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Ministry of Agriculture, Food and Rural Affairs

Stethorus/Spider Mite Destroyer

Coccinellidae

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Beginner

Scientific Names
Stethorus punctum punctum (LeConte) and Stethorus punctillum Weise

Identification

  • Both species are lady beetles.

Eggs:

  • White, oval and less than 0.5 mm long, and turn blackish just before the larvae emerge.
  • Laid singly.

Larvae: 

  • 2 mm in size, gray to blackish and is covered with short, branched hairs.
  • As the larva matures it becomes reddish, at first on the edges of the body and eventually entirely.

Pupae:

  • Black and flattened.
  • Somewhat pointed on the posterior end.
  • Entire body covered with yellow hairs.

Adults: 

  • Small (1.5 mm) shiny black beetles that are covered with sparse, fine yellowish to white hairs.
  • This is the lifestage seen most frequently in orchards.

Often Confused With
N/A

Interaction With Host
Both species described above fill a similar role as biological control agents.  Stethorus punctum can be found feeding on spider mites in a variety of crops including fruit orchards, and strawberry fields.  There are 2-4 generations of S. punctum each year.
Peaks in larval activity are dependent upon mite populations. There are usually three overlapping generations per year. The total time for development from egg to adult is 23 days.  Adults feed for an average of 25 days before beginning to lay eggs.
Period of Activity
Tight cluster through late summer.

Insects Attacked
Larvae and adults are important predators of European red mite and the twospotted spider mite (all life stages).

Monitoring and Management
S. punctum is one of the most important and frequently seen predators of spider mites in apple orchards. Beetles consume all stages of mites; adults can consume 75 to 100 mites per day and large larvae can devour up to 75 mites per day, so they quickly lessen an outbreak of spider mites.
Adults are easy to see with the naked eye, and are frequently tapped out onto tapping trays when monitoring for mullein bugs and other beneficial insects.  

Advanced

Scientific Names
Stethorus punctum punctum (LeConte) and Stethorus punctillum Weise

Identification
S. punctum punctum is a native species that has been displaced in many fruit orchards in Ontario by S. punctillum, an introduced species that it very closely resembles. 
Both species are lady beetles.

Eggs: Eggs are white, oval and are less than 0.5 mm long, and turn blackish just before the larvae emerge.  Unlike many other lady beetle species that are laid in egg masses, the eggs of Stethorus spp. are laid singly.

Larvae:  The mature larva is 2 mm in size, gray to blackish and is covered with short, branched hairs.  As the larva matures it becomes reddish, at first on the edges of the body and eventually entirely.

Pupae: The pupae are black and flattened, somewhat pointed on the posterior end, with the entire body covered with yellow hairs.

Adults:  Adults are small (1.5 mm) shiny black beetles that are covered with sparse, fine yellowish to white hairs. This is the lifestage seen most frequently in orchards.

Often Confused With
N/A

Interaction With Host
Both species described above fill a similar role as biological control agents. Stethorus spp. can be found feeding on spider mites in a variety of crops including fruit orchards, and strawberry fields. Stethorus spp. overwinter in the adult stage beneath leaves under fruit trees and in other protected habitats near the orchard (fence rows or adjacent woodlots). Adults begin to emerge at the tight cluster stage of apple development with peak emergence from the pink to bloom. Emergence is usually complete by the petal fall stage, and adults remain active in the orchard until September to late October.

Egg laying occurs from May to mid-August, with most eggs being laid on the undersurface of the leaf close to the primary leaf veins.   The larva emerges after approximately 5 days, and passes through four larval stages in about 12 days (depending on temperature), feeding on all stages of mites. The mature larva fastens itself to the leaf and pupates.
Peaks in larval activity are dependent upon mite populations. There are 2-4 generations of S. punctum each year. There are usually three overlapping generations per year. The total time for development from egg to adult is 23 days.  Adults feed for an average of 25 days before beginning to lay eggs.

Period of Activity
Tight cluster through late summer.

Insects Attacked
Larvae and adults are important predators of European red mite and the twospotted spider mite (all life stages).

Monitoring and Management
S. punctum is one of the most important and frequently seen predators of spider mites in apple orchards. Beetles consume all stages of mites; adults can consume 75 to 100 mites per day and large larvae can devour up to 75 mites per day, so they quickly lessen an outbreak of spider mites.
Adults are easy to see with the naked eye, and are frequently tapped out onto tapping trays when monitoring for mullein bugs and other beneficial insects.   Adults are good fliers, and tend to concentrate in areas of the orchard where mites are plentiful and disappear when the mite population becomes low. There must be 2-5 motile mites per leaf to keep S. punctum in an orchard, and "pockets" of 8-10 mites per leaf are required for reproduction.

S. punctum is sensitive to the use of broad-spectrum insecticides.  For more information on the toxicity of pesticides to beneficial insects refer to OMAFRA Publication 360, Fruit Production Recommendations.