Neuenschwander, P. | bioRxiv Science

bioRxiv2025

Ex ante analyses can predict natural enemy efficacy in biological control

The success rate of biological control programs against invasive species is low because the efficacy of released natural enemies is unknown. Deconstruction of the successful biological control of the highly destructive cassava mealybug (CM) and cassava green mite (CGM) in Africa is used to show how ex ante pre-release analyses of natural enemies can increase the success rate. A meta-population tri-trophic physiologically based demographic model (PBDM) of the cassava system accurately predicted the weather-driven daily dynamics of cassava, CM, CGM, and their introduced natural enemies across the ecological zones of Africa. Marginal analyses of the simulation data enabled parsing the differing contributions of two exotic parasitoids and a fungal pathogen in the control of CM, and the contributions of two mite predators, local pathogens and rainfall mortality in the control of CGM. The contribution of each natural enemy to the [~]95% recovery of cassava yields is estimated. The results show ex ante analyses of prospective natural enemies using well parameterized PBDMs can predict natural enemy prerelease efficacy across vast geographic areas and increase the success rate of biological control programs. Ex ante analyses can also explain whether biological control is a viable option (e.g., Cure et al. 2020).

ecology↗

bioRxiv2019

Human Demographic Outcomes of a Restored Agro-Ecological Balance

As prominent features of the Anthropocene, biodiversity loss and invasive species are exacting serious negative economic, environmental and societal impacts. While the monetary aspects of species invasion are reasonably well assessed, their human and social livelihood outcomes often remain obscure. Here, we empirically demonstrate the (long-term) human demographic consequences of the 1970s invasion of a debilitating pest affecting cassava -a carbohydrate-rich food staple-across sub-Saharan Africa. Successive pest attack in 18 African nations inflicted an 18 {+/-} 29% drop in crop yield, with cascading effects on birth rate (-6%), adult mortality (+4%) and decelerating population growth. The 1981 deliberate release of the parasitic wasp Anagyrus lopezi permanently restored food security and enabled parallel recovery of multiple demographic indices. This analysis draws attention to the societal repercussions of ecological disruptions in subsistence farming systems, providing lessons for efforts to meet rising human dietary needs while safeguarding agro-ecological functionality and resilience during times of global environmental change.

ecology↗