Mites

Mites are tiny (usually 1mm or less) arachnids that can cause significant damage when populations are high.

Scientific name

Tetranychus ludeni (bean spider mite)
Petrobia latens (brown wheat mite)
Penthaleus major (blue oat mite)
Paraplonobia spp. (peanut mite)
Halotydeus destructor (redlegged earth mite (RLEM))
Tetranychus lambi (strawberry spider mite)
Tetranychus urticae (two-spotted spider mite)

Description

  • Mites can be difficult to see without a hand lens.
  • Mites have oval-shaped bodies with 8 legs.
  • Colour varies with species.
  • Usually from <0.5mm to about 1.5mm.

May be confused with

Predatory mites

Distribution in Queensland

  • Widespread across Australia and favoured by hot, dry conditions.
  • Earth mites are less of a pest in Queensland than in southern states.
  • Spider mites are often an end of season pest, flaring when pesticide applications targeting other pests kill off predators that are keeping the mite populations in check.

Life cycle

Eggs hatch into six-legged larvae and usually develop through 3 nymphal stages. Egg to adult can be very quick (7 days for two-spotted mite), allowing populations to build rapidly.

Monitoring and thresholds

Mites can be difficult to see without a hand lens.

  • For mites that attack seedling crops, check from planting to early vegetative stages.
  • For spider mites, check the underside of older leaves with a hand lens.

Hosts

Most mites will attack a range of host species; some are specific to either grasses or broadleaf hosts.

Natural enemies

Predators include small predatory bugs, thrips, lacewings and ladybirds.

Predatory mites are available for innundative release, but are unlikely to be economically viable under broadacre conditions.

Damage

Adults and nymphs pierce and suck leaf cells, causing mottling and discolouration of leaves. Heavy infestations can result in leaf drop, yield loss, and even plant death.

Control measures

  • Control alternative host plants (weeds and volunteers) between seasons.
  • RLEM have developed resistance to synthetic pyrethroids in some regions.
  • CSIRO have developed a model (Timerite©) to predict the best spray date in spring to control RLEM the following autumn.
  • Grazing may help reduce pasture mite populations.
  • Regular irrigation reduces the risk of peanut mite damage.

More information