Damping-off of Seedlings
F. L. Pfleger and S. L. Gould
Damping-off generally refers to sudden plant death in the seedling stage due to the attack of fungi (see figure 1). These fungi are soilborne and are stimulated to grow and infect the seed or seedling by nutrients released from a germinating seed. However, seedlings may be injured or killed by something other than fungi, for example, toxic materials in the soil, excess or deficient soil moisture, seed defects, temperature extremes, toxic gases in the air, etc. A correct diagnosis is the key to effective control measures.
Figure 1. A seedling infected with damping-off fungi. Note the stem constriction near the soil line, a symptom characteristically associated with damping-off. This phase of the disease is called postemergence damping-off.
Figure 2. Seedlings grown in a container of soil infested with damping-off fungi.
Occurrence and Importance
Damping-off disease of seedlings is widely distributed and is a problem on a worldwide basis. It occurs in most soils, temperate and tropical climates, and in greenhouses. The disease affects seeds and seedlings of various crops. The amount of damage the disease causes to seedlings depends on the fungus, soil moisture, and temperature. Normally, however, cool wet soils favor development of the disease. Seedlings in seedbeds often are completely destroyed by damping-off, or they die after transplanting. Frequently, germinating seeds are killed by damping-off fungi before they emerge from the ground, which accounts for poor stands in many crops. Older plants are seldom killed by damping-off fungi mainly because the development of secondary stem tissue forms a protective barrier and limits fungal penetration. However, portions of the roots and stems still can be attacked, resulting in poor growth and reduced yields.
Information Source: Minnesota Extension Service
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