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Etiella

* The temperature threshold for Etiella moth flight is likely to be met over the next 3 weeks. * Control strategies need to be focussed at the moth.

 

Where have they been reported?

Concern is growing about the imminent emergence of Etiella (Etiella behrii) moths, particularly in the Swan Hill area of the Victorian Mallee. Lentil growers should start preparing for moth flights. Etiella, also known as the lucerne seed web moth, is a sporadic but serious pest of lentils in southern Australia, and can cause yield losses and damage grain if not controlled.

Etiella habits and behaviour

A key feature of the biology of Etiella is that young larvae bore into immature pods within 24 hours of hatching to begin feeding on developing grain. Once inside the pods, larvae are protected from insecticide applications so sprays must target adult moths before egg lay commences. Etiella also attack lucerne and occasionally clover, peas and lupins.

The Etiella degree-day model predicts the peak Etiella moth flight period based on local temperatures and 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 21st onwards. The date when the cumulative total of degree-days (dd) first reaches 351 is the date to commence crop monitoring. No further temperatures need to be recorded after a value of 351dd has been reached.

As of 23rd September, the cumulative degree-days (and the approximate threshold date for flight activity) at some locations were: Horsham (Vic) – 220 dd (about 13th October); Swan Hill – 336 dd (about 27th September); Bendigo (Vic) – 216 dd (about 12th October); and Wagga Wagga (NSW) – 247 dd (about 9th October). The dates provided are only guides and will depend on temperatures over the next three weeks.

Monitoring and control options

Sweep netting is a common method used for estimating Etiella moth numbers in crops. Lentil crops should be sampled at least once a week during podding for evidence of Etiella activity. A minimum of 3 groups of 20 sweeps should be randomly undertaken within each crop. Recommended action thresholds are 1-2 Etiella moths in 20 sweeps. Pheromone traps and light traps are also useful monitoring techniques.

Description

Etiella moths are 10-15 mm long, slender, grey-brown in colour and have a prominent beak. The forewings have a distinct white stripe running the full length along the front edge. Larvae are cream-pale green in colour with several pink-red stripes running along the back. They have a red-brown coloured head and grow up to 15 mm long. Female moths lay their eggs under the calyx or on the pod surface, and these hatch in 4-7 days depending on temperature.

 

* Sources of field reports of Etiella

Nick MacNamara – Agronomist, Dogshun Medlin consultants (Victorian Wimmera)

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