Blue oat mites

Agronomist, Mick Duncan (Northern Agriculture P/L), has reported finding blue oat mites (Penthaleus spp.) in various crops around Tamworth, in the North West Slopes and Plains district of New South Wales. Mick says the mites appear to have only recently hatched from their over-summering (diapause) eggs, as they are mostly small nymphs and have only been found in low numbers. At this stage chemical control is not necessary, however monitoring will continue with particular attention being paid to emerging pastures as these are particularly susceptible to earth mite attack. There have also been reports of blue oat mites in several emerging pasture and cereal crops around Bendigo, in Victoria’s Northern Country district, and in a pasture paddock near Winchelsea, in the Western district of Victoria.

Blue oat mites are often mistaken for redlegged earth mites due to their similar appearance and sympatric life-cycle. They 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.

If chemical control is warranted, target blue oat mites within 2-3 weeks of mite emergence. This approach should protect newly germinated seedlings, which are most prone to mite attack. Be aware, continual monitoring of mite populations is needed and some damage to emerging pasture and crop plants may have already occurred by the time sprays are applied.

A reminder, non-chemical options are available for blue oat mites. For instance, pasture and crop rotations can limit the need for any pesticide spraying in a given year. Crops such as chickpeas and some lentil varieties are generally poor hosts of earth mites. As with redlegged earth mites, weed control can suppress the build-up of blue oat mites during the growing season.

For further information on blue oat mites, refer to PestFacts Issue No. 2.