Two-spotted mite

Two-spotted mite damage to banana

Two-spotted mite predator

This mite is also known as a spider mite.

Scientific name

Tetranychus urticae

Description of adult

Adults are usually less than 0.5mm long with 8 legs, and their spider-like appearance can only just be seen with the naked eye. Under a x10 hand lens, the active form appears translucent or sometimes greenish with two conspicuous black spots on the body.

Immature stages

The clear, spherical egg is followed by 3 immature stages that are similar to the adult stage. All stages of the life cycle occur together, mostly near the veins of the underside of leaves.

Life history

The mite spends winters either as an orange, inactive, fertilised female in debris or as the active two-spotted form, breeding on other leafy hosts. The life cycle can be completed in 1–4 weeks, depending on temperature, and there are many overlapping generations each year. Populations increase rapidly in hot dry weather.

Distribution

Throughout Queensland.

Host range

The two-spotted mite has a wide host range, comprising

• broadleaved weeds, grasses
• crop plants such as strawberries, stonefruit, apples, pears, beans, tomatoes, cotton, bananas and papaya
• ornamentals such as roses.

Damage

Damage is minor and infrequent. The appearance of mites is often an indication of excessive insecticide use. Insecticide kills the biological control agents, such as predatory lady beetles and mites.

When mites feed, they suck the contents out of individual plant cells. The feeding can cause extensive leaf, flower and fruit damage. Leaf damage is distinguished by the development of yellow mottled or stippled areas, particularly on the underside of leaves. Damage first appears near the main leaf veins.

In some strawberry varieties, the feeding of two-spotted mites can result in reddening of the leaves.

Control

Examine 1 young, fully expanded leaf on 5 adjacent trees at each of 6 widely spaced locations throughout each 0.5ha of crop. Apply a miticide spray if mite damage and mites are present on 50% of the leaves and predators are not present.

Biological

Predators of mites, particularly the small black lady beetle Stethorus spp. and the predatory mites Amblyseius spp. and Phytoseiulus persimilis, usually control two-spotted mite infestations. Predatory mites are not common in the tropical conditions of North Queensland. Avoid unnecessary pesticide sprays that will destroy predators.

Chemical

Direct the chemical at the undersides of the leaves. One effective application should be sufficient. Avoid spraying in hot weather when chemical injury to leaves and fruit could occur.

Check the Australian Pesticides and Veterinary Medicines Authority database for chemicals registered or approved under permit to treat this pest on the target crop in your location. Always read the label and observe withholding periods.