Agent-based modeling for insect resistance management
2023
Alcantara, E. | Jacildo, A.
For more than twenty years, growing of Bt corn has brought significant economic benefits to Philippine farmers through implementation of an effective insect resistance management program (IRM). The IRM is intended to reduce selection pressure in order to delay the rapid evolution of Asian corn borer (ACB) Ostrinia furnacalis resistance to insecticidal Bt corn. The core element of the program is the high dose plus refuge strategy. Using agent-based modeling (AB-M) with the NetLogo algorithm, authors investigated the outcome of different genetically modified Bacillus thuringiensis (Bt) corn growing scenarios wherein the HD/R strategy is compromised. AB-M is a computer simulation method where a system is analyzed by its individual agents that interact with each other. The foundation of AB-M is its ability to understand macro-phenomena emerging from microscale behavior. In this simulation study, a Bt corn field is modeled as a 2D grid of non-moving agents designated as patches. The ACB is modeled as mobile agents. Genotypes for ACB susceptibility or resistance to Bt corn were assigned for both single and pyramid Bt corn events. A scenario of Bt corn patches containing different types of non-Bt corn refuges was also incorporated in the model. The model was iterated for five generations. The simulation revealed that in the absence of refuge, resistant individuals quickly dominated the ACB population in the Bt corn patch. When the proportion of resistant individuals in a single event Bt corn patch approached the threshold of 5%, increasing the size of any of the refuge types from 15% to 30% did not stop the further increase in the proportion of resistant individuals in the Bt corn patch. Similarly, at the threshold of 5% with 15% refuge, pyramid Bt corn with strip refuge offered superior performance in preventing rapid evolution of ACB resistance.
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