Blue oat mites

Farm consultant, Tim Condon (Delta Agribusiness), reports finding high numbers of blue oat mites (Penthaleus spp.) south-east of Cootamundra, in the South West Slopes district of New South Wales. Up to 50 mites could be found per plant, in a paddock of emerging oats and ryegrass. Tim says there was ‘silvering’ damage on the leaves and the growth of plants had been severely reduced. Given the high numbers of mites and the damage sustained, omethoate has been applied to the affected paddock. 

Blue oat mites have also been reported by agronomist, Glenn Shepherd (IMAG consulting), in an early tillering wheat crop near Parkes, in the Central West Slopes and Plains district of New South Wales. At present, the mites are in low numbers and are quite small, indicating that they have only recently hatched from their over-summering eggs. Glenn says monitoring will continue with particular attention being paid to crops that are just emerging, as these are most susceptible to earth mite damage.

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 tolerance to pesticides, and require separate management strategies. Blue oat mites are the most abundant earth mites in many cropping and pastoral areas of Victoria, Tasmania and New South Wales. 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.

If chemical control is warranted, blue oat mites should be targeted within 2-3 weeks of 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 control 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.