Sustainable vector/pest control using the permanent Sterile Insect Technique

TL;DR

This paper develops minimalistic mathematical models to analyze the effectiveness of sterile insect technique (SIT) for sustainable vector control, identifying thresholds for successful elimination and proposing strategies for long-term population management.

Contribution

The paper introduces simplified models for vector population dynamics and SIT interactions, revealing thresholds and bistability that inform sustainable control strategies.

Findings

Elimination occurs when the basic offspring number is ≤ 1.

A threshold number of sterile males can effectively control wild populations.

Bistability allows for strategies to maintain low pest levels over time.

Abstract

Vector/Pest control is essential to reduce the risk of vector-borne diseases or losses in crop fields. Among biological control tools, the sterile insect technique (SIT), is the most promising one. SIT control generally consists of massive releases of sterile insects in the targeted area in order to reach elimination or to lower the pest population under a certain threshold. The models presented here are minimalistic with respect to the number of parameters and variables. The first model deals with the dynamics of the vector population while the second model, the SIT model, tackles the interaction between treated males and wild female vectors. For the vector population model, the elimination equilibrium $\mathbb{0}$ is globally asymptotically stable when the basic offspring number, $\mathcal{R}$, is lower or equal to one, whereas $\mathbb{0}$ becomes unstable and one stable positive equilibrium exists, with well-determined basins of attraction, when $\mathcal{R}>1$. For the SIT model, we obtain a threshold number of treated male vectors above which the control of wild female vectors is effective: the massive release control. When the amount of treated male vectors is lower than the aforementioned threshold number, the SIT model experiences a bistable situation involving the elimination equilibrium and a positive equilibrium. However, practically, massive releases of sterile males are only possible for a short period of time. That is why, using the bistability property, we develop a new strategy to maintain the wild population under a certain threshold, for a permanent and sustainable low level of SIT control. We illustrate our theoretical results with numerical simulations, in the case of SIT mosquito control.