Understanding population dynamics and management strategies for a newly emerging pest Carea sp. in Eucalyptus plantations in Indonesia through a mathematical model

In this current study, we investigate the population dynamics of Carea sp. (Lepidoptera: Nolidae), a newly emerging pest in Indonesian Eucalyptus plantations, utilizing the MELP-SI-B mathematical model based on the first reported outbreak in 2022. The larval infestation of Carea sp. has been observed to stunt plant growth and can even lead to plant mortality. The proposed model incorporates pest management interventions, including chemical control with pesticides and biological control through the introduction of natural predators. Analysis of the deterministic compartment model revealed four locally asymptotically stable equilibrium points, validated using eigenvalue approach and application of the center manifold theorem. Bifurcation diagrams are presented to elucidate the relationships between all equilibrium points. An optimal control problem is explored within this model, considering three scenarios: chemical control without predators, simultaneous chemical control with predators, and chemical control followed by predator management. The results of the optimal control strategy analysis highlight the critical importance of timing the initial chemical control application for effective pest management. Notably, this study reveals that a combined approach involving chemical control (without predators) followed by predator management during the post-chemical control period yields the most favorable outcomes among the examined strategies.