Tobacco

Yellow Stunt

Fusarium/Pythium/Rhizoctonia complex

Fungus

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In a Nutshell

  • Yellowing of leaves.
  • Wilting of aerial parts.
  • Occurrence of darkened roots.
  • Necrosis of stem tissue directly above the soil line.
  • Plant death.
  • Necrotic lesions with concentric ring pattern on leaves.

Can also be found in

1 Crops
Tobacco

Tobacco

Symptoms

The initial symptom of the disease appears when the aerial part of the plant begins to wilt, followed by a yellowing process and tissue necrosis, causing the plant to die. Yellow stunt or “yellow disease complex” seems to be triggered by excessive moisture levels at the root zone, resulting in a lack of aeration for the roots. Within this context, the collapse of the tobacco roots favours the penetration or alters the plant susceptibility towards the invasion of pathogens associated with the yellow stunt.

Recommendations

Organic Control

Use plant varieties that are resistant to soil pathogens.

Chemical Control

The yellow stunt cannot be chemically controlled and occurs due to poor water management and soil saturation.

What caused it?

Tobacco has a low tolerance to O2 deficit and the excess of CO2. And the combination of excessive moisture, lack of oxygen and high temperatures could cause the root system to collapse. The collapse of tobacco roots favours the penetration of pathogens such as Fusarium spp., Rhizoctonia solani, Pythium spp. etc. associated with a yellow stunt. The consequences depend on various factors, such as the growth stage, environmental conditions, duration and the percentage of affected roots.

Preventive Measures

  • In the nursery, use optimum seed rate to avoid over-crowding.
  • Avoid high-density planting of crops during transplant.
  • Practice irrigation by reducing the application of excessive amounts that result in saturated soil.
  • To eliminate the compacted layers, practice the sub-soiling method.
  • Implement high ridge systems by planting on the top of ridges.
  • Seeding of green cover crops can improve soil structure.
  • Utilize varieties with higher tolerance to prevent soil born pathogens.

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