Print this page

Occidentalis (Typhlodromus occidentalis) - Two Spotted Mite/Red Spider predator

Target pests: Two-spotted mite (Tetranychus urticae), European red spider mite (Panonychus citri), bean spider mite (Tetranychus ludeni)

Occidentalis

Typhlodromus occidentalis is a predatory mite which primarily attacks spider mites but can also feed and survive on some species of rust mites. It originates in North America and was found in Australia in the 1960s. Organophosphate and carbamate-resistant strains were subsequently introduced for spider mite control in stone and pome fruit.

Occidentalis is delivered as mixed life-stages on green bean leaves. There are approximately 100 predators on each trifoliate leaf.

Life history and biology

Occidentalis life cycle
Click to enlarge life cycle

Typhlodromus occidentalis is a small, off-white, pear-shaped mite, about the size of a spider mite. Eggs are slightly larger that spider mite eggs and more oval. They are laid among spider mite webbing or on the leaf surface. Female mites lay approximately 50 eggs at a rate of 1-3 per day. These develop through a six-legged larval stage and two 8-legged nymphal stages to adulthood.

Males are smaller than females. Optimal temperature is 27-32°C, at which the life-cycle is completed in 7-8 days. They can tolerate temperatures >40°C, making them ideal for hot, dry inland areas.

In field crops and unheated situations they hibernate during the winter so can survive cold and persist over many seasons, so long as no harmful pesticides are used. In heated greenhouses they are active all year, and are useful around heating pipes in winter, and hot/dry areas in summer where Phytoseiulus persimilis will not persist.

Crop usage

Occidentalis is primarily used in pome and stone fruit orchards. It may also be used in field vegetables and greenhouse vegetables, strawberries and roses during the summer months as it tolerates low humidity and high temperatures, and is resistant to several miticides, organophosphate and carbamate insecticides.

Environmental preferences

Temperatures in the range 27-32°C and low to moderate humidity, between 40 and 80%. Temperatures in excess of 40°C can be tolerated.

Application information

Storage and handling: Occidentalis on bean leaflets should be distributed as soon as it is received and not stored. Leaflets should be separated carefully when distributing and held by the stem to handle.

Release method(s): Examine crop before distribution and flag or note infested areas for more effective treatment. In tree crops, place two trifoliate bean leaves every ~7 m in every second row, with additional predators in spider-mite infested areas. Treat the missed row in a second release 4 weeks later. Leaflets may be stapled to infested leaves or placed in the crotch area. In greenhouse crops, distribute most leaflets in known hot-spots and surrounding plants, with the remainder through the crop, particularly in hot dry areas preferred by spider mites.

Timing of application: Apply early in the season at the first sign of spider mite activity or release into known hot spots. A second release is recommended approximately 4 weeks after the first to ensure good establishment. In tree crops, releases over several seasons to ensure establishment may be required.

Release rates:

  • Tree crops: Release 25,000 predators per ha in two releases
  • Outdoor vegetables: apply 50,000 predators per ha throughout the crop, with extra in infested areas
  • Ornamentals and greenhouse crops: Apply 10/m2 evenly through the crop, plus an additional 20-30 predators per infested plant in hotspots.

Monitoring control success

Check undersides of leaves for pale predatory mites. They are often alongside leaf veins in the vicinity of spider mite colonies. Ideally, they should be present in all patches of spider mites. Good control should be achieved within 6-8 weeks. See ‘The Good Bug Book’ for more specific recommendations for tree crops.

Tips for best results

Occidentalis breed more slowly and eat fewer spider mites than Phytoseiulus persimilis, but they persist longer and tolerate hotter, drier conditions. For rapid control, use both species simultaneously in greenhouse crops, relying more on P. persimilis in autumn, winter and spring. See ‘The Good Bug Book’ for more specific recommendations for tree crops.

Quality control

Examine leaflets on arrival to ensure they are in good condition and hold active predatory mites. Two-spotted mite may be present in small numbers as food in transit.

Pesticide compatibility

Occidentalis tolerates many organophosphate and carbamate pesticides and is resistant to azinphos-methyl and carbaryl. Orchard miticides such as Apollo®, Omite®, Torque®, Pyranica® and Acramite® are also relatively safe to use, especially at IPM rates. Check side-effects charts for safety of other pesticides before using.

» More information

Technical resources

Typhlodromus technical sheet (212 kb)