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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


  • In 2016, total foliar disease severity recorded on the top two leaves was lower than in 2015 and is the second lowest since the survey began in 1970.
  • Zymoseptoria tritici remained the most common foliar disease. Z. tritici incidence was higher than the previous year, but the severity was lower.
  • Tan spot incidence was lower than in 2015, with 7% crops affected. As in 2015, 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.
  • Brown rust affected 2% of crops in 2016 and was only found in three regions of the survey.
  • Septoria nodorum was not recorded in the survey this summer. This pathogen has become very scarce in occurrence having been found in only one surveyed crop (in 2015) since 2009.
  • 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 the previous year. Nodal fusarium was recorded at the highest levels since 1978.
  • On the ears, 84% crops were affected with ear blight, significantly higher than in 2015 when 26% crops were affected. Fusarium glume spot was also recorded at higher levels, with 39% crops affected compared with 14% in 2015.
  • As in previous years, the majority of crops were sown between 20th September and the 10th October.
  • Surveyed crops received an average of 3.7 fungicide applications, slightly higher than last year when crops received an average of 3.6 fungicide applications.
  • There was only 1 crop that was not treated with any fungicides – this was an organic crop.
  • There was an increase in the use of SDHI fungicides for the sixth year running. In 2016, 98% of crops received at least one treatment containing an SDHI fungicide. Risks of further development of resistance in Z. tritici to SDHI fungicides therefore remains very high.
  • The proportion of crops receiving sprays at key spray timings was similar to last year, with the exception of T0 and T4. At T0, 35% of crops received a spray, compared with 77% crops in 2015. At T1, 96% crops received a spray compared with 99% crops in 2015. At T2, 94% crops received a spray compared with 91% in 2015. At T3, 86% crops were sprayed this year compared with 80% in 2014 and at T4, 9% crops were sprayed this year compared with 3% in 2015. This is the highest proportion of crops treated at T2 and T3 since the survey began, again increasing risks of further resistance development in target pathogens.

National and regional incidence and severity of diseases

(a) Zymoseptoria tritici, mildew and tan spot
Z. tritici levels, although highest of all the foliar diseases, were lower than those recorded in 2015. On the flag leaf, a mean of 0.1% leaf area was affected compared with 0.3% leaf area affected in the previous 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 compared with 1.3% mean leaf area affected in the previous year. Levels of Z. tritici 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. Disease levels on both the flag leaf and leaf 2 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 in 2015 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 was lower than in 2015 (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 in 2015 (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 summer of 2016, the incidence of brown rust was the same as in 2015, 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).

Yellow rust was not recorded on the top two leaves of any surveyed crops at GS75 in 2015 but affected 7% crops in 2016. The incidence in 2016 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) in 2016 were slightly lower than in 2015, with 6% stems affected nationally, compared with 7% in the previous 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 of stem base fusarium symptoms in 2016 (47% stems affected) was higher than in the previous year (when 41% stems were affected) and the disease has shown a significant increasing trend over the last five years (Figure 8). Nodal fusarium affected 43% of stems; higher than in 2015 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, higher than in 2015 when 8% stems were affected. Slight and moderate levels of internodal fusarium were higher than those seen in 2015, 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 - Incidence of stem base Fusarium (mean % stems affected)

Ear blight symptoms were significantly higher in 2016, with 84% samples and 21% ears affected compared with 26% of samples and 2% ears affected in 2015. This is the highest incidence of ear blight since 2012, when 96% samples were affected (Figure 9). Glume spot was also recorded at much higher levels in 2016 (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 - Incidence of ear Fusarium (mean % samples affected)

Agronomic Practice

(a) Cultivar use

Thirty-nine different cultivars of winter wheat were encountered during the 2016 survey (Figure 10). JB Diego was the most popular variety for the second year running and it accounted for 12.9% of the sample. Skyfall was the second most popular accounting for 12.4% of the sample. Of the ten most popular cultivars (see Figure 10), the highest average level of Z. tritici was recorded on KWS Santiago with 2.95% of leaf 2 affected. The lowest was on Skyfall, with 0.04% of leaf 2 affected. Skyfall was also the cultivar with the lowest average mean area of leaf 2 affected with Z. tritici in 2015. Of the varieties in the top ten most popular, KWS has the lowest rating for resistance to Z. tritici (4) whereas Skyfall has one of the highest (6).

Figure 10 – Severity of Z. tritici on the main cultivars (mean per cent area leaf 2 affected) and popularity of cultivars.

In the ten most popular cultivars of 2016, the incidence of tan spot was highest in Revelation, with 25% samples affected (Figure 11). This was followed by KWS Santiago which had 17.0% samples affected. Tan spot was recorded in six of the ten most popular cultivars in 2016, with Skyfall, Evolution, Grafton and Dickens being the four most popular varieties where tan spot was not recorded. There are no published ratings for varietal resistance to tan spot.

Figure 11 – Incidence of tan spot on the main cultivars (per cent samples affected) and popularity of cultivars.

A comparison of disease severity on the ten most popular cultivars showed that Skyfall had the lowest total foliar disease severity with 0.07% area of leaf 2 affected (Figure 12) and the highest was KWS Santiago, with 3.1% area of leaf 2 affected. Skyfall was also the cultivar with the lowest total foliar disease severity in 2015 (when there was also 0.07% area of leaf 2 affected). Mildew and Z. tritici were most severe on KWS Santiago (rated 4 for both diseases) and yellow rust and brown rust most severe on Crusoe. Z. tritici was the only foliar disease present on leaf 2 in all ten most popular cultivars. Levels of moderate + severe eyespot were highest on Dickens (rated 4 for eyespot resistance), with an average of 14% stems affected, and the lowest on Crusoe (rating 5), with an average of 0.9% stems affected. Levels of eyespot disease on Crusoe appear very low compared to the rating, but the low levels on Skyfall, Revelation and Grafton (all below 5% stems with moderate + severe symptoms) may be evidence that the Pch1 Rendezvous gene that these varieties are believed to carry is proving effective in reducing disease levels in the field. The highest severity of Fusarium stem base symptoms was on Grafton, with an average of 20% stems affected with moderate or severe symptoms. Crusoe was the next highest, with an average of 11.1% stems affected. Evolution and JB Diego were the least affected, with an average of 6.0% stems affected by moderate and severe symptoms on both cultivars.

Figure 12 – Total foliar disease levels (average per cent leaf 2 affected), eyespot severity (moderate + severe categories) and stem base Fusarium (moderate + severe categories) for the most popular cultivars.

(b) Sowing date

The majority of crops in surveyed in the 2015/16 season i were sown between the 20th September and the 10th October (Figure 13). This was higher than in 2014/15 and this period has been the peak timing for sowing in recent years. Eight per cent of crops were drilled before the 20th September – this was a slightly lower proportion than in 2014/15 when 11% crops were sown during this period. Thirty-six percent of crops were sown between the 20th and 30th September, this was slightly higher than in the previous year when 30% crops were drilled at this time and is the highest proportion of crops drilled at this time since 2013/14 (38% crops). Between the 1st and the 10th October, 28% of crops were drilled, this was slightly lower than last year (29% crops). Seventeen per cent crops were drilled between the 11th and 20th October, which was higher than in 2014/15 when 11% crops were sown between these dates. The proportion of crops sown between the 21st and the 31st October was 7%, This was lower than last year when 12% crops were drilled during this period. The proportion of crops drilled after 31st October was 4%, this is the lowest proportion of crops sown at this time since 2011/12 (3% crops).

Figure 13 - Sowing dates of survey crops (%)

The overall eyespot index for crops was lower than in 2015 at the earlier three sowing timings, and higher at the later three sowing timings (Figure 14). The eyespot index for crops sown between the 11th and 20th October was the highest for this sowing period since 2008. For crops sown between 21st and 31st October, the eyespot index was the highest since 2006 and for crops sown after 31st October, the index was the highest since 2000. Historically, there has been a trend for eyespot to be less severe on crops sown after 10th October, in 2016 however, the opposite has occurred.

Figure 14 – Eyespot index with sowing dates

(c) Fungicide use

Surveyed crops received an average of 3.7 fungicide applications per crop in 2016, slightly higher than in 2015 when crops received an average of 3.6 applications. This is the second highest average number of fungicide treatments since the survey began in 1970 (2014 was the highest with an average of 3.8 applications per crop). At both the T0 (March) and T1 treatment timing (target leaf 3 fully emerged), the number of crops receiving a spray was lower than it was in 2015 (Figure 15), however, the number of crops receiving a spray at T2 (target flag leaf emergence) , T3 (target ear emergence) and T4 (flowering complete) was higher. At both the T2 and T3 timing, the average numbers of crops receiving a spray was the highest since the survey began and for T4, it was the highest number since 1995.

Figure 15 – Fungicide applications during the growing season.

  • The use of chlorothalonil, from the phthalonitrile group, was the third most used fungicide group in the survey in 2016 (Figure 16). Although the proportion of crops treated with chlorothalonil dropped markedly in 2011, its use has increased steadily again over the last five years, with 2016 seeing the highest proportion of crops treated since the survey began. In 2016, chlorothalonil treated crops received an average of 1.9 applications/crop, this was the lower than last year when crops received an average of 2.2 applications/crop. Chlorothalonil use in all treated crops averaged 1.8 applications per crop, also lower than in 2015 (2.1 applications/crop).
  • At key stage T0, chlorothalonil use decreased significantly with 30% of crops receiving an application , , compared with 70% in 2015 and 41% in 2014. The proportion of crops receiving T1 and T2 applications containing chlorothalonil increased, with 83% and 49% of crops respectively receiving an application, compared with 82% and 45% in 2015. At timing T3, there was a slight decrease in chlorothalonil use; down to 13% crops treated from 14% in 2015. Two per cent of crops received an application containing chlorothalonil at T4, this was higher than in 2015 when 0.3% received an application at this timing.
  • DMI (demethylation inhibitor) fungicides, comprising the imidazole and triazole chemical groups, were the most often used fungicide group, with 100% of treated crops receiving at least one application, this was the same proportion in 2015 and a slight increase from 2014, when this figure was 99.7% crops. DMI treated crops received an average of 3.0 applications/crop which was slightly lower than the 3.3 applications/crop recorded in 2015.
  • DMI applications at each key spray timing in 2016 were generally higher than those seen in 2015, with the exception of T0 and T1 where there was a decrease in use. At T0, the proportion of crops receiving an application containing a DMI fungicide dropped from 62% in 2015 to 28% in 2016. At T1, 92% of fungicide treated crops received an application containing a DMI fungicide, which was the lower than 2015 when it was 96% crops. The proportion of crops receiving T2 and T3 applications containing DMI increased slightly from 90% and 79% of crops respectively in 2015, to 94% and 84% respectively in 2016. At T4 the proportion of crops receiving an application of DMI also increased from 3% of fungicide treated crops receiving an application in 2015 to 9% in 2016. Eighty-five per cent of crops received 3 or more applications per crop containing at least one DMI product per application, which was the same proportion of crops as in 2015. There were 8% of DMI treated crops which received 5 or more applications containing at least one DMI product per application - this figure was 2% crops in 2015.
  • Since the use of fungicides from the strobilurin group peaked in 2003their use has been in steady decline ever since. There was however a slight increase in use in 2016 - with 57% crops receiving at least one application containing a strobilurin (compared with 53% crops in 2015). Crops treated with a strobilurin received an average of 1.4 applications per crop, this was slightly higher than theaverage of 1.2 applications per crop recorded in 2015.
  • Use of strobilurin applications was similar to 2015 at all timings with the exception of T2, where there was a large increase in use. In 2016, 4% crops received a fungicide application containing at least one strobilurin at T0, 23% at T1, 28% at T2, 23% at T3 and 0% at T4. This compares with 5% at T0, 22% at T1, 15% at T2, 21% at T3 and 1% at T4 in 2015. Where strobilurins were applied to crops, this was most often as a single treatment (64%). Thirty-five percent of crops received two strobilurin applications per crop and 1% received three.
  • There was an increase again this year in the use of SDHI (succinate-dehydrogenase inhibitor) fungicides for the fifth year running, and in 2016 it became the second most used fungicide group. Ninety-eight per cent of crops received at least one application of SDHI fungicides in 2016, this compares with 28%, 23%, 23%, 50%, 64%, 85%, 92% and 94% from 2008 – 2015 respectively. SDHI treated crops received an average of 1.8 applications/crop, which was the same average number of applications as in 2015.
  • There was an increase in SDHI use at all spray timings, with the exception of T0 and T4. The most common spray timing for this fungicide group was T2, when 90% crops were treated at this time (84% in 2015), followed by T1 when 72% crops were treated (69% in 2015). At T0, T3 and T4, there were 1% 10% and 0.4% crops treated with an SDHI respectively. Seventy-eight per cent of crops received 2 applications containing at least one SDHI product per application, a slight increase from 2015 when 73% crops received 2 applications.
  • The proportion of crops receiving morpholine fungicides was higher than in previous years. In 2016, 25% of treated crops received at least one application, compared with 24% in 2015, 24% in 2014 and 25% in 2013. As in 2015, the most common spray timing was T1; 12% of crops treated at this time received applications of fungicides from this group, which was slightly lower than the previous year (14%), this was followed by T2 with 8% (4% in 2015). Morpholine fungicides were used on 2% of crops at T4, whereas they were not applied to any crops at this timing in 2015. On average, crops received 1.3 applications per crop of morpholine fungicides, which is slightly higher in 2015 when crops received an average of 1.2 applications per crop.

Figure 16 - Fungicide use: per cent of treated crops receiving applications from the major fungicide groups and the ai. chlorothalonil post emergence. * Includes the chemical groups morpholines, piperidines and spiroketalamines (as reductase/isomerase inhibitors).

Figure 17 - Fungicide use: per cent of all crops treated at the key timings with the major fungicide groups and the ai. chlorothalonil post emergence. * Includes the chemical groups morpholines, piperidines and spiroketalamines (as reductase/isomerase inhibitors).