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Balaustium mites

Consultant, Simon Mock (Clovercrest Consulting) reports balaustium mites have been present within a canola crop in the Wimmera district of Victoria. The affected paddock had been sprayed with a synthetic pyrethroid as a bare-earth, but after spraying the mites were still present. Natalie Thornton (Elders) has found balaustium mites in a lupin crop, south of Ararat in western Victoria. The paddock was sprayed with an organophosphate, followed by a synthetic pyrethroid. Again, the mites were still present following applications. Balaustium mites have also been observed attacking barley around Geelong, Victoria.

Balaustium mites (Balaustium spp.) have recently been identified as emerging pests within the Australian agricultural industry. The damage caused by these pests in Australia seems to have significantly increased in the last decade, with reports in WA indicating that these pest mites cause extensive damage to cereal, canola and lupin crops.

Balaustium mites are often confused with other mite pests. Adults grow to be twice the size of a redlegged earth mite, about 2 mm in length. They have a rounded red-brown coloured body, densely covered with stout hairs, with orange-red legs.

Leaf damage symptoms can also help to identify different mite species. The redlegged earth mite and blue oat mites cause silvering of leaves, while balaustium mites cause cupping and leathering of cotyledons.

At present, there are no pesticides currently registered for the control of balaustium mites. Balaustium mites are often reported to persist in the field following chemical applications aimed at other mite species. Recent pesticide bioassays have shown a significant difference in tolerance levels across mite species. cesar has found balaustium mites are more tolerant to a range of organophosphates and synthetic pyrethroids compared with other mites.

It is therefore important to correctly identify mite species and seriously consider non-chemical control methods for balaustium mites. Research is continuing in both WA and eastern Australia to better understand the biology and control of this species.

Reports from WA indicate that crops sown into paddocks which a pasture history, with high levels of broad-leaf weeds, especially capeweed, will be most at risk from mite damage.

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