Blue oat mites

Blue oat mites (Penthaleus spp.) have hatched in the cooler wetter regions of Victoria and southern New South Wales. Mark Harris (Rural Management Strategies), has observed blue oat mites in a number of cotyledon canola crops around Lockhart, in the South West Slopes of New South Wales. Consultant, Simon Mock (Clovercrest Consulting) reports finding blue oat mites on volunteer cereals in a paddock near Bordertown, South Australia. The paddock will soon be sown with oats, which is susceptible to blue oat mite attack, especially at establishment. Because of this, the paddock is likely to be sprayed with an organophosphate, such as omethoate or dimethoate. Blue oat mites have also been observed in several pasture and established lucerne paddocks near Beaufort, in Western Victoria. At the present time, the mites are still quite small and unlikely to be causing any significant 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, target blue oat mites 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 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.