Native to North America, Stethorus punctillum is a tiny (1.5 mm), oval, convex, shiny black lady beetle, covered with sparse, fine yellowish to white hairs, and is a predator of plant-feeding mites, particularly spider mites such as the European red mite and the two-spotted spider mite, and especially the eggs.
Stethorus larvae and adults consume all stages of spider mites. Adult beetles can fly and have the ability to find small spider mite clusters. Adults consume 50 to 100 mites and mite eggs per day and large larvae can devour up to 8 mites per hour, and can quickly impact an outbreak of spider mites.
When combined with other biological control agents such as predatory mites, Stethorus can improve the management of a variety of pest mites in interior plantscapes, greenhouses, and nurseries. Stethorus is more mobile than predatory mites but take longer to establish, so releases of predatory mites (N. californicus, N. fallacis, M. longipes, G. occidentalis, P. persimilis) should also be made into mite infested areas.
Release Stethorus at the first sign of spider mites.
Optimum conditions are moderate to high temperatures of 67-90øF (16-35øC), but they are known to survive temperatures over 100øF in field crops. They will remain active and feed at lower than optimum temperatures, but will not fly at temperatures below 54øF.
100 spider-mite destroyers may be enough to maintain a colony in a small private orchard or greenhouse, as they reproduce well, but field crops, commercial orchards and greenhouses may require augmentative releases. Stethorus is an important and frequent predator of spider mites in fruit orchards.
Release a minimum of 100 adults per hot spot, or 10 adults per infested plant weekly for 3-4 weeks.
Release adult beetles into mite infested areas and look for signs of reproduction (larvae, pupae, and adults) after four weeks. Two months after the first introductions, all stages of Stethorus should be present. Watch for small grey larvae and pupae on the undersides of leaves in areas with visible spider mite damage. Use care when removing leaves from infested plants. Keep any leaves with Stethorus pupae until adult beetles have emerged.
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