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Blue oat mites

Agronomist, Greg Toomey (Landmark), reports finding very high numbers of blue oat mites (Penthaleus spp.) on the lower leaves of a post-flowering cereal crop north-east of Elmore, in the Northern Country district of Victoria. Approximately 30 mites were seen on each leaf and they had caused quite extensive ‘silvering’ damage to the base of plants. It is rather unusual to see such high numbers of mites causing damage at this time of year. Blue oat mites (and other earth mite species) are most problematic in autumn where they attack seedling pasture and crop plants. Once cereal, oilseed and pulse crops mature they become less palatable for mites and plants are usually able to withstand mite feeding. It is very unlikely that the mites will impact yield in the cereal crop near Elmore, and Greg says no control measures will be taken.

Blue oat mites are approximately 1 mm long and have a globular shaped dark body with eight orange-red legs. They have a characteristic orange-red mark on their back that can be used to distinguish them from redlegged earth mites. With temperatures warming up, it is likely that blue oat mites (and redlegged earth mites) will soon die out in most cropping regions and enter their over-summering diapause state. They will survive as desiccation and heat resistant eggs, before hatching and giving rise to the autumn generation next year. Blue oat mite numbers have declined substantially in the Mallee and Wimmera districts of Victoria in recent weeks.

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