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Bryobia mites

Agronomist, Heidi Gooden (Delta Agribusiness), has reported the widespread presence of bryobia mites (Bryobia spp.) in many canola crops around Wagga Wagga, in the Riverina district of New South Wales. Mites were found in high numbers over a 4-5 week period through May, during which the region received little or no rainfall. As most canola in the region had been sown in late April following some good rain, crops struggled during this extended dry period and some sustained significant damage. This warm, dry period provided ideal conditions for bryobia mite activity, as unlike most other earth mite species that prefer the winter months, bryobia mites are typically most active in autumn, spring and summer.

Heidi estimates that approximately one-third of the canola crops in the region were affected to some degree. In the worst affected paddocks there were patches where all plants had silvering and cupping on the leaves and cotyledons, which are typical signs of bryobia mite damage. Bryobia mites were reported in the Wagga Wagga area in PestFacts Issue No. 2, however the extent of the problem was not fully apparent. Heidi says there did not appear to be any clear pattern linking the affected paddocks, although triazine tolerant (TT) canola varieties appeared to incur greater damage.

Often called the ‘clover mite’, bryobia mites are less than 1 mm long with a fawn-orange coloured body and orange legs. They may attack clovers, canola, wheat and lupins, and in the field they can be easily misidentified as redlegged earth mites. Bryobia mites can be distinguished by their long forelegs, which are about 1.5 times their body length.

Click here for images of bryobia mites.

Bryobia mites can be difficult to control with pesticides, and they are often reported to persist in the field following chemical applications aimed at other mite species. Recent findings by cesar have found that organophosphates may provide better control of bryobia mites than synthetic pyrethroids. Heidi reports that omethoate was most commonly used when chemical control was necessary.

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