Abstract
Opuntia stricta (Haw.) Haw (Cactaceae) is invasive in Laikipia County, Kenya, impacting negatively on biodiversity and livelihoods. To control this invasive plant the biocontrol agent Dactylopius opuntiae (Cockerell) (Hemiptera; Dactylopiidae) ‘stricta’ biotype was released in 2014. A preliminary once-off survey to determine the impact of the cochineal revealed that it had contributed to a significant reduction in the number of cladodes, flowers and fruit of plants with cochineal. Fruits that were produced on plants with the cochineal were also smaller and had fewer seeds. Although still preliminary, an analysis of the costs of implementing this biocontrol programme indicates that it is the most cost-effective management intervention compared to physical and/or chemical control. Although the impact of the cochineal is still fairly localized we are confident that it will establish in much of the invaded range and reduce the impacts of the invasive cactus, consequently improving rangeland condition and livelihoods.
Highlights
A large number of cactus species have been introduced to countries around the world as ornamentals (250) or for food and fodder production (45) (Novoa et al 2015)
We do assume that the cochineal will establish widely, and impact significantly, on O. stricta throughout the invaded range in Laikipia. This rapid preliminary and limited assessment has demonstrated that D. opuntiae ‘stricta’ biotype is having a significant impact on O. stricta populations in Laikipia, Kenya, resulting in a significant reduction in the number of cladodes, flowers and fruit
The number of cladodes was reduced by approximately 80% within a few years after release of the cochineal, if one assumes that the impact of the cochineal within the quadrat was similar to that outside of it
Summary
A large number of cactus species have been introduced to countries around the world as ornamentals (250) or for food and fodder production (45) (Novoa et al 2015). About 20% (57) of those species that have been introduced outside of their native range have become invasive, impacting negatively on biodiversity, livestock production, and rural communities dependent on these resources (Ueckert et al 1990; Beinart 2003; Larsson 2004; Novoa et al 2017, 2019; Shackleton et al 2017). South Africa has the highest number of invasive cactus species (35), followed by Australia (26), and Spain (24) (Novoa et al 2015). Having been recorded as invasive in Kenya, while other species such as O. microdasys (Lehm.) Pfeiff., Penioecereus serpentinus Knuth are present but have not yet escaped cultivation as in other parts of the world (Witt and Luke 2017; Witt et al 2018)
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