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Very close up shot of wheat crop ears in field

Disease survey highlights

Defra Winter Wheat Commercial Crops Disease Survey 2017


Introduction


Two hundred and fifty winter wheat crops were surveyed for symptoms of disease in July 2017, with the number of crops monitored in each region being proportional to the area of wheat grown.

Summary highlights

  • This season, total foliar disease recorded on the top two leaves was higher than the last two years, primarily due to higher levels of Zymoseptoria tritici.
  • Z. tritici remains the most common foliar disease. Incidence and severity were both the highest since 2014.
  • Tan spot incidence was higher than last year, with 12% crops affected. Tan spot was the third most common of the main foliar diseases.
  • Powdery mildew affected 24% of crops and was the second most common of the main foliar diseases. Mildew levels have declined in recent years but this was the highest incidence since 2011.
  • Brown rust affected 11% of crops this year, the highest incidence since 2012. Disease severity was also increased with levels being the highest since 2007.
  • Yellow rust affected 2% crops this year, which was equivalent to the long-term average for this disease.
  • Septoria nodorum was not recorded in the survey this summer. This is the 7th time this disease has not been found in the survey in the last ten years.
  • Cephalosporium leaf stripe was not recorded in the survey for the seventh year running.
  • Overall, the incidence of stem base fusarium (both nodal and internodal) was lower than last year. However, moderate symptoms of nodal fusarium were the highest seen since 1992.
  • On the ears, 76% crops were affected with ear blight, lower than last year when 84% crops were affected. Fusarium glume spot was recorded at the highest level seen since 2011, with 47% crops showing symptoms.

National and regional incidence and severity of diseases

(a) Zymoseptoria tritici, mildew and tan spot

Z. tritici levels were higher than those seen in the last two years (Figure 1). On the flag leaf this year, a mean of 1.4% leaf area was affected compared with 0.1% leaf area affected last year and this was the highest severity of Z. tritici on the flag leaf since 2014 (when 5.9% mean leaf area was affected). On leaf 2, a mean of 2.6% leaf area was affected this year compared with 0.7% mean leaf area affected last year. Levels of Z. tritici on the flag leaf this year (1.4% mean leaf area affected) was very similar to the long-term mean (2003-2012) of 1.3% mean leaf area affected but lower on leaf 2 (2.6% this year compared with 3.6% long-term mean leaf are affected). The severity of tan spot (0.02% mean area of flag leaf affected and 0.06% mean area of leaf 2 affected) was slightly higher than in the previous year (when less than 0.01% and 0.02% mean area of flag leaf and leaf 2 were affected respectively), and was also slightly higher than the long-term mean (0.01% and 0.03% mean area of the flag leaf and leaf 2 affected respectively). Mildew levels were also slightly higher this year. The incidence of 0.02% on the flag leaf and 0.06% on leaf 2 were the highest seen since 2013 when 0.03% (flag) and 0.08% (leaf 2) mean leaf areas were recorded. However, the incidence of mildew this year was lower than the long-term mean of 0.03% on the flag leaf and 0.09% mean leaf area affected on leaf 2.

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

Nationally, 81% of surveyed crops were affected by Z. tritici (Figure 2). This was higher than both last year (72% crops affected) and 2015 (61% crops affected), but lower than the long-term mean (2003-2012) of 82% crops affected. Z. tritici remains the most common foliar disease – a position it has held since 1990. Tan spot affected 12% crops this summer, this was higher than last year when 7% crops were affected and higher than the long-term mean of 11% crops affected. Mildew incidence, with 24% crops affected, was much higher than last year (7% crops affected) but lower than the long-term mean (27% crops affected).

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

Regionally, the highest incidence of Z. tritici was in Yorkshire, where 94% crops were affected and the lowest was in the North East, where 50% crops were affected (Figure 3). The severity of Z. tritici was highest in the South West, where 9.8% leaf 2 was affected, and lowest in the North East, where 0.3% of leaf 2 was affected.

Figure 3 - Regional incidence and severity of Z. tritici

Tan spot was recorded in all regions in the survey except the North East and the North West (Figure 4). The incidence of tan spot was highest in the West Midlands where 21.7% crops were affected, followed by the South East, where 21.2 crops were affected. Severity was low in all regions but was highest in the South East where 0.2% leaf 2 area was affected.

Figure 4 - Regional incidence of tan spot

(b) Brown rust and yellow rust

In the survey this summer, the incidence of brown rust was much higher than last year, with 11% crops affected compared with 2% in 2016 (Figure 5) and was the highest incidence of brown rust in the survey since 2012, when 17% crops were affected. Within crops, 0.09% (flag) and 0.05% (leaf 2) mean leaf areas were recorded and this was the highest severity of brown rust since 2007 when 0.27% and 1.14% mean leaf areas were recorded respectively. However, the incidence this summer was the same as the long-term (2003-2012) mean of 11% crops affected. Brown rust was recorded on crops in all regions of the survey, with the exception of the North East and North West. The South East was the region with the highest incidence with 21% crops affected.

Yellow rust affected 2% crops this year and within crops less than 0.01% mean leaf area was affected on both the flag leaf and leaf 2. This was lower than last year when yellow rust affected 7% crops. The incidence this summer was also slightly lower than the long-term mean of 2.2% crops affected and within crops the severity was also lower than the long-term mean of 0.01% mean leaf area affected on both the flag leaf and leaf 2. Yellow rust was recorded in crops in most regions of the survey, it was not recorded on crops in the North East, East Midlands and South East. The North West had the highest incidence of yellow rust, with 17% crops affected.

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

(c) Eyespot

Mean levels of damaging eyespot (as moderate + severe symptoms) were very slightly higher than last year, with 6% stems affected nationally, compared with 5.6% last year (figure 6).

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

Regionally, the West Midlands had the highest levels of damaging eyespot (15% stems affected) and the East had the lowest with 3% stems affected (Figure 7). Moderate symptoms were recorded in all regions in the survey and severe symptoms were recorded in all regions except the North East, North West and the South West.

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

(d) Fusarium stem base and ear disease

The incidence of fusarium stem base in 2017 (38% stems affected) was lower than last year (when 47% stems were affected), this has been the first drop in incidence since 2014 after which it had been showing an increasing trend (Figure 8). Nodal fusarium affected 32% of stems, which was lower than last year when 43% stems were affected. Moderate symptoms of nodal fusarium (8.5% stems affected) were the highest recorded in the survey since 1992, when 12.5% stems were affected, however, slight and severe symptoms were both lower than last year with 23.4% and 0.02% stems affected with slight and severe symptoms respectively, compared with 35.7% and 0.05% stems affected respectively in 2016. Internodal fusarium affected 16% of stems which was higher than last year when 12% stems were affected. Slight, moderate and severe levels of internodal fusarium were all higher than those seen last year, with 12.9%, 3.4% and 0.08% compared with 10.6%, 1.6% and 0.03% stems affected respectively.

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

Incidence of ear blight symptoms was lower than last year, with 76% samples and 16% ears affected compared with 84% of samples and 21% ears affected in 2016 (Figure 9). Although lower than last year, it is the second highest incidence of ear blight since 2012, when 96% samples were affected. Glume spot was recorded at much higher levels than last year (with 47% samples and 5% ears affected compared with 39% samples and 3% ears affected in 2016) and this is the highest incidence of glume spot since 2011, when 57% samples and 6% ears were affected. Regionally, the West Midlands had the highest incidence of ear blight, with 91% crops affected and the North East had the lowest (with 60% crops affected). The North West had the highest incidence of glume spot, with 67% samples affected and the lowest was the North East (with 20% crops affected).

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