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Earth mites

We have now received several reports of redlegged earth mites (Halotydeus destructor) and blue oat mites (Penthaleus spp.) appearing in paddocks after hatching from their summer diapause eggs. Reports received to date have generally been of relatively low numbers of mites on roadside grasses, pasture paddocks or volunteer crop plants. In Victoria, both redlegged earth mites and blue oat mites have been sighted around Elmore and Koondrook, in the Northern Country district, at Werribee, in the Central district and near Colac and Beaufort in the Western district. Mites are also likely to be active in other areas of Victoria, and also in New South Wales, following recent cold weather and rainfall.

Both of these pests attack a wide variety of plant types including cereals, oilseeds, pastures and broad-leaved weeds. They feed by piercing plant cells and sucking out the contents, which results in silver or white patches. High mite populations can kill plants at emergence, when crops are most vulnerable to attack. Autumn insecticide sprays for redlegged earth mites and blue oat mites should ideally target mites 2-3 weeks after emergence. This provides time for the majority of diapause eggs to hatch, but should be before the second-generation eggs have been laid. Be aware, continual monitoring of mite populations is needed and some damage to emerging plants may have already occurred by the time sprays are applied.

Redlegged earth mites and blue oat mites are up to 1 mm in length with a globular shaped dark body and eight red legs. Blue oat mites can be distinguished from redlegged earth mites by the presence of a characteristic orange-red mark on their back. Redlegged earth mites have a completely black coloured body. Another notable characteristic is that redlegged earth mites are often found feeding in aggregations of up to about 30 individuals, whereas blue oat mites tend to feed in small groups or singularly. Before deciding on the most appropriate control measure, ensure the correct mite species has been identified.

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