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Thursday, March 11, 2021

Apple -- Crown and Collar Rot

From http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=40

Vegetables like beans can have crown rot (collar rot) when planted in cold soils. Different varieties of beans will show different tolerances to cold soils and collar rot development.

 

Cause: Phytophthora cactorum and other species, a soilborne fungus-like microorganism. Crown rot is a disease of the rootstock portion of the tree; collar rot is a disease of the scion portion. Both are serious diseases of apple and other orchard trees in British Columbia, Washington, and Idaho, and have become a problem in Oregon orchards with clonal rootstocks, principally Malling Merton 106. Crabapple can also be infected.

The fungus survives primarily as oospores in soil, organic debris, or infected tissues. Oospores produce a swimming spore stage (zoospores) when soils are at or near saturation. Zoospores swim to and infect roots. Movement within roots to the root crown is greatest between pink bud and shoot elongation.

Apple crown rot in Lebanon

 

Symptoms: In early fall, an affected tree shows bronzing, purpling, or yellowing foliage of one or more limbs, accompanied by bark reddening. There is a reduction in the size of leaves and terminal growth. Examination at the root crown or collar after scraping away the soil reveals dead bark. The cambium will be orange-brown to red-brown, eventually becoming dark brown instead of white. A distinct margin may separate healthy from infected tissues. In many cases, the tree may be completely girdled before its condition is noticed. Fire blight symptoms may be similar when confined to the rootstock.

'Antonovka', 'McIntosh', and 'Wealthy' apple seedlings and M9 clonal rootstocks have shown high resistance to collar rot. Moderately resistant: MM111, M2, M7, M26, 'Golden Delicious', 'Delicious', and 'Rome Beauty'. Susceptible: MM104 and MM106.A

 


Cultural control:

  1. Plant on a raised bed to help keep water away from trunks.
  2. Avoid overirrigation.
  3. During summer, examine root crowns of trees for collar rot and scrape off diseased tissues. Leave root crowns exposed to the air until late fall.
  4. Avoid wounding root crowns. If a wound is made, keep it uncovered and open to the air for the remainder of the season.

Chemical control: Apply before symptoms appear, especially in orchards favorable for disease development. No chemical will revitalize trees showing moderate to severe crown rot symptoms. Although resistance has not been reported, alternate materials so resistant fungi do not develop quickly.

  1. Agri-Fos at 1.25 to 2.5 qt/A. Do not combine with a copper-spray program for control of other diseases. 4-hour reentry.
  2. Aliette WDG at 2.5 to 5 lb/A. Spray foliage to run off. Follow manufacturer's directions for timing of spray. Do not apply within 14 days of harvest or more than 20 lb/A per season. Do not combine with a copper spray program for control of other diseases. Phytotoxicity may result if applied within 1 week of a copper spray. 12-hr reentry.
  3. Fixed copper products. Use 4 gal solution as a drench on the lower trunk of each tree in early spring or after harvest. Do not use if soil pH is below 5.5. Not considered organic since application is to the soil.
    1. Champ Formula 2 at 2.75 pints/100 gal water. 24-hr reentry.
    2. Copper-Count-N at 4 qt/100 gal water. 12-hr reentry.
    3. Cuprofix Disperss at 5 lb/100 gal water. 24-hr reentry.
    4. Kocide DF at 4 lb/100 gal water. 48-hr reentry.
    5. Nordox 75 WG at 2.5 lb/100 gal water. 24-hr reentry.
  4. Fosphite at 1 to 3 quarts/A. Do not use copper products within 20 days of treatment and do not use spray adjuvants. May also be injected into trunk. 4-hr reentry.
  5. Phostrol at 2.5 to 5 pt/A. 4-hr reentry.
  6. Ridomil Gold SL at 0.5 pint/100 gal water. Apply diluted mixture (based on trunk size measured at 12 inches above the soil line) around each tree trunk. Apply once at planting or in spring before growth starts. Apply again in fall after harvest. 48-hr reentry.

References:
Jones, A.L. and H.S. Aldwinkle. 1990. Compendium of Apple and Pear Diseases. 1990. St. Paul, MN: APS Press.

Content edited by: Jay W. Pscheidt on January 1, 2008

Vegetables like beans can have crown rot (collar rot) when planted in cold soils. Different varieties of beans will show different tolerances to cold soils and collar rot development.


 

Cause: Phytophthora cactorum and other species, a soilborne fungus-like microorganism. Crown rot is a disease of the rootstock portion of the tree; collar rot is a disease of the scion portion. Both are serious diseases of apple and other orchard trees in British Columbia, Washington, and Idaho, and have become a problem in Oregon orchards with clonal rootstocks, principally Malling Merton 106. Crabapple can also be infected.

The fungus survives primarily as oospores in soil, organic debris, or infected tissues. Oospores produce a swimming spore stage (zoospores) when soils are at or near saturation. Zoospores swim to and infect roots. Movement within roots to the root crown is greatest between pink bud and shoot elongation.

 

Symptoms: In early fall, an affected tree shows bronzing, purpling, or yellowing foliage of one or more limbs, accompanied by bark reddening. There is a reduction in the size of leaves and terminal growth. Examination at the root crown or collar after scraping away the soil reveals dead bark. The cambium will be orange-brown to red-brown, eventually becoming dark brown instead of white. A distinct margin may separate healthy from infected tissues. In many cases, the tree may be completely girdled before its condition is noticed. Fire blight symptoms may be similar when confined to the rootstock.

'Antonovka', 'McIntosh', and 'Wealthy' apple seedlings and M9 clonal rootstocks have shown high resistance to collar rot. Moderately resistant: MM111, M2, M7, M26, 'Golden Delicious', 'Delicious', and 'Rome Beauty'. Susceptible: MM104 and MM106.A

 

Cultural control:

  1. Plant on a raised bed to help keep water away from trunks.
  2. Avoid overirrigation.
  3. During summer, examine root crowns of trees for collar rot and scrape off diseased tissues. Leave root crowns exposed to the air until late fall.
  4. Avoid wounding root crowns. If a wound is made, keep it uncovered and open to the air for the remainder of the season.

Chemical control: Apply before symptoms appear, especially in orchards favorable for disease development. No chemical will revitalize trees showing moderate to severe crown rot symptoms. Although resistance has not been reported, alternate materials so resistant fungi do not develop quickly.

  1. Agri-Fos at 1.25 to 2.5 qt/A. Do not combine with a copper-spray program for control of other diseases. 4-hour reentry.
  2. Aliette WDG at 2.5 to 5 lb/A. Spray foliage to run off. Follow manufacturer's directions for timing of spray. Do not apply within 14 days of harvest or more than 20 lb/A per season. Do not combine with a copper spray program for control of other diseases. Phytotoxicity may result if applied within 1 week of a copper spray. 12-hr reentry.
  3. Fixed copper products. Use 4 gal solution as a drench on the lower trunk of each tree in early spring or after harvest. Do not use if soil pH is below 5.5. Not considered organic since application is to the soil.
    1. Champ Formula 2 at 2.75 pints/100 gal water. 24-hr reentry.
    2. Copper-Count-N at 4 qt/100 gal water. 12-hr reentry.
    3. Cuprofix Disperss at 5 lb/100 gal water. 24-hr reentry.
    4. Kocide DF at 4 lb/100 gal water. 48-hr reentry.
    5. Nordox 75 WG at 2.5 lb/100 gal water. 24-hr reentry.
  4. Fosphite at 1 to 3 quarts/A. Do not use copper products within 20 days of treatment and do not use spray adjuvants. May also be injected into trunk. 4-hr reentry.
  5. Phostrol at 2.5 to 5 pt/A. 4-hr reentry.
  6. Ridomil Gold SL at 0.5 pint/100 gal water. Apply diluted mixture (based on trunk size measured at 12 inches above the soil line) around each tree trunk. Apply once at planting or in spring before growth starts. Apply again in fall after harvest. 48-hr reentry.

References:
Jones, A.L. and H.S. Aldwinkle. 1990. Compendium of Apple and Pear Diseases. 1990. St. Paul, MN: APS Press.

Content edited by: Jay W. Pscheidt on January 1, 2008

 

Cause: Phytophthora cactorum and other species, a soilborne fungus-like microorganism. Crown rot is a disease of the rootstock portion of the tree; collar rot is a disease of the scion portion. Both are serious diseases of apple and other orchard trees in British Columbia, Washington, and Idaho, and have become a problem in Oregon orchards with clonal rootstocks, principally Malling Merton 106. Crabapple can also be infected.

The fungus survives primarily as oospores in soil, organic debris, or infected tissues. Oospores produce a swimming spore stage (zoospores) when soils are at or near saturation. Zoospores swim to and infect roots. Movement within roots to the root crown is greatest between pink bud and shoot elongation.

 

Symptoms: In early fall, an affected tree shows bronzing, purpling, or yellowing foliage of one or more limbs, accompanied by bark reddening. There is a reduction in the size of leaves and terminal growth. Examination at the root crown or collar after scraping away the soil reveals dead bark. The cambium will be orange-brown to red-brown, eventually becoming dark brown instead of white. A distinct margin may separate healthy from infected tissues. In many cases, the tree may be completely girdled before its condition is noticed. Fire blight symptoms may be similar when confined to the rootstock.

'Antonovka', 'McIntosh', and 'Wealthy' apple seedlings and M9 clonal rootstocks have shown high resistance to collar rot. Moderately resistant: MM111, M2, M7, M26, 'Golden Delicious', 'Delicious', and 'Rome Beauty'. Susceptible: MM104 and MM106.A

 


Cultural control:

  1. Plant on a raised bed to help keep water away from trunks.
  1. Avoid overirrigation.
  1. During summer, examine root crowns of trees for collar rot and scrape off diseased tissues. Leave root crowns exposed to the air until late fall.
  1. Avoid wounding root crowns. If a wound is made, keep it uncovered and open to the air for the remainder of the season.

Chemical control: Apply before symptoms appear, especially in orchards favorable for disease development. No chemical will revitalize trees showing moderate to severe crown rot symptoms. Although resistance has not been reported, alternate materials so resistant fungi do not develop quickly.

  1. Agri-Fos at 1.25 to 2.5 qt/A. Do not combine with a copper-spray program for control of other diseases. 4-hour reentry.
  1. Aliette WDG at 2.5 to 5 lb/A. Spray foliage to run off. Follow manufacturer's directions for timing of spray. Do not apply within 14 days of harvest or more than 20 lb/A per season. Do not combine with a copper spray program for control of other diseases. Phytotoxicity may result if applied within 1 week of a copper spray. 12-hr reentry.
  1. Fixed copper products. Use 4 gal solution as a drench on the lower trunk of each tree in early spring or after harvest. Do not use if soil pH is below 5.5. Not considered organic since application is to the soil.
  1. Champ Formula 2 at 2.75 pints/100 gal water. 24-hr reentry.
  1. Copper-Count-N at 4 qt/100 gal water. 12-hr reentry.
  1. Cuprofix Disperss at 5 lb/100 gal water. 24-hr reentry.
  1. Kocide DF at 4 lb/100 gal water. 48-hr reentry.
  1. Nordox 75 WG at 2.5 lb/100 gal water. 24-hr reentry.
  1. Fosphite at 1 to 3 quarts/A. Do not use copper products within 20 days of treatment and do not use spray adjuvants. May also be injected into trunk. 4-hr reentry.
  1. Phostrol at 2.5 to 5 pt/A. 4-hr reentry.
  1. Ridomil Gold SL at 0.5 pint/100 gal water. Apply diluted mixture (based on trunk size measured at 12 inches above the soil line) around each tree trunk. Apply once at planting or in spring before growth starts. Apply again in fall after harvest. 48-hr reentry.

References:

Jones, A.L. and H.S. Aldwinkle. 1990. Compendium of Apple and Pear Diseases. 1990. St. Paul, MN: APS Press.

Content edited by: Jay W. Pscheidt on January 1, 2008

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