Leaf root and crown disease scoring – DC12 to maturity

Within the manual Protocols for experimental plot sampling, handling and processing of cereals in field experiments(external link) by G.J. Rebetzke (Greg.Rebetzke@csiro.au), A. van Herwaarden, B. Biddulph, C. Moeller, R. Richards, A. Rattey and K. Chenu.

Root and leaf disease can significantly affect cereal growth, tillering and biomass accumulation. Assessment of any obvious root and leaf diseases can be very important in later data analysis.

Regular monitoring of plots should identify any unusual reductions in plant growth, or leaf greenness. Changes can sometimes be attributed to:

a. Root diseases: Root diseases such as rhizoctonia root rot and nematodes can kill or severely reduce seedling and plant growth (Fig. 15a). Unusual reductions in plant growth usually compromise a small part of each plot. The approximate size of the affected area (in m2) and a growth score (from 0 = small growth reduction to 9 = severe growth reduction) given for the affected area. Other root or crown diseases including crown rot and take-all become apparent as dead white heads (empty of grain) during grain-filling. A score reflecting the approximate percentage of heads affected should be given where white heads are observed.
b. Leaf diseases: The most common seedling leaf disease will be yellow spot (Fig. 15b) although other leaf scalds and yellow-spotting may be apparent. Any evidence of leaf disease will require chemical control. In the meantime, an assessment may be made of the extent of leaf damage associated with a leaf disease. Again, a percentage of leaf area affected should be recorded for any damaged plots. A detailed guide to stripe rust assessment is given in Fig. 16.
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Figure 15. Below-ground diseases such as crown rot and rhizoctonia (a) and spots (b) yellow leaf spot) can substantially reduce plot vigour and yield. Take-all score of 2 (c) and 7 (d)

Fig. 16: Detailed guide to assessing leaf disease (stripe rust) in the field (after Bariana 2011)

 - File Score 1
Very resistant (VR)
– no disease
 - File Score 2
Resistant (R)
– <5% necrotic dots
 - File Score 3
Resistant to moderately resistant (R-MR)
– 10-15% necrotic stripes
– scattered and rarely sporulating
– top leaves often free from infection
 - File Score 5
Moderately resistant – Moderately susceptible (MR-MS)
– 35-45% blotchy islands with light sporulation
– can have moderate to high chlorosis and necrosis
– sporulating islands often appear all over the leave but in some cases restricted towards the leaf tip
 - File Score 6
Moderately susceptible (MS)
– 50-60% large stripes often sporulating
– stripes can turn necrotic under windy and warmer conditions
– stripes in this category remain distinct and largely uncoalesced
 - File Score 5-6
 - File Score 9
Very susceptible (VS)
– 95-100% infection
– heavy sporulation
– infection leads eventually to defoliation

Photographs and text by courtesy of Dr Harbans Bariana, University of Sydney

Other resources

Appendix 1.(external link) Text description of phenological scale, Zadoks decimal code (DC).
Appendix 2.(external link) Picture description of phenological scale, Zadoks decimal code (DC).
Zadoks JC, Chang TT, Konzak CF (1974) A decimal code for the growth stages of cereals. Weed Research 14(6),415-421. doi: 10.1111/j.1365-3180.1974.tb01084.x

Notes and troubleshooting tips


Download complete manual: Protocols for cereal field experiments_Nov2012.pdf

Health, safety & hazardous waste disposal considerations


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