Blue oat mites

Blue oat mites (Penthaleus spp.) have hatched following good autumn rains in many parts of Victoria and NSW. In Victoria, reports have come from the Wimmera, North Central and Western districts. Matt Hincks (NuFarm) says blue oat mites are also widespread in the Northern Country, attacking a variety of plants, including clovers, cereals and canola. Consultant, Ian Cocking (AGRIvision Consultants), reports blue oat mites are present in parts of the southern Mallee, in Victoria. It is likely that blue oat mites have hatched in other regions, such as Gippsland which has received good early rainfall. Agronomist, Glenn Shepherd (IMAG Consulting), has reported blue oat mite hatchings around Dubbo, in the Central West Slopes and Plains district of NSW. Agronomist, Tim Wright (AGnVET Services), has also reported mites active in pasture and emerging canola crops near Forbes, in the Central West Slopes and Plains district of NSW.

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 NSW. Blue oat mites can be distinguished from other mites by their blue-black coloured body and characteristic red mark on their back.

Chemical spraying of paddocks during the spring prior to the cropping year (as for redlegged earth mite control), is not an effective strategy for controlling blue oat mites. Instead, target these 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. Several of the latest reports suggest that the damage caused by emerging mites this season may be negated by the vigorous plant growth due to the good autumn rains and warm weather conditions.

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.