to predict flight activity in your region. Once you reach this date, monitor lentil crops at least once a week 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.

Click here for comprehensive information on Etiella, including their life cycle, behavior and management.

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