"Optimal removal of host plants to slow the spread of invasive insects"Lampert, AdamInvasive species are spreading worldwide, causing damage to ecosystems, biodiversity, agriculture, and human health. Efforts to prevent the establishment of invasive species in new regions sometimes fail, which necessitates the containment of established invaders to prevent or slow their further spread. A major question is, therefore, how to cost-effectively allocate treatment efforts over space and time to contain the species’ population. In this study, we examine what is the most cost-effective strategy to slow the spread of the spongy moth (Lymantria dispar) in North America. We developed a spatially-explicit mathematical model of the moth’s population dynamics, and we examined how to cost-effectively combine three treatment methods: (1) removal of host plants on which the moth depends for nutrition, (2) mating disruption in which false pheromone flakes are distributed to destruct the males, and (3) insecticide application. Each method affects the moth population differently and can be applied in different locations across the landscape. We developed a novel computer algorithm that could find the optimal strategy that minimizes the overall cost. Our results show that, to stop the spread of the moth, it is more cost-effective to remove many host plants in a relatively narrow area rather than removing just a few host plants over a wide area. Furthermore, employing mating disruption is also necessary and should be done in the area between (1) the area where the host plants are removed and (2) the area that is kept free from the moth’s presence. The cost difference between the optimal strategy and less effective strategies could amount to tens of hundreds of percentages of the total cost, highlighting the importance of strategic planning in ensuring the success of containment efforts. |
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