The red dye, carmine, comes from the bodies of female cochineal insects, Dactylopius coccus. In Peru and the Canary Islands, these have for centuries been reared on prickly pear cactus plants, Opuntia ficusindica. The insect can only survive on varieties of this plant. With use of synthetic dyes for human consumption coming under increasing criticism, the demand for natural dyes is increasing.
In parts of southern Africa there are large, aggressive wild stands of prickly pear, but rainfall patterns and intensity make it impossible to grow the insects on plants cultivated in the open. Any rainfall washes insects from the plants and they do not survive. A new rearing method allows them to make use of the vast supply of healthy plants, according to Economic Botany (vol 4, pp 154-162, 1993). “Healthy, fully mature terminal [pads] are suspended from hooks inside large sheds (90 m2) after they have been seeded with crawlers (immature stages of the insect).” After three months in the summer to five months in winter, the mature females are harvested by placing the pad over a container and blowing compressed air over them. Some females are allowed to reproduce. All females are eventually dried at 60°C for two days before they are exported.
“Preliminary estimates are that annual production of dried cochineal insects for a rearing unit of 90 m2 will be 75 kg. Based on a world price of US $40 per kg, this represents a gross income of US $3,000.” They estimate that 34 rearing units could be maintained for every densely populated hectare of cactus.“
This work was done by Dr. H. G. Zimmermann, director of the Plant Protection Research Institute in South Africa (Agricultural Research council, Private Bag X134 Pretoria 0001, Republic of South Africa). He told ECHO that his research had to be stopped for lack of funding. The original research paper he sent us lists the following problems that still need to be solved. (1) 80% or more of immature crawlers are lost. (2) Optimum temperatures are not known. Also conditions leading to periodic excessive decay of pads are unknown. (3) Contamination of the insect population by D. opuntiae can be a problem. (This insect was brought into South Africa as a biological control of prickley pear cactus.)
ECHO Staff 1993. A New Rearing Method for Cochineal Insects. ECHO Development Notes no. 43