Monitoring root disease

Plant root diseases are one of the main factors responsible for poor crop yields.

Roots of affected plants are blackened and brittle and break easily, and are black to the core not just on outer surface.
Roots of affected plants are short with characteristic pinched ends – ‘spear tips’.
Blackening of sub-crown internode in extreme cases

Why assess plant root disease?

It is important that plant root diseases are correctly identified and the level of severity assessed so that appropriate strategies for controlling disease can be developed and implemented – in order the limit future crop yield loss.

Assessing root disease

  1. To carry out an assessment of root diseases you will need?
  2. A small spade and bucket to place the plants in
  3. A bucket of water for washing out the root systems
  4. Additional clean water for final examination
  5. A flat white tray containing water to be used for identifying and assessing root diseases
  6. A magnifying glass

In order to assess/diagnose plant diseases, the following methods are used:

  1. Carefully dig up 10 plants along the crop monitoring path, making sure that soil is left intact around the root system of the plant.
  2. For cereal root diseases, rate the severity of root disease identified. (insert disease cartoons) For other diseases, indicate whether or not they are present in the crop.  
  3. At each collection point, visually assess the area of crop affected by the disease.
  4. Calculate an average area affected for the 10 sites observed.

Interpreting root disease assessment

Ratings of 1 or 2 for cereal root diseases’ indicate that an economic yield loss is occurring. It will be necessary to review your agronomic management, in particular your selection of crop species and variety when planning future crop rotations.

Other agronomic factors such as crop establishment techniques, control volunteer hosts and the nutritional status of crops also need to be taken into consideration when developing appropriate disease management strategies for future crop rotation programs.

Roots affected by cereal cyst nematode

Roots affected by cereal cyst nematode

Cereal cyst nematode

Score

Root length normal on a severity scale of 0 - 5, rating is 0

0

Roots are 40 % shorter than healthy roots, on a severity scale on 0 - 5 rating is between 1 - 1.5

1

Roots are 60 % or more shorter than healthy roots, on a severity rating of 0 - 5 scoring 2 or more

2

Roots affected by Rhizoctonia root rot

Roots affected by Rhizoctonia root rot

Rhizoctonia

Score

No roots are shortened

0

Up to 25% of the roots are shortened

1

More than 25% of roots are shortened

2

Roots affected by Take-all

Roots affected by Take-all

Take-all

Score

No lesion visible

0

1 or 2 main seedling roots have lesions

1

3 or more seedling roots have lesions

2

 

 

Page last updated: Thursday, 15 January 2015 - 9:30am