Stethorus punctillum - Spider Mite Destroyer
This small, (1/10 of an inch long) black predatory beetle feeds on all life stages of spider mites. Adults can fly, allowing them to locate spider mite colonies that are not accessible to predatory mites. Their yellow oval eggs are laid singly in or near mite colonies. Larvae are slow moving with conspicuous legs. Larvae and adults feed on all stages of spider mites. They can also feed on small arthropod eggs, aphids, nectar, and pollen. Stethorus prefer smooth leaved plants and can’t readily travel the hairy leaves of greenhouse tomatoes. These predatory ladybird beetles are best used in combination with predatory mites. Regular monitoring, in conjunction with cultural controls help insure the successful use of predatory mites, midges and beetles against spider mites.
Target Pest: Two-spotted spider mite (Tetranychus urticae), European red mite (Panonychus ulmi), Spruce spider mite (Oligonychus ununguis), Southern red mite (Oligonychus ilicis)
Release Rates and Instructions: Apply 0.5 - 1 per 10 square feet. Weekly applications should provide sufficient control of two spot spider mites in flower.
Optimal Environment: Optimum conditions are moderate to high temperatures of 67-90°F. They may remain active and feed, but will not fly at temperatures below 54°F.
Lifecyle: The complete life cycle takes 14-20 days at 70-80°F. Female beetles lay 3-13 eggs per day. Over their long life span (up to 2 years), females can lay over 1,000 eggs. Females must eat 20-40 spider mites per day to initiate and sustain egg laying. Larvae feed for 10-14 days, and a single larva can consume 240 spider mites as it develops from egg to adult. Older larvae migrate down the plant to pupate. Pupae are often found along leaf veins on the undersides of leaves. Adults emerge from pupae in 6-7 days. Both larvae and adult beetles feed on all stages of mites. Adults can eat over 50 mite eggs or 10 adult mites per day. If food is scarce, they will also feed on other small arthropod eggs, aphids, nectar and pollen, and will even cannibalize their own species.
Strategic Considerations: Best control of spider mites is achieved when Stethorus is used along with predatory mites (Fallacis and Persimilis). Use care when removing leaves from infested plants. Keep any leaves with Stethorus pupae in the greenhouse until adult beetles have emerged.