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Blue oat mite control failure

Agronomist, Peter Roberts (AGnVET Services), has reported a chemical control failure involving blue oat mites near Forbes, in the Central West Slopes and Plains district of NSW. The affected paddock is an emerging canola crop that was sprayed with dimethoate after suffering extensive feeding damage. A second insecticide has been applied, although it is still unclear whether this has provided adequate control. Peter says this paddock was sown to wheat last year and was pasture in 2005. This control failure follows several other reports involving blue oat mite control problems this season, and serves as a reminder that management decisions need to consider non-chemical options as well.

Blue oat mites are often mistaken for redlegged earth mites due to their similar appearance and sympatric life-cycle. 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. For images of blue oat mites, click here.

There are three pest species of blue oat mite which differ in their biology, but to the eye look identical. The species responsible for this control failure has been identified as 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 the redlegged earth mite and other blue oat mite species to a range of registered pesticides.

If you hear of any chemical control failure involving mites, please send your reports directly to Paul Umina and/or advise your local agronomist.

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