Importance

Poor soil aeration, high levels of soil saturation and high mechanical resistance to root development due to soil structure degradation can increase root-rot and soil borne pathogens. They can also reduce the ability of root systems to overcome the harmful effects of pathogens resident in the topsoil. Plant diseases encouraged by degradation of soil structure include fusarium, pythium, phytophthoria, rhizoctonia, and vesicular-arbuscular mycorrhizal fungi (Department for Environment Food and Rural Affairs, Defra).

Assessment

To carry out an assessment of root diseases you will need:

1. a small spade and bucket to place the plants in
2. a bucket of water for washing out the root systems
3. additional clean water for final examination
4. a flat white tray containing water to be used for identifying and assessing root diseases
5. a magnifying glass.

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

1. Carefully dig up 3 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 (see figures below). 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.

Scoring

Scoring should be made using Figures 16 – 18 and related Tables 4 – 6.

The final score should be the one indicating the least good condition. If one score (among the scores given in tables 4 to 6) indicates poor condition, poor condition should be reported. You should score moderate conditions if the worse score among all score is moderate. You should score good conditions only when all scores are good.

Cereal cyst nematode
Rhizoctonia root rot
Take-all

Table 4. Scoring of the cyst nematode assessment

Table 5. Scoring of the Rhizoctonia root rot assessment

Table 6. Scoring of the Take-all assessment

References

Department of Primary Industries and Regional Development. https://www.agric.wa.gov.au/mycrop/monitoring-root-disease.

Department for Environment Food and Rural Affairs, defra. http://adlib.everysite.co.uk/adlib/defra/content.aspx?doc=202989&id=203609