Dactylopius opuntiae (Cockerell)
Common name: Opuntia cochineal scale.
Geographical distribution: North America, Middle East, India, and Australia.
Host plants: Species of Opuntia with flat pads.
Morphology: Females and nymphs secrete and cover themselves with white waxy filamentous secretions. The body is broadly oval or rotund; dark purple, bright red (“carmine”) when crushed. The red crawlers are armed with long filaments on the posterior part of their abdomen.
Life history: Reproduction of this species is usually sexual, the sex ratio female: male being 1:1, but some parthenogenetic females also occur. Each female excretes an ovisac, into which it lays an average of 130 eggs. Some crawlers settle nearby, but most move to the highest point of the cladode to be wind-dispersed, their wax threads providing buoyancy. The females attach themselves to the plants and remain there for the rest of their lives. The short-lived males pupate to become winged adults.
Economic importance: The feeding of the scale induces yellow areas on the cladode within a few weeks, subsequently causing its drop. The pest is capable of killing small cacti within months, or a large cactus within two years. It is a major pest of cactus plantations in South America, and has recently invaded Israel. On the other hand, D. opuntiae was used for the biocontrol of invading cacti in Australia.
Mechanical methods: Attacked cacti that are still alive after two years should be removed, and the cochineal-infested cladodes destroyed.
Plant resistance: Some species of Opuntia, or clones thereof, are fully or partially resistant to the scale.
Chemical control: Several organic compounds have been applied against the pest, including neutral detergent concentrations, cassava starch, liquid wastes, terpenoids, mineral oils and neem, which was the most efficient. A pyrethroid and an organophosphate also provide control of the cochineal.
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