Mites are tiny (usually 1.5mm or less) arachnids that can be difficult to see without a hand lens but can cause significant damage when populations are high. Most mites will attack a range of host species; some are specific to either grasses or broadleaf hosts.

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.

Eggs hatch into six-legged larvae and usually develop through 3 nymphal stages. Adult mites have oval-shaped bodies with 8 legs. Colour and patterning can vary with species. Egg to adult can be very fast (7 days for two-spotted mite), allowing populations to build rapidly.

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.

Predators of mites include small predatory bugs, thrips, lacewings, ladybirds and predatory mite species.

Manage mites by controlling alternative host plants (weeds and volunteers) between seasons. 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. Regular irrigation reduces the risk of peanut mite damage. Grazing may help reduce pasture mite populations.

Leaf mites

Leaf mites are widespread across Australia and favoured by hot, dry conditions. Species of leaf mites include:

  • Bean spider mite Tetranychus ludeni
  • Broad mite Polyphagotarsonemus latus
  • Brown wheat mite Petrobia latens
  • Peanut mite Paraplonobia
  • Strawberry spider mite Tetranychus lambi
  • Two-spotted spider mite Tetranychus urticae

Earth mites

Earth mites prefer cooler conditions and are less of a pest in Queensland than in southern states. The most common species are:

  • Red legged earth mite (RLEM) Halotydeus destructor
  • Blue oat mite Penthaleus major
  • Balaustium mite Balaustium medicagoense
  • Bryobia mite Bryobia

Read more about earth mites at the IPM guidelines for grains website. Note that RLEM have developed resistance to synthetic pyrethroids in some regions.

Predatory mites

Several species of mites are predators of eggs and small insects, including pest mite species. While predatory mites are available commercially for innundative release; their economic viability will depend on your circumstances.

Examples of predatory mites include Phytoseiulus persimilis, Transeius montdorensis and Typhlodromus occidentalis.

Resistance surveillance of two-spotted mites

Resistance testing by NSW DPI in two-spotted mites (TSM) during the 2022/23 season confirmed that abamectin resistance remains stable at moderate levels in northern NSW with significantly lower levels than in the south of the state. There was very low resistance to propargite in all regions. However, diafenthiuron resistance was detected in several TSM populations from the Namoi/Gwydir valleys. In some cases, resistance was recorded at approx. 10% above baseline, a significant increase from previous seasons.

Further information