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Balaustium mites

Consultant, Tim Condon (Delta Agribusiness), has observed balaustium mites attacking several canola crops around Harden, in the Southwest Slopes of NSW. Tim reported that 3-4 mites could be seen per canola seedling, although numbers appeared to be greater on volunteer cereals and grasses within the affected paddocks. Tim is not aware of balaustium mites being a problem in these paddocks previously, which were all sown with insecticide-treated seed this year. Researcher, Aston Arthur (cesar) says balaustium mites have been present for several months in most parts of Victoria, with mite numbers recently building-up in many pastures and crops in the Mallee and Western district.

Balaustium mites (Balaustium spp.) have recently been identified as emerging pests within the Australian agricultural industry. The damage caused by these mites in Australia seems to have significantly increased in the last decade, with reports in WA indicating that they 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 insecticides registered for the control of balaustium mites. Further, balaustium mites are often reported to persist in the field following chemical applications aimed at other mite species. Recent trials have shown a significant difference in tolerance levels across mite species. cesar has found balaustium mites are more tolerant to a range of organophosphorus and synthetic pyrethroid chemicals compared to 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 indicate that crops sown into paddocks with a pasture history and high levels of broad-leaved weeds, especially capeweed, will be most at risk from mite damage.

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