Seedling Diseases

1. Rhizoctonia solani
2. Pythium
3. (Aphanomycetes)

Seedling Diseases

Symptoms

1. Pre-emergence damping off
2. Post-emergence damping off
3. Root rot
4. Above ground necrosis

Seedling Diseases

Common Features

1. Soil associated
2. Wide host ranges

Seedling Diseases

Rhizoctonia solani

Symptoms

1. Below ground (root rot, stem cankers)
2. Above ground (stem cankers, foliar blights)

Seedling Diseases

Rhizoctonia solani

Signs

1. Hyphae/Mycelium (No spores, septate)
2. No asexual spores
3. Sclerotia
4. Sexual stage not common (Thanatephorus cucumeris)

Seedling Diseases

Rhizoctonia solani

1. Basidiomycete
2. Wide host range

Seedling Diseases

Pythium spp.

1. Oomycete (Chromistic Algae)
2. Wide host range

Seedling Diseases

Pythium spp.

Symptoms

1. Below ground (root rot, stem cankers)
2. Above ground (stem cankers, foliar blights)

Seedling Diseases

Pythium spp.

Signs

1. Hyphae/Mycelium (coenocytic)
2. Zoospores/Sporangia
3. Sexual Stage Common:

          Oospores

          Oogonia

          Antheridia

Seedling Blights

Control

1. Genetic Resistance

Seedling Blights

Control

1. Biological Control (Antagonists)

Seedling Blights

Control

1. Chemical Control

• Sterilized soil (Autoclaving, methyl bromide?)
• Seed Treatments (Mercury)
• Sprays (Copper sulfate, metalaxyl for oomycetes, Others for Rhizoctonia (e.g. Thiram, Captan, PNCB)

Seedling Blights

Control

1. Cultural Control

• Hasten maturity (reduce nitrogen)
• Avoid overcrowding
• Crop rotation
• Avoid contamination (pots, tools, irrigation)