Stethorus punctillum

Stethorus punctillum

Descripton

Stethorus is a specialized spider mite predator in the lady beetle family. Adults are tiny, 1/10 inch long, dark brown to black, oval beetles with brownish yellow antennae, mouthparts and legs. Larvae are slow moving, grey 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. 

Target Pest

Two-spotted spider mite (Tetranychus urticae), European red mite (Panonychus ulmi), Spruce spider mite (Oligonychus ununguis), Southern red mite (Oligonychus ilicis). 

Life Cycle

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. A single larva can consume 240 spider mites as it develops from egg to adult. Older larvae migrate down the plant to plate 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 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 cannibalize their own species. 

Stethorus punctillum larva

Use in Biological Control

Research in Canada (Raworth 2001) has shown that Stethorus will become established and reproduce on spider mites in greenhouse pepper and cucumber crops. When combined with other biological control agents, such as predatory mites, Stethorus can improve the management of a variety of pest mites in greenhouses, interior plants capes and nurseries. 

Optimum conditions are moderate to high temperatures of 61-90°F. they may remain active and feed, but won't fly at temperatures below 54°F. 

Monitoring Tips 

Watch for small grey larvae and pupae on the undersides of leaves in areas with the earliest spider mite damage. After 4-5 weeks the first adult Stethorus should be found in areas with spider mites. Two months after the first introductions, all stages of Stethorus should be present in the oldest mite-infested areas. 

Product Information

Stethorus are sold in small containers of 100 adults. They are shipped in shredded paper or other packing material to provide protection; mortality on these containers should be less than 10%. 

Once the beetles warm up they become active immediately and should be released into spider mite infested areas as soon as possible. If necessary, beetles can be stored for a few days at 50-61°F, but longer storage without food will reduce egg laying and adult life span. 

Rates

In commercial greenhouses, release Stethorus preventively or at the first sign of spider mites. Increase or decrease these general rates as needed. 

100 adults /hot spot or

10 adults/infested plant, weekly for 3-4 weeks or

 1-2 beetles/m2

for Best Results 

Best control of spider mites is achieved when Stethorus is used along with predatory mites (P. persimilis, A. fallacis)

Use care when removing leaves from infested plants. Keep any leaves with Stethorus pupae in the greenhouse until adult beetles have emerged. 

Using Chemicals

The pesticide fenbutatin oxide 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. 

Spreaders-stickers, horticultural oils and soaps are harmful to beetles contacted by the spray, but have little residual activity. 

 

Content Courtesy of Applied Bio-nomics Ltd.