Balaustium mites

We have received more reports of Balaustium mites (Balaustium medicagoense). Consultant, Simon Mock (Clovercrest Consulting), has reported moderate-high numbers of Balaustium mites attacking emerging canola seedlings in a paddock near Bordertown, in the Wimmera district of Victoria. Simon says typical feeding damage characterised by cupping and leathering of cotyledons can be easily observed. Researcher, Aston Arthur (University of Melbourne), reports that Balaustium mites have been observed in numerous pasture paddocks in the Western district of Victoria. Aston says Balaustium mites are typically present in highest numbers in May and June, and tend to decrease after this time (peaking again in spring).

There are currently no chemicals registered for the control of Balaustium mites. In addition, Balaustium mites are more tolerant to a range of insecticides compared with other mites. Simon reported that the paddock near Bordertown was sprayed with 200 ml/ha of alpha-cypermethrin two weeks ago but mite numbers were still quite high. This highlights the difficulties Balaustium mites can present and the importance of correctly identifying mites before deciding on control.

Balaustium mites reach about 2 mm in length, which is twice the size of other earth mite species. They also have distinct ‘pad-like’ structures on their front legs and move slower than redlegged earth mites and blue oat mites. They have a rounded dark red/brown coloured body and red legs similar to other pest mites, however they have distinct short stout hairs covering their entire body giving them a velvety appearance. Early control of late-summer weeds is probably the most appropriate option for preventing Balaustium mite problems. Reports indicate that crops sown into paddocks with a pasture history and high levels of broad-leaved weeds will be most at risk from damage.

For further information about Balaustium mites, refer to PestFacts Issue No. 3.