Blue oat mites

Agronomic consultant, Luke Maher (AGRIvision Consultants), has reported a control failure involving blue oat mites (Penthaleus spp.) near Swan Hill, in the Mallee district of Victoria. A canola paddock was treated with alpha-cypermethrin, but Luke says mites were still present and causing significant feeding damage over a week later. The affected paddock was re-sprayed with omethoate and appears to have provided adequate control. The paddock has been in crop for several years, but is unlikely to have experienced a high number of insecticide applications in the past.

There are three pest species of blue oat mite that differ in their biology, but to the eye look identical. The species responsible for these control failures was not identified, although it is likely to be Penthaleus falcatus. This species is relatively rare and favours canola crops, but will also attack cereals, pastures and even broad-leafed weeds. Importantly, this species has a significantly higher tolerance than other blue oat mite species and the redlegged earth mite to a range of registered pesticides.

High numbers of P. falcatus have also been observed attacking a canola paddock north of St. Arnaud, in the Wimmera district of Victoria. The damage was very severe in some places, with entire areas (some patches >30m in diameter) completely eaten out. Typical feeding damage, characterised by whitening/silvering of the leaves, could be easily observed, along with stunting of some cotyledons. 

Blue oat mites are similar in appearance and are often mistaken for redlegged earth mites. They also have similar life-cycles, however blue oat mites and the redlegged earth mite differ markedly in their biology and require separate management strategies. Blue oat mites can be distinguished from other mites by their blue-black coloured body and characteristic red mark on their back. Click here for images of blue oat mites and refer to PestFacts Issue No. 2 for further information.