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Soybean
     

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Last Modified: 09-Dec-2010
Copyright © 2004, University of Kentucky, College of Agriculture, Department of Plant Pathology
     
       

Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder: Charcoal rot
Causal agent: Macrophomina phaseolina (fungus)
Signs: Many survival structures of the fungus called "microsclerotia" can be seen "peppered" in the stems and occasionally on seeds.
Symptoms: Stem infection discolores the vascular and pith tissues so that when the stem is split, black streaks can be seen as in the first row of images.
Total image number: 18
Bottom two rows of images (7 total images) are of seedling death.

         
         
 
         
 
         
 
         
                       
Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
Downy mildew
Causal agent: Peronospora manshurica (fungus)
Signs: Spores and spore-producing bodies of the fungus; see image on far right.
Symptoms: These are rather large spots for this disease which are more commonly about 3-4mm.
Total image number: 4
         
 
         
                       

Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
herbicide injury
Causal agent: something, possibly a solvent, in the herbicide “Assure II”
Signs:
Symptoms: Progression of symptoms from bleaching, reddening, then browning in blotchy to broad areas on the leaves.
See information from the University of Missouri at http://www.psu.missouri.edu/soydoc/files/weed/lipidsyn.htm
and the University of Wisconsin at
http://128.104.239.6/uw_weeds/herbinjkey/ModeOfAction/ACCase.htm
Total image number: 4

       
 
       
                       
Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
mutation
Causal agent: genetic
Signs:
Symptoms: This is a genetically abnormal plant. The various shades of green and yellow blotches on the leaves are variegations in the leaf chlorophyll. The general term for this phenomenon is called "Chimera".
Total image number: 2
       
 
       
                       

Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
acute oxygen starvation
Causal agent: Saturated soil/heat
Signs:
Symptoms: The death of these seedling plants was caused by a unique combination of
plant growth stage, saturated soil, and high heat causing a rapid death of the
below ground portion of the stem and root system.
The image of the field shows two different varieties. The variety on the left grew faster
and was not nearly as injured as the variety on the right which grew at a slower pace.
Total image number: 5

       
                         
 

Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
Bacterial pustule
Causal agent: Xanthomonas axonopodis pv. glycines (bacterium)
Signs: bacterial streaming
Symptoms: Spots range in size from small flecks to larger necrotic areas.
The center of the spots have a raised pustule on the lower leaf surface
which can appear similar to structures seen with Asian soybean rust.
Total image number: 10

 

       
                         
 

Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
Asian soybean rust
Causal agent: Phakopsora pachyrhizi (fungus)
Signs: urediniospores
Symptoms: Spots are mostly small flecks.
The center of the spots have a raised area usually on the lower surface of the leaves which can appear similar to structures seen with Bacterial pustule.
Total image number: 11

       
                         
  Plant: Soybean (Glycine max) (Fabaceae) Back to List
Disease/Disorder:
Soybean cyst nematode
Causal agent: Heterodera glycines (nematode)
Signs: cysts, larvae, eggs
Symptoms: Root infestation. Plants can be stunted depending on the total accumulation of all stresses on the plants.
Total image number: 15
       
   
       
 

       
                         
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