This archive report was first published on 5 June 2020.
Laikipia County in Kenya is facing a severe threat from an invasive cactus plant, known as the prickly pear, which has been spreading rapidly across the region.
The cactus plant, scientifically known as Dactylopius opuntiae 'stricta', was introduced to the area by British colonial officials in the late 1940s and early 1950s.
Native to the Americas, the prickly pear has proven to be a major challenge for cattle keepers in the region, as it invades large areas of grasslands, forms dense stands, and prevents access to water resources and pasture.
According to a group of scientists from the Centre for Agriculture and Bioscience International (Cabi), the cochineal insect, a tiny insect that is used to make food colours, has been found to be effective in controlling the spread of the prickly pear.
‘Dactylopius opuntiae 'stricta' biotype cochineal is more effective as a sustainable bio-control in the fight against the invasive common pest pear Opuntia stricta in Laikipia County, Kenya, compared to physical and/or chemical control,’ the scientists said.
The cochineal insect, which is soft-bodied, flat, and oval-shaped, attaches itself to the cactus pads in colonies, penetrates the cacti plant, and feeds on its juices.
Activities to control the invasion in Laikipia were initiated in 2010, and the cochineal insects were mass-reared and released at several localities on Ol Jogi Wildlife Conservancy in Laikipia in 2014.
According to a preliminary survey, the cochineal insect had contributed to a significant reduction in the number of shoots, flowers, and fruits of plants with cochineal.
‘Fruits that were produced on plants with the cochineal were also smaller and had fewer seeds,’ the scientists reported.
‘Many of the plants with cochineal had collapsed. The number of cladodes was reduced by approximately 80 per cent within a few years after release of the cochineal... Opuntia fruit production was also significantly reduced with 79 and 81 per cent of O. stricta plants in the site, with cochineal having no immature or mature fruits,’ they added.
