Percolation-based risk index for pathogen invasion: application to soilborne disease in propagation systems

Area of Science:

• Agricultural Science
• Plant Pathology
• Epidemiology

Background:

• Fungal pathogens like Rhizoctonia solani threaten seedling propagation systems, especially in organic agriculture.
• Host density is a controllable agronomic factor, yet its link to disease invasion risk is poorly understood.

Purpose of the Study:

• To introduce and apply a percolation framework to analyze the relationship between host density and fungal disease invasion risk in agricultural propagation systems.
• To quantify the impact of planting density on the spread of Rhizoctonia solani.

Main Methods:

• An experiment was conducted using replicated propagation systems with varying planting densities to study R. solani spread.
• A percolation-based epidemiological model was fitted to experimental data using Bayesian inference to estimate pathogen transmission probability.
• Risk of invasion was calculated based on estimated transmission probabilities at different densities.

Main Results:

• A nonlinear relationship was identified between disease invasion and inter-plant spacing.
• Evidence for a spatial threshold for epidemic invasion was demonstrated, indicating critical planting densities for disease spread.
• Pathogen transmission probability and invasion risk varied significantly with planting density.

Conclusions:

• Planting density is a critical factor influencing fungal pathogen spread and disease invasion risk in seedling propagation.
• The developed percolation framework provides a novel method for evaluating disease control strategies based on spatial arrangement.
• Optimizing inter-plant spacing can be an effective strategy to manage fungal diseases in agricultural settings.