Today in THE FEATURED PLANT section we focus on how the prickly pear cactus (Opuntia ficus-indica), a plant native to the semi-arid habitats of Central America, ended up growing all over the world.

The prickly pear cactus

The prickly pear or indian fig cactus is a shrub very easy to identify by its fleshy, spade-shaped, greyish-green stems, covered with thorns and reddish fruits, which also fleshy and thorny, with a sweet, jelly-like pulp. If you don’t know it, you can find all the details in the factsheet available here.

In Europe it is cultivated especially in the Mediterranean area for food use and for use in gardening or to form protective living fences. Fast-growing and easy to propagate, it is highly resistant to drought, which has made it easy for it to escape from gardens and plantations and grow in the wild, where it has become invasive and competes with the native flora.

Although it is highly valued as food, the use for which the prickly pear was brought from its place of origin to almost every corner of the world is linked not to the plant itself, but to its insect pest: the cochineal (Dactylopius sp.).

Cochineal

Cochineal is a small sap-sucking insect that protects itself with a whitish, cottony wax when living on prickly pear blades. It produces carminic acid, a powerful reddish natural dye that is still widely used today in the food, cosmetics, textile and pharmaceutical industries. The dye used to produce the colour is known also as ‘cochineal’ (‘grana’ in Spanish) and is made from the dried females of Dactylopius coccus, the species of cochineal that produces the most amount of dye. Another species is Dactylopius opuntiae, the wild cochineal, which also produces the red dye, although not in quantity.

The color of desire

Capturing the vivid, saturated colours of nature has been a human obsession since ancient times. For centuries colours were obtained from plants, insects and molluscs, with blue, red and violet being the most prized shades due to their scarcity or difficulty in obtaining them. These colours became a symbol of power and nobility, and in past times sumptuary laws restricting their use to the wealthy classes were not uncommon.

Until the colonisation of America, red in Europe was obtained from madder (Rubia tinctorum), which root gave vivid and intense caldera and russet reds, always with slightly orange tones. Another much deeper red was obtained from kermes (Kermes vermilio, an insect pest of the kermes oak –Quercus coccifera-), which was scarce and extremely expensive due to the large number of insects needed to produce small quantities of dye.

The arrival in America at the end of the 15th century opened the door to a host of unknown and potentially interesting materials for the European colonisers. One of these was the carmine red that the indigenous peoples of Mexico produced from the “blood” of prickly pear cactus shovels: a much deeper colour than the madder red, and much easier to produce than kermes.

Let us introduce you some of the fascinating stories about the cochineal and the prickly pear cactus, all of them are explained in detail in the book A Perfect Red. Empire, espionage and the quest for the color of desire by Amy Butler Greenfield (2005, HarperCollins Publishers, New York).

A treasure that not everyone knew well

The Spanish government soon dictated protectionist and monopolistic policies to control the trade of all materials coming from its American colonies, and in particular, cochineal.

Thus, for centuries, cochineal became a prized and coveted resource for all European governments, who decided to undertake long and sometimes dangerous spying trips to bring prickly pear paddles infested with the insect to their countries, with the intention of cultivating them and no longer being dependent on the Spanish empire.

The whitish paddles travelled for long periods of time in poor conditions, hidden from the eyes of the Spanish administrators, and often arrived at their destination with all the insects dead, the journey being in vain and having to start all over again.

The limited success of these quests was partly due to the fact that in Europe cochineal was believed to be the seed of the plant (hence the name in Spanish “grana”=”seed”) rather than an insect. The best way to keep the insect alive during clandestine journeys was therefore unknown.

It was not until 1726 that a wealthy and learned Dutchman, who had lived in Spain, bet his colleagues to prove the nature of cochineal before four independent judges. And he succeeded thanks to his contacts with producers in Oaxaca (Mexico), the main producing area at the time, who knew perfectly well that the cochineal was an insect.

Despite this scientific advance, for Europeans, cochineal remained an almost unattainable dyeing material. Even Charles Linnaeus found it impossible to bring alive the insects to his own country, Sweden. A fervent advocate of self-sufficiency, he was obsessed with growing all kinds of tropical products in his country, and carmine was no exception. Only one of his disciples, in 1755, managed to transport a plant with live insects from Surinam to Sweden. By bad luck, when the prickly pear infested with cochineal arrived at Linnaeus’ greenhouse, he was not there, and it was received by one of his gardeners, who, not knowing that it was a treasure, on seeing a plant with a very bad appearance, thought that it was necessary to remedy it and removed one by one all the insects that he found. It seems that Linnaeus, when knowing what happened, suffered a “dreadful” migraine attack and decided never to think about the cochineal again.

From the Iberian peninsula to everywhere

Until the beginning of the 19th century, the Spanish government did not bother to cultivate the cochineal on the Iberian peninsula, because it dominated both its production at source and its international trade. Thus, it was in 1820 that the first successful cultivation of cochineal on the Iberian Peninsula was achieved. At a time when Spain saw its American colonies in danger (in 1825 only Cuba, Puerto Rico and Santo Domingo remained), this was a desperate attempt to maintain the great treasure of the American colonies, which had contributed so much money to the Spanish empire.

Prickly pears had already been introduced to the Iberian Peninsula in the 16th century, mainly because they were an easily preserved nutritious food, perfect for the long boat journeys between the colonies and Spain. Prickly pears were cultivated in Andalusia, where they were highly valued for their fruit.

Apart from the fact that the environmental conditions on the peninsula were not very favourable for the development of the cochineal, when attempts were made in the 19th century to redirect the crops towards non-food production, only a few producers were willing to sacrifice the plants in favour of the parasite that killed them, so that cochineal cultivation was not as successful as expected.

From Andalusia, within a few years, prickly pear cacti and cochineal spread throughout the Mediterranean and far beyond. Around 1825, cochineal cultivation spread to the Canary Islands, where the climate was more favourable for its development, and where it still survives today and has a Protected Designation of Origin. In 1828, a shipment of about seventy infested plants and more than six hundred prickly pear healthy cuttings that a Dutch spy managed to steal from a plantation of carmine in Cadiz arrived in Java, marking the beginning of the cultivation of this insect on the Indonesian island. During the 1830s, the French also brought cochineal-infested cladodes from Spain to North Africa, and the Portuguese introduced it to Madeira.

Cochineal crop decline and prickly pear invasion

Mexico, Guatemala, Java and the Canary Islands were the main producers of cochineal in the first half of the 19th century. During the second half of the 19th century, the cochineal trade declined due to two key factors. On the one hand, industrial society demanded changes in fashion, changing red from a colour symbolising power and high social status to a vulgar colour associated with sin, particularly sexual sin. On the other hand, after the accidental discovery in 1856 of mauvein, the first chemical dye, the development of organic chemistry and the synthesis of hundreds of new colours, cheaper to produce and easier to apply in dyeing, began.

Thus, cochineal cultivation lost interest and the insect disappeared from the places where it did not find the optimal conditions to grow. The insect disappeared, but the prickly pears, whether or not they were valued for other uses, survived wherever they had arrived. And as they had no natural enemy, they spread easily everywhere.

Cochineal in Catalonia

Since 2007, the wild cochineal, Dactylopius opuntiae, has been known to be present on the Iberian Peninsula. Like Dactylopius coccus, this insect pest exclusively attacks Opuntia ficus-indica, but differs from the “cultivated” cochineal in that it does not produce as much carminic acid and is more aggressive towards its host. It is therefore used as a biological control agent for this invasive plant.

In the Iberian Peninsula, the wild cochineal is spreading naturally from the south to the north: in 2010 it was reported in the Valencian Community and in 2014 its presence was detected in the area around the Carretera de les Aigües (Barcelona); in 2016, some inoculation tests were carried out in the Medes Islands (L’Estartit, Girona) to promote the control of invasive prickly pears; and in 2020 it was detected in the municipality of Roses.

What do we do at LIFE medCLIFFS?

Although cochineal is currently found in the Cap de Creus area on a regular basis, there are some populations of prickly pear cactus on the cliffs that are protected from attack by Dactylopius opuntiae. It is just in these isolated areas where the LIFE medCLIFFS has started to carry out demonstrative work on the biological control of prickly pear cactus.

The control work consisted of inoculating healthy prickly pears with cladodes infested with Dactylopius opuntiae, collected on the same day to ensure the survival of the maximum number of insects. Once the plants have been inoculated, the evolution of the pest will be monitored and its effectiveness as a biological control agent will be determined.

 

Text: Roser Melero (@la.macarulla)