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Balaustium mites

Agronomist, Matt Coffey (Elders), reports that balaustium mites (Balaustium spp.) have been found in high numbers in two wheat crops near Yarrawonga, in the northeast of Victoria. Both crops are at the 3-5 leaf stage, and sown into paddocks that were pasture in 2007. Some feeding damage is evident, however due to the limited control options available (see below), Matt says the paddocks will not be sprayed. Under favourable growing conditions the plants should be able to outgrow the damage. There have also been several recent reports of balaustium mites attacking pastures in parts of central Victoria.

Balaustium mites 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 indicating that they can 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 coloured legs. Leaf damage symptoms can also help to identify different mite species. Redlegged earth mites and blue oat mites cause silvering of leaves, while balaustium mites cause cupping and leathering of cotyledons. Click here for images of balaustium mites.

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 with other mites.

It is important to correctly identify mite species and seriously consider non-chemical control methods for balaustium mites. Research is continuing 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 balaustium mites.

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