Spatio-temporal Development of Pea Root Rot Disease through Secondary Infections during a Crop Cycle

Spatio-temporal development of pea root rot was experimentally characterized. Experiments performed under controlled conditions with trap plants located at varying distances from a diseased source plant indicated that disease spread from a diseased plant to a healthy one was generally below 15 cm. A field experiment was conducted to measure disease spread gradients and the rate of secondary infection at two planting densities, 70 and 140 plants/m2. Relationships between plant and root disease incidences, and between root disease incidence and root disease severity indicated a strong disease intensification both within and between diseased plants. Measurement of disease gradients indicated that disease did not spread farther than 10 cm from the diseased source plant, i.e. one and two plants away along a row at low and high planting densities respectively. Disease did not spread to neighbouring rows, located 15 cm away. Rates of secondary infection over 14-day periods ranged between zero (no disease increase) and 0.35 plant/plant/day, and was in general larger in high-density plots than in low-density plots. Implications of the results for disease management are discussed.