Look out for Etiella

Etiella (Etiella behrii), also known as the lucerne seed web moth, is a sporadic but serious pest of lentils in southern Australia. They also attack lucerne, field peas and pasture legume crops. Successful control is dependent on careful crop monitoring, as insecticide sprays must target adult moths before egg lay commences. Failure to identify Etiella moths early can lead to significant yield losses at harvest.

Etiella moths are slender, 10-15 mm long, grey-brown in colour and have a prominent beak. Their wingspan varies between 20-25 mm and the wings are held over the body when at rest. 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, have a red-brown coloured head and grow up to 15 mm long.  

Etiella eggs are about 0.5 mm in diameter and become a pink-orange colour prior to hatching. Female moths lay their eggs under the calyx or on the pod surface, and these hatch in 4-7 days depending on temperature. Newly hatched larvae bore into immature pods within 24 hours to begin feeding on developing grain. This results in inferior quality lentils and yield losses due to a reduction in grain weight and grain breakage. Once inside the pods, larvae are protected from insecticide sprays and damage is usually only identified at harvest.

A degree-day model can be used to identify the onset of major flight activity of Etiella moths. 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 first reaches 351 is the date to commence in-crop monitoring. No further temperatures need to be recorded after a value of 351 has been reached.

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 lentil field. Recommended action thresholds are 1-2 Etiella moths in 20 sweeps. Insecticide sprays applied to control native budworm early in the podding period may offer some control for Etiella if present. However, monitoring should re-commence no longer than a week after spraying.

For images of Etiella and more information, including instructions for the degree-day model, click here.