Black Knot

(Apiosporina morbosa)

               
Conservation Status

IUCN Red List

not yet assessed

Black Knot

NatureServe

not listed

Minnesota

not listed

Occurrence

Agricultural pest, widespread

Season

Year-round; sporulation in wet weather

Habitat/Hosts

American plum, black cherry, and other Prunus species


Identification

Black Knot is a symptom, not the form, of a parasitic fungus, Apiosporina morbosa, infecting living plants of the Prunus genus.

Knots (galls) are black, irregular, bumpy swellings clasping and sometimes surrounding the twigs and branches, sometimes the trunk, of cherry and plum trees and shrubs. They are elongated, furrowed, cracked, ½ to 12 long, and to 1 in diameter.

Spores are produced during extended rainfalls of six hours or more when the temperature is between 60° and 80°F. They are spread by wind and by rain splashing. Where spores land on current season’s growth or wounded tissue an infection occurs. Growth the first year is very slow. The infection first appears in the late summer as a small, warty, greenish-brown or light brown swelling. The fungus overwinters in this state. The following spring the swelling turns olive green and velvety. Over this growing season (the second year of infection) the knot grows rapidly and has a corky texture. Several knots may merge into a single large knot. Eventually, the knot turns black, hard, and brittle. The Black Knot is usually the first symptom of the disease that is noticed. Tissue toward the center of the knot often dies after two years and is invaded by boring insects. The dead gall tissue is colonized by another fungal parasite, Trichothecium roseum, that gives the knot a whitish or pinkish appearance.

Young infected twigs die the first year of infection. Older branches may last several years. Infections cause the host to lose vigor and may eventually be fatal.

 
Similar
Species

 


Distribution Distribution Map  

Sources: 4, 7, 26, 29.


Comments

 


Taxonomy

Division:

Ascomycota (sac fungi)

 

No Rank:

saccharomyceta

 

Subdivision:

Pezizomycotina

 

No Rank:

leotiomyceta

 

No Rank:

dothideomyceta

 

Class:

Dothideomycetes

  No Rank:

Dothideomycetes incertae sedis

 

Order:

Venturiales

 

Family:

Venturiaceae

 
Synonyms

Botryosphaeria morbosa

Cucurbitaria morbosa

Dibotryon morbosum

Otthia morbosa

Plowrightia morbosa

Sphaeria morbosa

 
Common
Names

Black Knot


 

 

 

 

 

 

 

       

Visitor Photos

   
Share your photo of this fungi or lichen.

       
       
       
       

MinnesotaSeasons.com Photos

   

On a Twig

  Black Knot   Black Knot
       
  Black Knot    
       

On a Trunk

  Black Knot   Black Knot
       
  Black Knot   Black Knot
       
       

 

Camera

     

Slideshows

   
  Black Knot Disease
Andree Reno Sanborn
 
  Black Knot Disease  
 
About

Disease of apple and cherry.

 
     

 

slideshow

     

Visitor Videos

   
Share your video of this fungi or lichen.

     
     

Other Videos

 
  Black Knot on Cherries and Plums - James Blake
clemsonpsa
 
   
 
About

Uploaded on Jul 19, 2009

Hi, I'm James Blake, Director of the Clemson Extension Home & Garden Information Center. Today we're looking at a disease known as black knot.

Were along the edge of the Clemson University Experimental Forest looking at a wild black cherry with some strange black growths on the twigs. This disease is known as black knot caused by the fungus Apiosporina morbosa. It infects cherries and plums.

The fungus can infect green shoots but can also enter through wounds. Infection leads to these long, rough galls on the twigs and branches and can even infect the trunks of trees. These galls can range in size from an inch to more than 20 inches. These galls can form on one side of a branch or can encircle the entire branch. When infection circles the entire branch or twig it leads to death beyond the point of the gall.

The duration of the complete cycle of this disease is normally 2 years. After infection occurs in the spring, swellings appear in the fall on the current seasons growth. After being dormant during the winter, the fungus resumes growth in spring and the bark splits revealing olive-green fungal tissue covered with spores. These galls turn darker during the summer and fall and then turn hard and black during the winter. In the following spring, another spore stage is produced on the black knots that starts new infections.

Management of black knot begins with the selection of resistant cultivars. If any galls form on susceptible varieties these galls should be removed 4 inches below the point of the gall. All infected plant material should be destroyed.

For more information on gardening, landscaping, insect and disease problems on your plants, visit the Home & Garden Information Center web site at www.clemson.edu/hgic.

 
     
  Black knot fungus tutorial
BuckthornMN
 
   
 
About

Published on Jan 7, 2013

Buckthorn versus cherry trees - black knot fungus grows on cherry trees but not on buckthorn. Learn to Identify and remove black knot fungus from native cherry trees in your woodland. Get rid of buckthorn - not cherry trees

 
     
  BLACK KNOT FUNGUS!
bushcraftbartons
 
   
 
About

Published on Mar 27, 2012

NOTE: 4 days after visiting the shelter good weather came by and started to really melt. Visited a forest that was facing South and not North like my shelter. What a difference. I fell upon something I felt I could share.

Showing that this fungus is not Chaga even though they look similar..Please visit our website http://bushcraftbartons.com/

 
     
  Black Knot
alcoopextensionvideo
 
   
 
About

Uploaded on Feb 25, 2010

Dr. Scott Enebak Auburn University School of Forestry & Wildlife Sciences, discusses the characteristics of common forest diseases.

 
     

 

Camcorder

         

Visitor Sightings

   
Share your sighting of this fungi or lichen.

     
     
 

MinnesotaSeasons.com Sightings

   

Afton State Park

Banning State Park

Big Stone Lake State Park

Blaine Preserve SNA

Blanket Flower Prairie SNA

Blue Devil Valley SNA

Buffalo River State Park

Bunker Hills Regional Park

Carpenter St. Croix Valley Nature Center

Cedar Mountain SNA

Chamberlain Woods SNA

Chimney Rock SNA

Cleary Lake Regional Park

Clinton Falls Dwarf Trout Lily SNA

Des Moines River SNA

Elm Creek Park Reserve

Englund Ecotone SNA

Falls Creek SNA

Felton Prairie SNA
Bicentennial Unit

Forestville/Mystery Cave State Park

Fort Ridgely State Park

French Regional Park

Frenchman’s Bluff SNA

Glacial Lakes State Park

Glendalough State Park

Great River Bluffs State Park

Hastings SNA

Hayes Lake State Park

Helen Allison Savanna SNA

Hyland Lake Park Reserve

Itasca State Park

John A. Latsch State Park

Kilen Woods State Park

King’s and Queen’s Bluff SNA

La Salle Lake SNA

Lake Carlos State Park

Lake Elmo Park Reserve

Lake Louise State Park

Lake Rebecca Park Reserve

Lebanon Hills Regional Park

Leif Mountain

Lost Valley Prairie SNA

Malmberg Prairie SNA

Mary Schmidt Crawford Woods SNA

Mille Lacs Kathio State Park

Mille Lacs WMA

Minnesota Valley State Recreation Area
Lawrence Unit

Moose Lake State Park

Mound Prairie SNA

Murphy-Hanrehan Park Reserve

Nerstrand Big Woods State Park

Old Mill State Park

Oronoco Prairie SNA

Oxbow Park & Zollman Zoo

Pigeon River Cliffs

Pin Oak Prairie SNA

Pine Bend Bluffs SNA

Prairie Creek Woods SNA

Prairie Smoke Dunes SNA

Rice Lake Savanna SNA

Rice Lake State Park

Ripley Esker SNA

River Terrace Prairie SNA

Rushford Sand Barrens SNA

Sakatah Lake State Park

Savage Fen SNA

Scenic State Park

Split Rock Creek State Park

Spring Lake Park Reserve

Sunfish Lake Park

Terrace Oaks West

Townsend Woods SNA

Twin Lakes SNA

Uncas Dunes SNA

Upper Sioux Agency State Park

Vermillion Highlands

Whitetail Woods Regional Park

Whitewater State Park

Whitney Island SNA

Wild River State Park

William O’Brien State Park

Woodland Trails Park

Zumbro Falls Woods SNA


 

 

Binoculars

Last Updated:

About Us | Privacy Policy | Contact Us | © 2017 MinnesotaSeasons.com. All rights reserved.