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Dactylopius opuntiae
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Dactylopius opuntiae
Dactylopius opuntiae, also known as the prickly pear cochineal, is a species of scale insect in the family Dactylopiidae.
Dactylopius opuntiae was first identified by Cockerell as Coccus cacti opuntiae after he collected it from cactus plants in Mexico in 1896. Later, it was considered a synonym of Dactylopius tomentosus, and workers often referred to the same species by different names or used the same name for different species. De Lotto notes that it became common practice to call Dactylopius opuntiae a distinct wild cochineal insect from Dactylopius tomentosus, even though their identity and status were never fully resolved. Eventually, in 1929, the species was classified as Dactylopius opuntiae by Cockerell.
All species of the family Dactylopiidae have females with an oval-shaped body that is purple-red in color and covered in a white, cotton-like wax. This wax protects the body of the cochineal from heat, cold, and predators. Adult females are sessile and form colonies of up to a few thousand individuals of mixed age, creating conspicuous clusters of white wax all over the plant. Adult females of Dactylopius opuntiae produce red glucosidal hydroxyanthrapurin (carminic acid), which occurs naturally within their body. Morphologically, all Dactylopius species have truncate dorsal setae and clusters of quinquelocular pores associated with tubular ducts on the body of females, and no microducts and cellular anal rings bearing setae. Large, truncate, and rounded setae longer than the width at the base and numerous narrow ventral pores on the last three body segments distinguish Dactylopius opuntiae from all its congeners.
Dactylopius opuntiae follows a life cycle similar to that of other species in the genus, consisting of two nymphal instars before adult females and two nymphal instars, prepupa, and pupa before adult males. Its biology has been studied in various regions, both in the laboratory and the open field, with female and male cycles lasting 77 and 43 days, respectively, in lab observations, and an offspring sex ratio of 3.7:1 (females:males) in greenhouse conditions. Field studies have shown that the female life cycle lasts 40–180 days, while males usually complete their cycle in 35–52 days. The optimal temperature for development is 30 °C, but males cannot emerge from the cocoon or adult females lay eggs at 35 °C, while crawlers' survival is negatively affected. The species usually reproduces bisexually, but it can reproduce by parthenogenesis under particular circumstances, such as high temperatures, resulting in lower progeny production.
The ovoviviparous females lay eggs one at a time beneath their bodies, with hatching occurring within 0.25–6 hours. Male and female crawlers are similar in appearance, but males of the Dactylopius austrinus species have shorter and fewer filaments than females. After a period of active dispersal, the crawlers settle down on the cladodes, often near the mother, and colonies are established at the joints of the cladode-trunk, flower-cladode, or fruit-cladode. Various factors can hinder cochineal development, including temperature, rain, and resistance factors of host plants. High temperatures and mechanical action of rain can negatively affect younger instars' survival, resulting in high mortality. Studies have shown that the species produces 4-5 generations per year in the Americas and Australia, with five generations occurring in the warmest areas.
Dactylopius opuntiae is native to Mexico and neighboring countries in Central America but has been introduced to several other areas, including Australia, Algeria, Morocco, Israel, France, India, Kenya, Madagascar, Pakistan, South Africa, Sri Lanka, and the United States (California and Texas).
Like other members of Dactylopiidae, Dactylopius opuntiae is not affected by parasitoid wasps. In Mexico, its most commonly occurring predatory species have been found to be Leucopis bellula, Sympherobius barberi, and Laetilia coccidivora.
In South Africa, Dactylopius opuntiae was introduced in 1932 along with three other insect species to control the cactus. Dactylopius opuntiae cleaned 75% of the infested areas, including those with the highest levels of opuntia infestation. Subsequently, about 90% of the original 900,000 ha returned to sheep-rearing due to the success of the cochineal as a biological control agent. However, dense populations of prickly pear still exist in cold and rainy areas, which are less favorable to the development of Dactylopius opuntiae. Subsequent introductions of Dactylopius opuntiae inside the Kruger National Park in the mid-1990s failed to control Opuntia stricta, confirming the importance of matching particular biotypes of biocontrol agents and host plants for weed control. A new strain of the cochineal was introduced from Opuntia stricta collected in Australia in 1997 with encouraging results. The genotype of Dactylopius opuntiae which effectively controlled Opuntia stricta in South Africa was also introduced in Kenya, resulting in the reduction in flowering and fruiting, and leading to the death of the plants.
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Dactylopius opuntiae
Dactylopius opuntiae, also known as the prickly pear cochineal, is a species of scale insect in the family Dactylopiidae.
Dactylopius opuntiae was first identified by Cockerell as Coccus cacti opuntiae after he collected it from cactus plants in Mexico in 1896. Later, it was considered a synonym of Dactylopius tomentosus, and workers often referred to the same species by different names or used the same name for different species. De Lotto notes that it became common practice to call Dactylopius opuntiae a distinct wild cochineal insect from Dactylopius tomentosus, even though their identity and status were never fully resolved. Eventually, in 1929, the species was classified as Dactylopius opuntiae by Cockerell.
All species of the family Dactylopiidae have females with an oval-shaped body that is purple-red in color and covered in a white, cotton-like wax. This wax protects the body of the cochineal from heat, cold, and predators. Adult females are sessile and form colonies of up to a few thousand individuals of mixed age, creating conspicuous clusters of white wax all over the plant. Adult females of Dactylopius opuntiae produce red glucosidal hydroxyanthrapurin (carminic acid), which occurs naturally within their body. Morphologically, all Dactylopius species have truncate dorsal setae and clusters of quinquelocular pores associated with tubular ducts on the body of females, and no microducts and cellular anal rings bearing setae. Large, truncate, and rounded setae longer than the width at the base and numerous narrow ventral pores on the last three body segments distinguish Dactylopius opuntiae from all its congeners.
Dactylopius opuntiae follows a life cycle similar to that of other species in the genus, consisting of two nymphal instars before adult females and two nymphal instars, prepupa, and pupa before adult males. Its biology has been studied in various regions, both in the laboratory and the open field, with female and male cycles lasting 77 and 43 days, respectively, in lab observations, and an offspring sex ratio of 3.7:1 (females:males) in greenhouse conditions. Field studies have shown that the female life cycle lasts 40–180 days, while males usually complete their cycle in 35–52 days. The optimal temperature for development is 30 °C, but males cannot emerge from the cocoon or adult females lay eggs at 35 °C, while crawlers' survival is negatively affected. The species usually reproduces bisexually, but it can reproduce by parthenogenesis under particular circumstances, such as high temperatures, resulting in lower progeny production.
The ovoviviparous females lay eggs one at a time beneath their bodies, with hatching occurring within 0.25–6 hours. Male and female crawlers are similar in appearance, but males of the Dactylopius austrinus species have shorter and fewer filaments than females. After a period of active dispersal, the crawlers settle down on the cladodes, often near the mother, and colonies are established at the joints of the cladode-trunk, flower-cladode, or fruit-cladode. Various factors can hinder cochineal development, including temperature, rain, and resistance factors of host plants. High temperatures and mechanical action of rain can negatively affect younger instars' survival, resulting in high mortality. Studies have shown that the species produces 4-5 generations per year in the Americas and Australia, with five generations occurring in the warmest areas.
Dactylopius opuntiae is native to Mexico and neighboring countries in Central America but has been introduced to several other areas, including Australia, Algeria, Morocco, Israel, France, India, Kenya, Madagascar, Pakistan, South Africa, Sri Lanka, and the United States (California and Texas).
Like other members of Dactylopiidae, Dactylopius opuntiae is not affected by parasitoid wasps. In Mexico, its most commonly occurring predatory species have been found to be Leucopis bellula, Sympherobius barberi, and Laetilia coccidivora.
In South Africa, Dactylopius opuntiae was introduced in 1932 along with three other insect species to control the cactus. Dactylopius opuntiae cleaned 75% of the infested areas, including those with the highest levels of opuntia infestation. Subsequently, about 90% of the original 900,000 ha returned to sheep-rearing due to the success of the cochineal as a biological control agent. However, dense populations of prickly pear still exist in cold and rainy areas, which are less favorable to the development of Dactylopius opuntiae. Subsequent introductions of Dactylopius opuntiae inside the Kruger National Park in the mid-1990s failed to control Opuntia stricta, confirming the importance of matching particular biotypes of biocontrol agents and host plants for weed control. A new strain of the cochineal was introduced from Opuntia stricta collected in Australia in 1997 with encouraging results. The genotype of Dactylopius opuntiae which effectively controlled Opuntia stricta in South Africa was also introduced in Kenya, resulting in the reduction in flowering and fruiting, and leading to the death of the plants.
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