Opuntia stricta poses a significant threat to livelihoods in parts of Africa, and the costs of physical and chemical control are beyond the affordability of most communities affected. To provide cost-effective control, the biological control agent Dactylopius opuntiae was introduced to Laikipia County, Kenya, in 2014. To determine perceptions of its efficacy a semi-structured questionnaire survey was undertaken among community members living in and around the village of Il Polei, Laikipia. Perceptions of O. stricta in this area were assessed in a previous study prior to the release of the agent, providing an opportunity to determine changes in observations following its introduction. Most respondents (percentages in brackets) believed that the density (80%) and size (85%) of O. stricta plants had decreased in the last five years, together with a reduction in flower and fruit production (97%). The impact of the agent on O. stricta resulted in an improvement in livestock health, with 86% of respondents now considering biological control to be safe compared to 36% in a previous study. More residents are involved in the control of O. stricta (78 compared to 20% in the previous study), probably because they have seen how effective biological control is, a key motivational factor. The effectiveness of D. opuntiae appears to have encouraged residents to increase their efforts to control O. stricta probably because plants are now smaller and less dense, and as such easier to remove using other means. The long-term benefits of a reduction in the distribution and abundance of O. stricta will probably best be determined after additional time has passed to allow for a further decrease in O. stricta and an increase in natural vegetation cover.
Witt et al. (Wed,) studied this question.