Blue oat mites

Agronomist, Stuart Little (Cleanseeds P/L), has reported an outbreak of blue oat mites (Penthaleus spp.) attacking an oat crop near Bungendore, in the Southern Tablelands of NSW. Stuart says high numbers have been observed feeding on oat plants and large areas of the paddock are displaying a silvery appearance on the plant foliage; characteristic of mite feeding. Agronomist, Phil Stoddart (Landmark), reports large numbers of blue oat mites on pastures and a variety of crops around the Central Tablelands and Central Slopes of NSW.

Agronomist, Greg Toomey (Landmark), reports an outbreak of blue oat mites on oats near Rochester, in the Northern Country of Victoria. The affected crop has been sown into a paddock with a long pasture history. Agronomist, Murray Skinner (TP Sullivan P/L), has also reported outbreaks of blue oat mites around Dunedoo, north-east of Dubbo, NSW. The mites have been observed attacking cereal crops and pastures. Murray says numbers have increased dramatically following the recent rainfall received in the area. Additionally, there have been reports of blue oat mite numbers ‘building-up’ in the Wimmera and Western districts of Victoria.

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 plant host preferences. Blue oat mites are the most abundant earth mites in many cropping and pastoral areas of Victoria, Tasmania and NSW.

There are 3 pest species of blue oat mite which differ in their biology, but to the eye look identical. The species responsible for most control failures is 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. This highlights the importance of distinguishing earth mite species before implementing control strategies.

If you have control issues or outbreaks of blue oat mites, it is strongly recommended that samples are accurately identified. Specimens can be sent to Paul Umina for free identification. Although blue oat mites are commonly controlled using pesticides, non-chemical options are available. 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 blue oat mites. Weed control can also suppress the build up of blue oat mites during the growing season.