Bryobia mites

Large numbers of Bryobia mites have been observed around the Lockhart area, in the Riverina district of New South Wales. Agronomist, Elissa Strong (DeltaAg), has reported finding Bryobia mites across many canola paddocks that vary from early cotyledon to the 2^nd leaf stage. Signs of feeding damage are evident, which is characterised by whitish-grey spots and feeding trails on the upper surface of cotyledons and leaves. Elissa says the highest numbers of mites were observed during the warmer parts of the day. This is quite typical for Bryobia mites; they are most active when conditions are warmer, and difficult to detect during early mornings or in wet conditions.

Grower, Mark Day, reports finding Bryobia mites attacking several emerging canola crops near Lockhart. Mark says Bryobia mites were also problematic on his property last year. Often called the ‘clover mite’, Bryobia mites (Bryobia spp.) are an important pest of clovers, canola, wheat and lupins. Although Bryobia mites can be found all year, they prefer the warmer months from spring to autumn, and their population naturally declines over winter. The dry, mild weather experienced across much of eastern Australia this autumn, has provided optimal conditions for Bryobia mites.

It is recommended that growers across northern Victoria and southern NSW monitor paddocks closely, especially if moisture remains sub-optimal and emerging crops remain stressed. Look for mites and evidence of feeding damage on newly established crops and clovers. Unlike many other species of mites, which spend a lot of time on the soil surface, Bryobia mites are mostly found on the lower and upper leaf surfaces of plants. Researcher, Garry McDonald (cesar), has reported finding Bryobia mites in a lucerne paddock near Werribee, in the Central district of Victoria. Bryobia mites have also been collected near Donald, in the Victorian Wimmera.

It is important to distinguish Bryobia mites from other mite species before deciding on control options. If chemicals are required, application rates need to be higher than for other pest mites, such as redlegged earth mites and blue oat mites. This is because Bryobia mites have a higher natural tolerance to some chemicals. Agronomist, Warwick Nightingale (DeltaAg), reported a recent control failure in an emerging canola crop near Lockhart. In this case, bifenthrin was applied at the recommended field rate, however Bryobia mites were still present in high numbers 5-7 days post-spraying. Also note that insecticide seed treatments may not be effective against Bryobia mites. Elissa says the vast majority of canola crops around Lockhart are sown with insecticide dressings, however many paddocks are still being treated with a foliar application to control Bryobia mites.

Bryobia mites are less than 1 mm long with a fawn-orange coloured body and orange legs. Bryobia mites can be distinguished by their long forelegs, which are about 1.5 times their body length. Click here for further information on Bryobia mites, or alternatively you can download the GRDC Back Pocket Guide - Crop Mites.