Bryobia mites

Bryobia mites (Bryobia spp.) have been found in several regions of southern NSW. Agronomist, Geoff Pitson (Geoff Pitson Consulting), has reported bryobia mites attacking several canola crops near Griffith, in the South West Slopes district of NSW. Geoff says these crops have experienced significant feeding damage, necessitating chemical control. Agronomist, Paul Parker (NSW DPI), has observed bryobia mites causing damage to a canola crop near Young, also in the South West Slopes district of NSW. Paul says the mites have caused typical feeding damage symptoms (characterised by a long trail of whitish-grey spots on the upper side of cotyledons and leaves) and retardation of seedlings. Bryobia mites have also been sighted in canola crops around Junee, says consultant, Tim Condon (Delta Agribusiness).

Bryobia mites are an important pest of clovers, canola, wheat and lupins. Often called the ‘clover mite’, bryobia mites are less than 1 mm long with a fawn-orange coloured body and orange legs. In the field they are often misidentified as the redlegged earth mite. Bryobia mites can be distinguished by their long forelegs which are 1.5 times their body length. Unlike most other earth mite species, bryobia mites are most active in warm conditions in autumn, spring and summer. These mites are generally found in low numbers and are unlikely to be problematic over the winter period.

Agronomist, Dave Eksteen (NSW DPI), has also observed bryobia mites causing damage to canola crops around Finley, in the Riverina district of NSW. Dave says numbers are fairly low and do not warrant control. Although the biology and pest status of bryobia mites is poorly understood, these reports serve as a reminder to be on the look out in newly established pastures and emerging crops. Dave also warns growers to be careful when applying insecticides after using Logran in spraying booms. Booms must be thoroughly cleaned to remove all residues, which Dave says, have recently been responsible for the yellowing and stunting of canola seedlings. 

Recent research indicates bryobia mites are significantly more tolerant to a range of registered chemicals than redlegged earth mites. Past experiences with bryobia mites in Western Australia reveal that alpha-cypermethrin is not effective, and Geoff has reported control failures this season with some synthetic pyrethroid insecticides and endosulfan. Initial findings by cesar indicate that organophosphates may provide better control than synthetic pyrethroids against bryobia mites, however, information on the registration status, rates of application and warnings related to withholding periods and residues should be obtained before making decisions on which pesticide to use.