Tip Top Bio-Control Technical Bulletin
Two-spotted spider mite (Tetranychus urticae), European red mite (Panonychus ulmi), Spruce spider mite (Oligonycus ununguis), Southern red mite (Oligonychus ilicis).
Stethorus is a specialized spider mite predator in the lady beetle family. Adults are tiny, 1.5mm (1/10 inch) long, dark brown to black, oval beetles with brownish yellow antennae, mouthparts and legs. The larvae are slow-moving, gray, with conspicuous legs. They move from plant to plant on leaves. Eggs are yellowish ovals, laid singly in or near mite colonies. Adult beetles can fly and have an unusually good ability to find small infestations of spider mites.
Stethorus are shipped in small containers of 100 adults. They are shipped in shredded paper or other packing material to provide protection; mortality in these containers should be less than 10%. Once the beetles warm up they become active immediately and should be released into the spider mite infested areas as soon as possible. If necessary, beetles can be stored for a few days at 10° – 16°C (50°-61°F), but longer storage will reduce egg laying and adult life span.
Release a minimum of 100 adults per “hot spot”, or 10 adults per infested plant, weekly, for 3-4 weeks.
General Introduction Rate: Release a minimum of 100 adults per “hot spot”, or 10 adults per infested plant, weekly, for 3-4 weeks.
Greenhouse cucumbers, peppers and Interior Plantscapes: Low Rate: use general rate (above) or 0.5 beetles/m. sq., bi-weekly for 3 weeks. Moderate Rate: 100 Stethorus/mite “hot spot”, or 3-4 beetles/ m. sq., weekly until established in all infested areas.
The complete life cycle takes 14 to 20 days at 21° – 26°C (70-80 F). Female beetles lay 3 – 13 eggs per day. Over their long life span (up to 2 years) females can lay over 1000 eggs. Females must eat 20 – 40 spider mites per day to initiate and sustain egg laying. Larvae feed for 10-14 days. A single larva can consume 240 spider mites as it develops from egg to adult. Older larvae migrate down the plant to pupate and 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 and 10 adult mites per day. If food is scarce, they will also feed on other small arthropod eggs, aphids, nectar and pollen and will cannibalize their own species.
Best control of spider mites is achieved when Stethorus is used along with predatory mites. Use care when removing leaves from infested plants. Keep any leaves with Stethorus pupae in the greenhouse one week or until adult beetles have emerged. The pesticide fenbutatin oxide (Vendex ) can be used with Stethorus for additional control of spider mites if “hot spots” develop. It does not harm Stethorus, but avoid over-spraying, which reduces the predators food supply and their ability to reproduce. Spreader-stickers, supreme oils and soaps are harmful to beetles contacted by the spray, but have little residual activity.