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Biological control

Coccinellids have been valued in biological pest control, as they prey on agricultural pests such as aphids and scale insects. Their importance in controlling pests was noted as far back as 1814 in England. Their efficiency can vary: sometimes they have a relatively small effect on aphid populations; at others they cause significant seasonal declines.

Several species have been introduced to areas outside their native range; the first being the vedalia beetle, Novius cardinalis. The larva of the species was introduced to California in 1887 from Australia, to protect citrus trees from cottony cushion scale. The project was markedly successful, costing $1,500 in 1889, making it "a textbook example of the great potential of classical biological control as a tactic for suppressing invasive pests." The beetle was then used in 29 countries, again with success; reasons for this include its high prey specificity, fast development, multiple generations each year, efficient discovery of host patches, and larval development completed on a single host insect.

There have been many further attempts to use ladybird species against pests, with varying degrees of success. Scale insect-eating coccinellids have been more successfully used than aphid predators. Out of 155 deliberate introductions meant to control aphids by the year 2000, only one was deemed to be "substantially successful". This is due to aphid-eating species being fast-breeding, generalist and voracious, and thus difficult to control.