A preliminary analysis of the costs and benefits of the biological control agent Dactylopius opuntiae on Opuntia stricta in Laikipia County, Kenya

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.