Unusual weevils

Agronomist, Tim Condon (Delta Agribusiness), has reported significant issues with weevils attacking a cotyledon canola crop, north west of Gundagai, in the South West Slopes district of New South Wales. A large part of the crop has been completely eaten out by adult weevils, and required re-sowing. The crop was sown into wheat stubble, and has not previously experienced issues with weevils. Tim says the paddock has been continuously cropped for many years.  

These weevils have been identified by Rolf Oberprieler (CSIRO Ecosystem Sciences) as Atrichonotus sordidus, sometimes referred to as the ‘Flores weevil’. The species is native to Argentina, and rarely observed in Australia. It has been recorded in New South Wales and the Australian Capital Territory, but not elsewhere in Australia. There is very little known about the biology of the Flores Weevil. Adults and larvae are thought to feed on a wide range of legumes, especially clovers, and other plants. In New Zealand, this weevil has been recorded as severely damaging pastures and lucerne.

Tim reports that very high numbers of weevils have been observed, estimating densities well above 250 adult weevils per square metre. The canola seed was treated with imidacloprid, however this does not appear to have offered any substantial control. Tim says a border spray of bifenthrin applied prior to crop emergence has provided good protection of canola seedlings within these parts of the paddock.   

Click here for images of Flores weevils. Adults are small, round weevils with a broad snout. They are light greyish-brown in colour with darker brown patches on the thorax. If you observe these weevils attacking crops, please send your reports directly to us. We would like to determine whether or not this is an isolated situation.