Californicus (Neoseiulus californicus) -
spider mite predator
Target pests: Primary: Two-spotted spider mite, Tetranychus urticae; bean spider mite, T. ludeni. Secondary: Eriophyid and tarsonemid mites e.g. rust mite, broad mite.
Neoseiulus californicus is a small, predatory mite which has a worldwide distribution but is particularly suited to warmer climates in North and South America, and in the Mediterranean. Californicus has been commercialised overseas for several years for use in both field and greenhouse crops. It is thought to be synonymous with Neoseiulus wearnei which was first described from ACT in 1987 and is now found in all states and territories. Biological Services has a strain collected after a prolonged heat wave in South Australia in 2009, from stone fruit crops after several toxic sprays were used for carpophilus beetle control. It was first commercialised in Australia in 2010 by Biological Services.
Californicus is supplied on bean leaves, or in a loose vermiculite-based medium containing 10,000 predatory mites. It tolerates a wider range of temperature and humidity conditions than either P. persimilis or N. cucumeris, and as more of a generalist than P. persimilis, can survive in the absence of its main prey, allowing it to be used preventatively. It is particularly tolerant of hot/dry conditions, and hardy to a range of pesticides.
Life history and biology
Californicus is <1 mm long, pear-shaped and buff to tan colour depending on food consumed. It is similar in appearance to N. cucumeris but slightly slimmer. Males are much smaller and darker brown, with females more numerous. The female lays oval, white translucent eggs singly on leaf undersides, often on leaf hairs or at the junction of veins. The eggs are larger than those of spider mites. They hatch after 1-2 days and pass through a 6-legged larval and two 8-legged nymphal stages to adulthood. The life-cycle from egg to adult is temperature dependent but in greenhouse conditions ranges from 4-10 days. Adult females live approximately 20 days and lay about 25 eggs at a rate of 2-3/day, beginning 2-3 days after maturity and laying them mostly within the first 10 days. Pollen, moulds, nectar and other small arthropods are used as a subsistence diet once two spotted mite is controlled. Californicus will persist in the crop even at low prey densities, and the predator population will not decline as rapidly as P.persimilis in the complete absence of two spotted mite.
Crop usage
Californicus is still being evaluated but it is anticipated that it will be a useful supplement to P. persimilis in all crops where spider mites are a pest and to N. cucumeris where eriophyid and tarsonemid mites are pests, because of its tolerance of extreme conditions. Neoseiulus wearnei can be used on a broad range of crops. It is primarily used in greenhouse production, but can also be used in field crops, particularly fruit tree crops and strawberries. Suitable crops include vegetables (capsicum, eggplant, cucumber), ornamentals (gerbera, chrysanthemum, rose), strawberry, raspberry and herbs. Survival on tomato is reduced by leaf hairs, requiring higher rates and more frequent introductions.
Environmental preferences
Californicus is a warm-temperate predator which tolerates extremes of high and low temperature and low humidity. It does not diapause so can be used year round. Its preferred temperature range has not yet been studied but it should be useful within a range of 15-38°C but can tolerate temperatures below 10°C and above 40°C.
Application information
Storage and handling: Californicus can be stored for 1-2 days at 10-15oC out of direct sunlight if necessary, but preferably should be placed in the crop as soon as it is received.
Release method(s): Apply evenly through the crop on foliage, with additional material at ends of rows or in hot, dry areas prone to spider mites. They should be released as soon as possible. For tall crops, apply to foliage and try to avoid material falling onto pathways and between bags and pots. To prevent wastage and reduce labour, future plans are for distribution through slow-release, water-resistant sachets hung from or over leaf petioles, as is common practice overseas.
Timing of application: Californicus is best used as a preventative treatment from early in the crop. Increase rates during hot dry weather and when spider mites are observed.
Release rates: Rates will vary depending on the crop and infestation level. Contact Biological Services for crop-specific recommendations. The following rates have been determined overseas for N. californicus. Preventative: 1-2/m2 every 2 weeks (2-3 applications). After spider mite detection: 4-6/m2 weekly for at least 3 applications. Control is not immediate, therefore, spot-treatment of two-spotted mites or other target pest mites in hot-spots with a low toxicity, short-residual pesticide is recommended to prevent migration through crop.
Monitoring control success
Examine crop at least weekly for spider mite colonies and presence of predators within the colony. White speckling visible on upper foliage may indicate an early infestation. Predators should be present on most leaves with spider mites. Use a 3x headband magnifier for quick scanning and a 10x magnifier for closer inspection.
Tips for best results
Use preventatively, before spider mites are observed in the crop, particularly in warmer months. Release close to known pest colonies, at the edges of visible damage as well as on damaged leaves. Californicus is best used to supplement P. persimilis during periods when this predator is less active (high and low temperatures, low humidity). Movement on tomato is impeded by leaf hairs so although Californicus consumes tomato russet mite, Aculops lycopersici, the numbers needed may be financially non-viable. Knock back any heavy spider mite infestations before releasing Californicus.
Quality control
Check at receival for small, brown, active mites using a 10x hand lens. Contact Biological Services if no activity is observed.
Pesticide compatibility
Californicus appears to have some resistance to pesticides and the original colony was collected from a field crop that had been regularly sprayed with organophosphate, carbamate and pyrethroid insecticides, however definitive studies have not yet been conducted. Overseas data for Neoseiulus californicus can serve as a guide but there may be significant differences between species and even strains of predator mites from different sources, depending on exposure history.
Technical resources
Neoseiulus technical sheet (121 kb)