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Very close up shot of wheat crop ears in field

Disease survey highlights

Defra WINTER WHEAT COMMERCIAL CROPS DISEASE SURVEY 2016


Summary highlights


  • This season, total foliar disease recorded on the top two leaves was lower than last year and is the second lowest since the survey began in 1970.
  • Zymoseptoria tritici remains the most common foliar disease. Z. tritici incidence was higher than last year, but the severity was lower.
  • Tan spot incidence was lower than last year, with 7% crops affected. As last year, tan spot was the second most common of the main foliar diseases.
  • Powdery mildew affected 7% of crops and was the third most common of the main foliar diseases.
  • Yellow rust was recorded at the highest levels since 1998, with 7% crops affected this year.
  • Brown rust affected 2% of crops this year, and was only found in three regions of the survey.
  • Septoria nodorum was not recorded in the survey this summer.
  • Cephalosporium leaf stripe was not recorded in the survey for the sixth year running.
  • The incidence of stem base fusarium (both nodal and internodal) was higher than last year. Nodal fusarium was recorded at the highest levels since 1978.
  • On the ears, 84% crops were affected with ear blight, significantly higher than last year when 26% crops were affected. Fusarium glume spot was also recorded at higher levels than last year, with 39% crops affected compared with 14% in 2015.

National and regional incidence and severity of diseases

(a) Zymoseptoria tritici, mildew and tan spot
Zymoseptoria tritici levels, although highest of all the foliar diseases, were, lower than those recorded last year. On the flag leaf this year, a mean of 0.1% leaf area was affected compared with 0.3% leaf area affected last year and this was the lowest severity of Z. tritici on the flag leaf since 2010 (when there was also 0.1% mean leaf area affected). On leaf 2, a mean of 0.7% leaf area was affected this year compared with 1.3% mean leaf area affected last year. Levels of Z. tritici this year were also markedly lower than the long-term mean (2002-2011) of 1.1% (flag leaf) and 3.7% (leaf 2) area affected. The severity of tan spot (less than 0.01% mean area of flag leaf affected and 0.02% mean area of leaf 2 affected) was slightly lower than in the previous year (when 0.02% and 0.03% mean area of flag leaf and leaf 2 were affected respectively), and was also slightly lower than the long-term mean (0.01% and 0.02% mean area of the flag leaf and leaf 2 affected respectively). Mildew levels continued to be very low this year. The incidence on both the flag leaf and leaf 2 this year were very similar to those seen in the previous year and were lower than the long-term mean of 0.03% flag leaf and 0.1% leaf 2 mean leaf area affected (Figure 1).

Figure 1 - National foliar disease levels (mean % area leaf 2 affected)

Nationally, 72% of surveyed crops were affected by Z. tritici. This was higher than last year when 61% crops were affected, but lower than the long-term mean (2002-2011) of 82% plants affected. Z. tritici remains the most common foliar disease – a position it has held since 1990. Tan spot affected 7% crops this summer, this was lower than both last year (18% crops affected) and the long-term mean (10% crops affected). It is the lowest incidence of tan spot since 2013 (when 6% crops were affected). Mildew incidence, with 7% crops affected, was lower than last year (17% crops affected) and also lower than the long-term mean (30% crops affected). (Figure 2).

Figure 2 - National foliar disease incidence, main three diseases (mean % samples affected)

Regionally, the highest incidence of Z. tritici was in the South East, where 88% crops were affected and the lowest was in the North East, where 40% crops were affected. The severity of Z. tritici was highest in the Midlands & West, where 1.25% leaf 2 was affected, and lowest in the North East, where 0.1% of leaf 2 was affected (Figure 3).

Figure 3 - Regional incidence and severity of Z. tritici

Tan spot was recorded in all regions in the survey, with the exception of the North East and the North West. The incidence of tan spot was highest in the East where 10.5% crops were affected, followed by the East Midlands, where 10.4% crops were affected. Severity was low in all regions but was highest in the South West where 0.04% leaf 2 area was affected (Figure 4).

Figure 4 - Regional incidence of tan spot

(b) Brown rust and yellow rust
In the survey this summer, the incidence of brown rust was the same as last year, with 2% crops affected. However, the incidence was lower than the long-term (2002-2011) mean of 10% crops affected. This year, brown rust was only recorded on crops in the East, East Midlands, and South East regions of the survey, with the South East having the highest incidence with 6% crops affected (Figure 5).

Last year, yellow rust was not recorded on the leaves of any surveyed crops but this year it affected 7% crops. The incidence this summer was also higher than the long-term mean of 2% crops affected and this was the highest incidence of yellow rust since 1998 (when 11% crops were affected). Yellow was recorded in crops in every region of the survey, with the exception of Yorkshire. The North West had the highest incidence of yellow rust, with 17% crops affected and also the highest severity, with of 0.05% mean area of leaf 2 affected.

Figure 5 - National foliar disease incidence, rusts (mean % samples affected)

(c) Eyespot
Mean levels of damaging eyespot (as moderate + severe symptoms) were slightly lower than last year, with 6% stems affected nationally, compared with 7% last year (Figure 6).

Figure 6 - National levels of eyespot (mean % stems affected)

Regionally, the North West had the highest levels of damaging eyespot (17% stems affected) and the South West had the lowest with 3% stems affected. Moderate symptoms were recorded in all regions in the survey and severe symptoms were recorded in all regions except the North West and the South West (Figure 7).

Figure 7 - Regional levels of eyespot (mean % stems affected)

(d) Fusarium stem base and ear disease
The incidence in 2016 (47% stems affected) was higher than last year (when 41% stems were affected) and has shown an increasing trend over the last five years. Nodal fusarium affected 43% of stems; higher than last year when 39% stems were affected and the highest proportion of stems affected with nodal fusarium since 1978 (when 46% stems were affected). The levels of nodal fusarium were mostly due to high levels of slight symptoms, but both moderate and severe symptoms were slightly higher than in the previous year, with 6.9% and 0.1% compared with 5.9% and 0.1% in 2015 respectively. Internodal fusarium affected 12% stems in the survey this year, higher than last year when 8% stems were affected. Slight and moderate levels of internodal fusarium were higher than those seen last year, with 10.6%, 1.6% compared with 7.4% and 0.7% stems affected respectively, however, severe symptoms were slightly lower than last year, with 0.03% stems affected compared with 0.1% in 2015 (Figure 8).

Figure 8 - Incidence of stem base Fusarium (mean % stems affected)

Ear blight symptoms were significantly higher than last year, with 84% samples and 21% ears affected compared with 26% of samples and 2% ears affected in 2015 (Figure 9). This is the highest incidence of ear blight since 2012, when 96% samples were affected. Glume spot was also recorded at much higher levels than last year (with 39% samples and 3% ears affected compared with 14% samples and 1% ears affected in 2015) and this is also the highest incidence of glume spot since 2012, when 45% samples and 4% ears were affected. Regionally, the North West had the highest incidence of ear blight, with 100% crops affected and the North East had the lowest (with 50% crops affected). The East had the highest incidence of glume spot, with 52% samples affected and the lowest was Yorkshire (with 14% crops affected) (Figure 9).

Figure 9 - Incidence of ear Fusarium (mean % samples affected)