Root Rot or Damping Off

Root Rot or Damping Off

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Scientific Name
genus: Pythium
Pest Alias
Damping-Off, Pythium Root Rot, Pythium Soil Fungus, Seedling Root Rot, Soil Fungi
Kingdom:
Chromista
Phylum:
Oomycota
Class:
Peronosporomycetes
Order:
Peronosporales
Family:
Pythiaceae
Genus:
Pythium

Root Rot or Damping Off

(Common Names: Damping-off; Pythium root rot; Seedling root rot; Soil fungi)

Causal AgentPythium spp. (e.g. Pythium ultimum, P. aphanidermatum, P. irregulare)
Pathogen TypeOomycete (water mould – not a true fungus)
Primary HostsA wide range of vegetables, ornamentals, turf, and seedlings
Common NamesDamping-off, seed rot, root rot, water mould wilt

Symptoms

  • Pre-emergence damping-off: seeds rot before germinating

  • Post-emergence damping-off: seedlings collapse at the soil line due to stem constriction and rot

  • Root rot: discoloured, water-soaked roots that easily slough off; leads to stunted, wilted plants

  • Wilt symptoms: plants wilt during the day but may recover temporarily at night before eventual death

️ Favourable Conditions

  • Overwatering, poor drainage

  • High humidity, cloudy conditions, or crowded plantings

  • Cool to warm soils (15–25°C), particularly in greenhouse or nursery environments

✅ Management Strategies

StrategyRecommendation
SanitationUse clean trays, tools, and growing media; avoid contaminated water
EnvironmentalImprove airflow and drainage; avoid overwatering or wet foliage
Cultural ControlAvoid overcrowding seedlings; use bottom watering when possible
Chemical ControlApply registered fungicides (e.g. metalaxyl-M, mefenoxam, etridiazole)
Biological ControlIncorporate Trichoderma spp., Streptomyces, or other biocontrols
Seed TreatmentUse treated seed or apply protective seed drenches with appropriate fungicides

Summary for Growers

Pythium damping-off and root rot are seedling-killing diseases favoured by wet, cool conditions. Prevention is the best defence—ensure good hygiene, drainage, and consider seedling fungicide drenches or biologicals in sensitive crops and settings.

 

Pythium is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but Pythium insidiosum is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequently a vector for their transmission.[1]

Morphology

Hyphae
Pythium species, like others in the family Pythiaceae, are usually characterized by their production of coenocytic hyphae without septations.
Oogonia
Generally contain a single oospore.
Antheridia
Contain an elongated and club-shaped antheridium.

Ecological importance

Pythium

Pythium-induced root rot is a common crop disease. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses.[2] Thus there is tremendous interest in genetic host resistance, but no crop has ever developed adequate resistance to Pythium.[3] This disease complex usually involves other pathogens such as Phytophthora and Rhizoctonia. Pythium wilt is caused by zoospore infection of older plants, leading to biotrophic infections that become necrotrophic in response to colonization/reinfection pressures or environmental stress,[2][4][5] leading to minor or severe wilting caused by impeded root functioning.[2][6]

Many Pythium species, along with their close relatives Phytophthora, are plant pathogens of economic importance in agriculture. Pythium spp. tend to be very generalistic and unspecific in their large range of hosts,[7] while Phytophthora spp. are generally more host-specific.

For this reason, Pythium spp. are more devastating in the root rot they cause in crops, because crop rotation alone often does not eradicate the pathogen as Pythium spp. are also good saprotrophs, and survive for a long time on decaying plant matter.

In field crops, damage by Pythium spp. is often limited to the area affected, as the motile zoospores require ample surface water to travel long distances. Additionally, the capillaries formed by soil particles act as a natural filter and effectively trap many zoospores. However, in hydroponic systems inside greenhouses, where extensive monocultures of plants are maintained in plant nutrient solution (containing nitrogen, potassium, phosphate, and micronutrients) that is continuously recirculated to the crop, Pythium spp. cause extensive and devastating root rot and is often difficult to prevent or control.[2][6][7][8] The root rot affects entire operations (tens of thousands of plants, in many instances) within two to four days due to the inherent nature of hydroponic systems where roots are nakedly exposed to the water medium, in which the zoospores can move freely.[6][7][8] Various Pythium populations have been known to have resistance to mefenoxam since the 1980s[9] and metalaxyl since 1984.[10]

Several Pythium species, including P. oligandrum, P. nunn, P. periplocum, and P. acanthicum, are mycoparasites of plant pathogenic fungi and oomycetes, and have received interest as potential biocontrol agents.

Species

Globisporangium sylvaticum was formerly placed here as Pythium sylvaticum

See also

References

  1. ^ "Ecogrow Fungus Gnat". 17 March 2014.
  2. ^ a b c d Jarvis, W. R. (1992). Managing diseases in greenhouse crops. Saint Paul, Minnesota: APS Press. ISBN 978-0-89054-122-7.[page needed]
  3. ^ Sutton, John Clifford; Sopher, Coralie Rachelle; Owen-Going, Tony Nathaniel; Liu, Weizhong; Grodzinski, Bernard; Hall, John Christopher; Benchimol, Ruth Linda (1990-01-06). "Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives". Summa Phytopathologica. 32 (4): 307–321. doi:10.1590/S0100-54052006000400001. ISSN 0100-5405.
  4. ^ Owen-Going, Tony Nathaniel (2005). Quantitative investigations of phenolic compounds associated with root rot of hydroponic pepper, Capsicum annuum L., caused by Pythium aphanidermatum (Edson) Fitzp (PhD thesis). University of Guelph. ISBN 978-0-494-17779-2. OCLC 271429383.[page needed]
  5. ^ T. N. Owen-Going; C. W. Beninger; J. C. Sutton & J. C. Hall (2008). "Accumulation of phenolic compounds in plants and nutrient solution of hydroponic peppers inoculated with Pythium aphanidermatum". Canadian Journal of Plant Pathology. 30 (2): 214–225. doi:10.1080/07060661.2008.10540537. S2CID 86573443.
  6. ^ a b c Bagnall, Roger (2007). Control of Pythium wilt and root rot of hydroponically grown lettuce by means of chemical treatment of the nutrient solution (MSc thesis). University of Pretoria. OCLC 216915405.[page needed]
  7. ^ a b c Owen-Going, Tony Nathaniel (2002). Etiology and epidemiology of Pythium root rot in bell pepper (Capsicum annuum L.) in commercial-scale and small-scale hydroponic systems (MSc thesis). University of Guelph. ISBN 978-0-612-71820-3. OCLC 55510696.
  8. ^ a b T. N. Owen-Going, J. C. Sutton & B. Grodzinski (2003). "Relationships of Pythium isolates and sweet pepper plants in single-plant hydroponic units". Canadian Journal of Plant Pathology. 25 (2): 155–167. Bibcode:2003CaJPP..25..155O. doi:10.1080/07060660309507064. S2CID 85004809.
  9. ^ Del Castillo Múnera, Johanna; Hausbeck, Mary K. (2016). "Characterization of Pythium Species Associated With Greenhouse Floriculture Crops in Michigan". Plant Disease. 100 (3). American Phytopathological Society: 569–576. Bibcode:2016PlDis.100..569D. doi:10.1094/pdis-03-15-0296-re. ISSN 0191-2917. PMID 30688597.
  10. ^ Sanders, P. L. (1984). "Failure of Metalaxyl to Control Pythium Blight on Turfgrass in Pennsylvania". Plant Disease. 68 (1). American Phytopathological Society: 776. Bibcode:1984PlDis..68Q.776S. doi:10.1094/pd-68-776. ISSN 0191-2917.

Further reading

Wikimedia Commons has media related to Pythium.
 
Pythium
 
Authority control databases: National Edit this at Wikidata

This article uses material from the Wikipedia article "Pythium", which is released under the Creative Commons Attribution-Share-Alike License 3.0. Content may have been omitted from the original, but no content has been changed or extended.

Root Rot or Damping Off

genus: Pythium
Scientific Name
genus: Pythium
Pest Alias
Damping-Off, Pythium Root Rot, Pythium Soil Fungus, Seedling Root Rot, Soil Fungi
Kingdom:
Chromista
Phylum:
Oomycota
Class:
Peronosporomycetes
Order:
Peronosporales
Family:
Pythiaceae
Genus:
Pythium
Root Rot or Damping Off

Root Rot or Damping Off

(Common Names: Damping-off; Pythium root rot; Seedling root rot; Soil fungi)

Causal AgentPythium spp. (e.g. Pythium ultimum, P. aphanidermatum, P. irregulare)
Pathogen TypeOomycete (water mould – not a true fungus)
Primary HostsA wide range of vegetables, ornamentals, turf, and seedlings
Common NamesDamping-off, seed rot, root rot, water mould wilt

Symptoms

  • Pre-emergence damping-off: seeds rot before germinating

  • Post-emergence damping-off: seedlings collapse at the soil line due to stem constriction and rot

  • Root rot: discoloured, water-soaked roots that easily slough off; leads to stunted, wilted plants

  • Wilt symptoms: plants wilt during the day but may recover temporarily at night before eventual death

️ Favourable Conditions

  • Overwatering, poor drainage

  • High humidity, cloudy conditions, or crowded plantings

  • Cool to warm soils (15–25°C), particularly in greenhouse or nursery environments

✅ Management Strategies

StrategyRecommendation
SanitationUse clean trays, tools, and growing media; avoid contaminated water
EnvironmentalImprove airflow and drainage; avoid overwatering or wet foliage
Cultural ControlAvoid overcrowding seedlings; use bottom watering when possible
Chemical ControlApply registered fungicides (e.g. metalaxyl-M, mefenoxam, etridiazole)
Biological ControlIncorporate Trichoderma spp., Streptomyces, or other biocontrols
Seed TreatmentUse treated seed or apply protective seed drenches with appropriate fungicides

Summary for Growers

Pythium damping-off and root rot are seedling-killing diseases favoured by wet, cool conditions. Prevention is the best defence—ensure good hygiene, drainage, and consider seedling fungicide drenches or biologicals in sensitive crops and settings.

 

Pythium is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but Pythium insidiosum is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequently a vector for their transmission.[1]

Morphology

Hyphae
Pythium species, like others in the family Pythiaceae, are usually characterized by their production of coenocytic hyphae without septations.
Oogonia
Generally contain a single oospore.
Antheridia
Contain an elongated and club-shaped antheridium.

Ecological importance

Pythium

Pythium-induced root rot is a common crop disease. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses.[2] Thus there is tremendous interest in genetic host resistance, but no crop has ever developed adequate resistance to Pythium.[3] This disease complex usually involves other pathogens such as Phytophthora and Rhizoctonia. Pythium wilt is caused by zoospore infection of older plants, leading to biotrophic infections that become necrotrophic in response to colonization/reinfection pressures or environmental stress,[2][4][5] leading to minor or severe wilting caused by impeded root functioning.[2][6]

Many Pythium species, along with their close relatives Phytophthora, are plant pathogens of economic importance in agriculture. Pythium spp. tend to be very generalistic and unspecific in their large range of hosts,[7] while Phytophthora spp. are generally more host-specific.

For this reason, Pythium spp. are more devastating in the root rot they cause in crops, because crop rotation alone often does not eradicate the pathogen as Pythium spp. are also good saprotrophs, and survive for a long time on decaying plant matter.

In field crops, damage by Pythium spp. is often limited to the area affected, as the motile zoospores require ample surface water to travel long distances. Additionally, the capillaries formed by soil particles act as a natural filter and effectively trap many zoospores. However, in hydroponic systems inside greenhouses, where extensive monocultures of plants are maintained in plant nutrient solution (containing nitrogen, potassium, phosphate, and micronutrients) that is continuously recirculated to the crop, Pythium spp. cause extensive and devastating root rot and is often difficult to prevent or control.[2][6][7][8] The root rot affects entire operations (tens of thousands of plants, in many instances) within two to four days due to the inherent nature of hydroponic systems where roots are nakedly exposed to the water medium, in which the zoospores can move freely.[6][7][8] Various Pythium populations have been known to have resistance to mefenoxam since the 1980s[9] and metalaxyl since 1984.[10]

Several Pythium species, including P. oligandrum, P. nunn, P. periplocum, and P. acanthicum, are mycoparasites of plant pathogenic fungi and oomycetes, and have received interest as potential biocontrol agents.

Species

Globisporangium sylvaticum was formerly placed here as Pythium sylvaticum

See also

References

  1. ^ "Ecogrow Fungus Gnat". 17 March 2014.
  2. ^ a b c d Jarvis, W. R. (1992). Managing diseases in greenhouse crops. Saint Paul, Minnesota: APS Press. ISBN 978-0-89054-122-7.[page needed]
  3. ^ Sutton, John Clifford; Sopher, Coralie Rachelle; Owen-Going, Tony Nathaniel; Liu, Weizhong; Grodzinski, Bernard; Hall, John Christopher; Benchimol, Ruth Linda (1990-01-06). "Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives". Summa Phytopathologica. 32 (4): 307–321. doi:10.1590/S0100-54052006000400001. ISSN 0100-5405.
  4. ^ Owen-Going, Tony Nathaniel (2005). Quantitative investigations of phenolic compounds associated with root rot of hydroponic pepper, Capsicum annuum L., caused by Pythium aphanidermatum (Edson) Fitzp (PhD thesis). University of Guelph. ISBN 978-0-494-17779-2. OCLC 271429383.[page needed]
  5. ^ T. N. Owen-Going; C. W. Beninger; J. C. Sutton & J. C. Hall (2008). "Accumulation of phenolic compounds in plants and nutrient solution of hydroponic peppers inoculated with Pythium aphanidermatum". Canadian Journal of Plant Pathology. 30 (2): 214–225. doi:10.1080/07060661.2008.10540537. S2CID 86573443.
  6. ^ a b c Bagnall, Roger (2007). Control of Pythium wilt and root rot of hydroponically grown lettuce by means of chemical treatment of the nutrient solution (MSc thesis). University of Pretoria. OCLC 216915405.[page needed]
  7. ^ a b c Owen-Going, Tony Nathaniel (2002). Etiology and epidemiology of Pythium root rot in bell pepper (Capsicum annuum L.) in commercial-scale and small-scale hydroponic systems (MSc thesis). University of Guelph. ISBN 978-0-612-71820-3. OCLC 55510696.
  8. ^ a b T. N. Owen-Going, J. C. Sutton & B. Grodzinski (2003). "Relationships of Pythium isolates and sweet pepper plants in single-plant hydroponic units". Canadian Journal of Plant Pathology. 25 (2): 155–167. Bibcode:2003CaJPP..25..155O. doi:10.1080/07060660309507064. S2CID 85004809.
  9. ^ Del Castillo Múnera, Johanna; Hausbeck, Mary K. (2016). "Characterization of Pythium Species Associated With Greenhouse Floriculture Crops in Michigan". Plant Disease. 100 (3). American Phytopathological Society: 569–576. Bibcode:2016PlDis.100..569D. doi:10.1094/pdis-03-15-0296-re. ISSN 0191-2917. PMID 30688597.
  10. ^ Sanders, P. L. (1984). "Failure of Metalaxyl to Control Pythium Blight on Turfgrass in Pennsylvania". Plant Disease. 68 (1). American Phytopathological Society: 776. Bibcode:1984PlDis..68Q.776S. doi:10.1094/pd-68-776. ISSN 0191-2917.

Further reading

Wikimedia Commons has media related to Pythium.
 
Pythium
 
Authority control databases: National Edit this at Wikidata

This article uses material from the Wikipedia article "Pythium", which is released under the Creative Commons Attribution-Share-Alike License 3.0. Content may have been omitted from the original, but no content has been changed or extended.