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Earth mites

Agronomist, David Ryan (Independent Agronomy Services), has reported very high numbers of redlegged earth mites causing damage to a canola crop north of Ballarat, in the western district of Victoria. A high number of mites were observed across the paddock soon after crop emergence, which was subsequently sprayed with an insecticide. This provided good control, but the mites have now moved back into the crop from an adjacent pasture paddock. Despite being at the 4-leaf stage, considerable feeding damage has occurred, characterised by typical silvering of the plant foliage. In some areas, well over 50 mites were observed feeding on a single leaf. It is quite common to see redlegged earth mites feeding in large aggregations.

Agronomist, Philip Stoddart (Landmark), reports high numbers of blue oat mites in a pasture/lucerne paddock north of Mudgee, in the Central Tablelands district of New South Wales. The mites have caused considerable damage to pasture plants, particularly to plantain. The paddock has been in pasture for several years. Philip says the high population size warranted insecticide control. Agronomist, Kate Wilson (AGRIvision Consultants), reported very high numbers of blue oat mites attacking two canola paddocks near Hopetoun, in the Mallee district of Victoria. Despite these paddocks being sprayed with insecticides in early June, Kate says considerable numbers are now present and causing damage. Large patches of crop have been completely destroyed due to the extent of mite feeding. Kate cannot recall seeing blue oat mites in such high numbers previously.

Redlegged earth mites (Halotydeus destructor) and blue oat mites (Penthaleus spp.) are about 1 mm long 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. Before deciding on the most appropriate control measure, ensure the correct mite species has been identified. These species differ in many aspects of their biology, including tolerance levels to insecticides. For assistance with identification download the GRDC Back Pocket Guide - Crop Mites.

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