Balaustium Mite

Balaustium medicagoense

Family: Erythraeidae

Order: Acarina

Names:

Medicagoense refers to Lucerne or Medicago sativa because the mite is often feeds on Lucerne and other legumes.

Description:

Red brown body to 2 mm with 8 orange legs with distinctive foot pads. Larger than similar mites when fully grown but young ones can be misidentified as bryobia mite.

Adult - Looks similar to Redlegged Earth Mite with a grey to reddish body with short hairs and may grow to twice the size. Juveniles have orange to dark red bodies.

Colour - Grey to red with red legs.

Body - Greyish to red. Rounded. Up to 2 mm long. Short stout hairs on the body can be seen with a hand lens.

Wings - None.

Mouthparts - Sucking.

Antennae - None

Legs - Red. 8 on adults, 6 on nymphs.

Head -

Thorax -

Abdomen -

Egg -

Habits -

Caterpillar - The eggs hatch into nymphs that look like small adults but only have 6 legs.

Biology:

They probably reproduce asexually.

Glands behind the eyes exude a viscous red fluid which is spread over the body by the body hairs and this provides some protection from predators.

Life Cycle:

Over-summering eggs hatch after rain. This can be in summer time as they have little temperature dependence. The new nymphs are orange and only have 6 legs. Adults have 8 legs. It takes 5-6 weeks from hatching to the adult stage and their may be several generations per year. They require continuous green plant material to survive.

Generally found from March to December with peak numbers in spring.

Habitats:

They tend to be worst on areas with a history of Capeweed.

Origin and History:

Distribution:

Widespread. Damage is most often reported in the cooler southern agricultural areas.

Damaging infestations have been reported from Narrogin to Esperance in WA. Eyre peninsula in SA and Central Victoria.

Damage Symptoms:

Whitening or silvering of leaves.

Bleached and dead tips on cereal leaves.

Canola cotyledons become distorted, cupped and leathery after attack.

Significance:

Symptoms of damage on plants are usually whitening or silvering of the leaves. Mites suck the sap from young soft tissue. They are rarely a problem on continuously cropped paddocks

Beneficial:

These mites are often predatory and may help control other mites such as Clover Bryobia Mite.

Detrimental:

Usually found in pasture.

Damaging numbers may occasionally occur in cereals, lupins and canola.

Management and Control:

Control early emerging weeds and grasses in cropping paddocks to reduce the build up of mite numbers and size. In most cases crops will not require spraying unless they are following pasture where significant populations were present. Check weeds (especially Capeweed) for mites and add an insecticide to the pre plant spray if necessary. Check crops soon after emergence and if there are more than 10 mites per plant then spraying could be warranted.

Alpha cypermethrin, cypermethrin and endosulfan at high rates have provided good control.

Fipronil (e.g. Cosmos) and imidacloprid (e.g. Gaucho) as seed dressings sometimes provide enough suppression to prevent yield loss.

Chlorpyrifos, dimethoate, omethoate and phosmet provide little control. Esfenvalerate also appears to provide little control.

Thresholds:

Appear to be around 30-40 mites per seedling for Canola and cereals.

Related Species:

Redlegged Earth Mite (Halotydeus destructor) has a dark or black body with red legs.

Blue Oat Mite (Penthaleus major) has a red spot on its back.

Balaustium Mite (Balaustium medicagoense) has short hairs on their body.

Clover Bryobia Mite (Bryobia praetiosa) has very long front legs.

Similar Species:

References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991)

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185.

Avidov, Z. and Harpaz, I. (1969) Plant Pest of Israel. Israel University Press. P

Micic, S. (2009) Pers Comm.

Micic S, Hoffmann AA, Strickland G, Weeks AR, Bellati J, Henry K, Nash MA, Umina PA (2008). Pests of germinating grain crops in southern Australia: an overview of their biology and management options. Australian Journal of Experimental Agriculture 48, 1560-1573.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.