Damping-off
Causal Agent
Damping-off is caused by Pythium, Fusarium and Phytophthora species, Rhizoctonia solani.
Symptoms
If seedlings are killed before they emerge, bare spots are left in rows. This symptom can be mistaken for a poor germination rate of seed. After seedlings emerge, the stems turn brown at the base and the seedlings fall over and die. The roots of these seedlings rot.
Disease Cycle
Damping-off pathogens are soilborne and are ubiquitous even in small amounts of soil and dirt. They can be found in dirt adhering to reused seed trays and benches. After planting, spores or mycelium colonize the soil in the trays, and subsequently, the seedlings. Chance of seeing damping-off increases when seedlings are kept very wet. For example, a field’s gradient can lead to water pooling at one end. Some damping-off pathogens like Pythium have motile spores that can swim in a film of water.
Management
The most important management option to prevent damping-off in peas or beans is seed treatment with a fungicide. Cleaning tools and equipment that come in contact with soil minimizes damping-off pathogens moving from one field to the next. If damping-off has occured in the past, using smooth-seeded peas instead of wrinkle-seed pea varieties can reduce disease incidence. Cultural practices to reduce incidence include shallow planting in well-drained soils, reducing compaction, and minimizing irrigation (shortly after planting).