Control options for STNB across WA farming systems

Author: | Date: 29 Feb 2016

Hills AL1, G Thomas2, A Grey3, M Field 4, R Horbury5, K Jayasena6, C Beard7 and B Paynter8

DAFWA Esperance1, South Perth2, Albany6, Geraldton7, Northam8; ConsultAg Narrogin3, Bayer Northern5, Farm & General Esperance 4

Key messages

  • Grain yield response to fungicide application occurred in more than half (58%) of trials analysed. Grain yield gain from STNB control ranged from 0.19 to 2.18t/ha (5 – 59%) of the untreated yield. Grain screenings reduced by a third and there were also improvements in grain weight, hectolitre, brightness and protein levels.
  • Double applications of fungicide, with the first made at stem extension, gained the greatest yield responses in the medium and high rainfall areas.
  • Variety yield response reflects the disease rating – the highest gains are with SVS varieties.
  • Spring rainfall, particularly rainfall and number of rainy days in September, determines the likelihood of a yield response to fungicide application. Growers in the medium and low rainfall areas need to take the spring rainfall outlook into account when deciding if a second fungicide application is necessary – in a dry spring there is no additional benefit from a second application.
  • Propiconazole and Prosaro® performed comparably in nearly all situations where they were head to head.

Aims

Just over 98% of the area sown to barley in Western Australia in 2015 was to a variety that is rated susceptible or worse for spot type net blotch (STNB). While nearly all the barley varieties grown in WA are susceptible to STNB, the dominance of Hindmarsh , rated SVS, has exacerbated the problem. Barley on barley rotations have increased in prevalence, raising the disease pressure further and leading to situations where high levels of early infections occur.

This study brought together the results of many different small plot trials from WA across 17 years. Its aims were to:

  1. Determine what the yield and grain quality benefits are from controlling STNB.
    1. What is the most effective fungicide strategy to control STNB?
    2. Of the commonly used fungicides, is any option better than another?

Method

This study used results from 24 small plot trials (1998–2015) where STNB was the primary disease present (Table 1). Most trials were located in the medium and high rainfall zones. Three trials were opportunistically set up in farmer established paddocks after disease appeared. Trial designs were randomised blocks or split plots with either three or four replicates (apart from two with six). Trials were sown into barley stubble, adjacent to barley stubble or had barley stubble spread after sowing while others followed canola (one), wheat (one) or pasture (one). Some trials contained a single variety while others had more. Fungicides and their times of application varied between trials.

Trials were selected on the basis that STNB was the only disease recorded or it was by far the dominant disease at a site. Disease assessments scored the percentage of disease present on the top leaves of ten randomly selected plants per plot (one trial assessed five plants/plot) with the disease levels at grain filling stage or the assessment nearest to this shown (Table 1). The leaves assessed always included flag-1 (F-1) and flag-2 (F-2) but some assessments included flag (F) leaf and others flag-3 (F-3) so that the Top 3 leaves is either F to F-2 or F-1 to F-3.

Grain yield was taken using small plot harvesters. Plot widths and lengths varied with widths of approximately 1.75m and lengths of 10-20m. The Genstat (VSNI, 2014) statistical package was used to analyse site data (apart from two sites) using the 95% level of confidence unless specified. Rainfall information is from the site, BOM, DAFWA and patch point data sets.

Grain quality data was not available for all trials or only some characteristics were measured. Grain size (2.5mm screenings) and hectolitre weight were usually reported (17 sites) and others also had grain weight (13 sites), grain brightness (12 sites) and grain protein (14 sites).

Results refer to treatment responses – results of full control applications (three or more fungicides) were excluded.

Table 1. Trial details for 24 sites. Barley variety abbreviations are Bass (Bs), Baudin (Ba), Buloke (Bu), Compass (Cs), Dash (D), Fathom (F), Gairdner (Ga), Granger (Gr), Hamelin (Ha), Hindmarsh (Hi), La Trobe (LaT), SY Rattler (R), Scope (Sc), Stirling (St), Vlamingh (V) and Wimmera (W).

Trial

Owner

Location

Rainfall zone

Sowing date

Barley variety

Rotation

15WE03

Bayer

Cunderdin

M

1/6/2015

LaT

diseased stubble spread

15WE01

Bayer

Dandaragan

H

25/5/2015

Bs

diseased stubble spread

15CAg-Stubble

ConsultAg

Corrigin

M

14/5/2015

Sc

barley

15CAg-Burnt

ConsultAg

Corrigin

M

14/5/2015

Sc

stubble burnt

15ES13

DAFWA

Wittenoom Hills

M

12/5/2015

Hi, LaT, Sc, Cs, R, F, Gr, D

barley

15ES11

DAFWA

Gibson

H

8/5/2015

Hi, LaT

barley

15ES39^

DAFWA

Coomalbidgup

H

26/4/2015

Sc

barley

15Farm&Gen^

Farm&General

Coomalbidgup

H

17/5/2015

LaT

pasture

15KA34

DAFWA

Arthur River

H

25/5/2015

Hi, Bs

barley

15ME11

DAFWA

Nungarin

L

11/5/2015

Sc, Hi

barley

15ME24

DAFWA

Nungarin

L

11/5/2015

Hi, LaT, Sc, Cs, R, F, Gr, D

barley

10AV03

DAFWA

Meckering

M

29/5/2009

Ba, Bs

barley

09AV03

DAFWA

Meckering

M

26/5/2010

Ba, Bs

barley

09WC39

Bayer

Meenar

M

?/6/2009

Hi

barley

06GE07

DAFWA

Mingenew

M

1/06/2006

Ha

barley

05ES05 TOS1

DAFWA

Salmon Gums

L

30/5/2005

Ba, Bu, V, St, Ha + 15 lines

barley

05ES05 TOS2

DAFWA

Salmon Gums

L

14/6/2005

Ba, Bu, V, St, Ha + 15 lines

barley

05ES06

DAFWA

Gairdner

H

25/5/2005

Ba, V

canola

03GE06^

DAFWA

Yuna

M

na

St

wheat

01AL03

DAFWA

South Stirling

H

26/5/2001

Ga

barley

00ES29

DAFWA

Gibson

H

8/5/2000

Ga

barley

99AL5

DAFWA

Wellstead

H

8/6/1999

Ga

barley stubble adjacent

99ES1

DAFWA

Scaddan

M

24/5/1999

Ga

barley stubble adjacent

98AL7

DAFWA

Wellstead

H

3/6/1998

Ga

diseased stubble spread

^Established opportunistically in a grower’s crop.

Results

There was a reasonable range of disease levels represented in the study; of 24 trials, seven had an average untreated disease level of less than 10% of leaf area diseased (LAD of the top three leaves), seven trials had low to moderate levels (10 – 25% LAD), seven trials had moderate to high levels (25 – 50% LAD) and three trials had very high levels of disease (greater than 50% of LAD) (Table 2). In all trials, the leaf disease severity significantly decreased with fungicide application, including four sites where STNB occupied less than four per cent of leaf area (Table 2).

Table 2. In season trial details including rainfall totals for the months shown, zadoks growth stage of disease assessment, yield response (%) to fungicide application (best treatment response excluding full control), grain yield (kg/ha of untreated barley), STNB % of disease present on top 3 leaves of untreated barley, screenings (%<2.5mm of untreated barley). ns = not significant, na = not available.

 

 

Rainfall (mm)

 

 

Untreated (Nil fungicide)

Trial

Location

May-Oct

Aug-Sept

Growth stage

Yield response (%)

Grain yield (kg/ha)

STNB       (% Top 3)

Screenings %<2.5mm

15WE01

Dandaragan

227

64

Z75

ns

2 670

6

na

15WE03

Cunderdin

167

53

Z75

ns

2 810

3

na

15ES11

Gibson

320

126

Z80

24

4 166

11

14

15ES13

Wittenoom Hills

301

105

Z76

27

4 100

18

35

15ME11

Nungarin

183

52

Z75

ns

2 800

40

12

15ES39

Coomalbidgup

305

119

Z73

11

4 017

10

24

15ME24

Nungarin

183

52

Z75

ns

3 118

40

32

15KA34

Arthur River

160

67

Z65

ns

2 460

10

na

15CAg-Stubble

Corrigin

160

70

Z38

10^

2 240

20

45

 

 

Rainfall (mm)

 

 

 

Untreated (Nil fungicide)

Trial

Location

May-Oct

Aug-Sept

Growth stage

Yield response (%)

Grain yield (kg/ha)

STNB       (% Top 3)

Screenings %<2.5mm

15CAg-Burnt

Corrigin

160

70

Z38

ns

2 791

29

36

15Farm&Gen

Coomalbidgup

323

114

Z85

14

5 600

28

na

10AV03

Meckering

125

30

Z76

ns

1 564

6

38

09AV03

Meckering

251

72

Z75

ns

3 173

58

12

09WC39

Meenar

260

79

Z65

43

2 530

48

na

06GE07

Mingenew

151

84

Z83

ns

1 230

54

18

05ES06

Scaddan

278

91

Z73

11

3 993

13

4

05ES05 TOS1

Salmon Gums

227

74

Z84

5

3 782

2

3

05ES05 TOS2

Salmon Gums

227

74

Z64

6

3 728

1

4

03GE06

Yuna

273

126

Z49

23^

2 600

15

23

01AL03

South Stirling

247

103

Z73

59

2 940

54

16

00ES29

Gibson

201

82

Z77

32

3 900

99

42

99ES1

Scaddan

195

60

Z71

20

2 630

9

30

99AL5

Wellstead

221

58

Z71

24

3 000

3

14

98AL7

Wellstead

279

105

Z75

ns

1 900

46

na

^Significant at p=0.08;

Grain yield

Fifty eight per cent of sites (14/24) had a grain yield response to treatment applications of fungicides. The average grain yield of responsive sites was 3.58 t/ha while the average yield of non-responsive sites was 2.36 t/ha. Across all sites the average untreated yield was 3.07 t/ha which reflects the tendency of these trials to be in the medium to high rainfall areas (20/24 sites). Yield responses from controlling STNB ranged from five to 59% (0.19 – 2.18 t/ha) of the untreated yield with an average of 0.44 t/ha or 22% (Tables 2, 3). Yield responses to fungicides were higher (0.66 t/ha) and occurred more frequently (in 70% of trials) in the high rainfall zone than in the medium (0.35 t/ha, 50% of sites) or low rainfall zones (0.10 t/ha, 50% sites) (Table 3).

Table 3. Grain yield response (%) to STNB control of trial sites grouped by annual rainfall where high is >450mm, medium 350 – 450mm and low < 350mm. The average yield responses to two scenarios are shown; over all sites and at those that showed a significant yield response. Also shown are the number of sites in each rainfall zone, the number that had a significant yield increase and the range of the yield responses (% untreated).

Rainfall zone

No. sites

No. sites responsive

Responsive sites (%)

Response range (%)

Yield  (t/ha)

All sites

Responsive only

High

10

7

70%

11 - 59

0.66

0.94

Medium

10

5

50%

10 - 43

0.35

0.71

Low

4

2

50%

5 - 6

0.10

0.20

Overall

24

14

58%

5 - 59

0.44

0.70

Just over half of the sites (14/24) in this study experienced relatively low rainfall in the spring period (August – September), which was defined as less than 80mm in total. Sites that did not have a yield response to STNB control all had low spring rainfall. While it was possible to get a yield response in a dry spring (Table 4), it was less likely (43% chance or 6/14 sites) than where rainfall exceeded 80mm (80% chance or 8/10 sites). The magnitude of the yield response also increased substantially when sites received more than 80mm over spring (Table 4).

Table 4. Grain yield response (t/ha) to the application of fungicides based on the amount of spring rainfall where low is <80mm; adequate is >80 mm during August - September.

Trials

Spring rainfall

Low

Adequate

All sites

0.21 t/ha

0.76 t/ha

Responsive only

0.49 t/ha

0.95 t/ha

Regression analysis showed that yield response (kg/ha) to control of STNB was driven by a combination of September rainfall, disease levels and the potential yield of the crop, particularly when the yield potential is very high (p<0.001, R2=60.2%, n=24). However, even low levels of disease at head emergence can produce a significant increase in grain yield.

Grain quality

Spot type net blotch affected grain size (2.5mm screenings) more than other grain characteristics in both likelihood of occurrence and in the magnitude (Table 5). At seventy one per cent of sites (12/17) fungicide application decreased screenings. With fungicide use the median response was to reduce screenings by just over a third, although even higher reductions occur - narrow shaped varieties such as Scope tended to respond more than other varieties (Figure 1). In seven of the 12 responsive sites the reduction in screenings would have allowed the grain to become eligible for a malting/food grade (Figure 1). Sites where spring rainfall was below 80mm were less likely to have a yield or screenings response to STNB control, however in a small number of trials where there had been a dry spring there was a screenings response in the absence of a yield response to fungicide but the likelihood of this was low (18%).

Figure 1. Screenings (%<2.5mm) for untreated and treated (plus fungicide) at sites with available data. The 20% and 35% limits for delivery into Malt1/BFOD1 (20%) and Malt2/BFOD2 (35%) are shown as dotted lines.

Grain weight was significantly improved with fungicide use in 53% of trials, sometimes in the absence of a grain yield response (16%). Hectolitre increased with fungicide use in 35% of trials (Table 5) but a grain yield response was required before this could occur. Grain brightness and protein levels were improved with fungicide use (Table 5). A significant grain yield response was required before an effect on brightness and protein occurred. Hence protein levels decreased with a fungicide use as they were diluted by an increase in grain yield.

Table 5. Grain quality changes with fungicide use shown as averages (n = number of sites with data available). Screenings are %<2.5mm, grain weight (mg, db), hectolitre weight (kg/hL), brightness (NIR L* score), protein (NIR %) shown as values so that screenings is the average reduction in screenings produced.

Quality parameter

Responsive sites (%)

Average response (%)

Average change^

n

Screenings

74%

-49

-14

17

Grain weight

46%

3.4

2.7

13

Hectolitre weight

35%

1

2.1

17

Brightness

42%

0.8

0.9

12

Protein

36%

-3.1

-0.1

14

Effect of fungicide timing

Trials that showed a significant yield response to fungicide applications were mainly from the medium and high rainfall zones. Four of these trials had a single fungicide application (most at stem elongation), four had two (double) applications at stem extension and half head emerged and five compared both single and double fungicide applications, including seed dressing. Table 6 can be used to compare the effectiveness of different fungicide timings within a trial by using the trial %Lsd to determine if the differences between treatments are significant. As an example, at the bottom of the table, the trial at Gibson showed that a seed dressing (fluxapyroxad) provided a 15% yield benefit over the untreated barley but a double foliar fungicide spray at Z31 + Z39 had a 24% yield response which was significantly better than the seed dressing treatments when the 5% lsd for the site is applied.

All of the single stem extension and flag leaf emergence fungicide treatments significantly increased yield compared to untreated barley with responses ranging from 5 – 59% (0.19 – 1.73 t/ha) of the untreated yield.

Table 6. Significant yield responses (% above nil) to fungicides applied to control STNB at various times as a seed dressing (SD), single or double foliar fungicide at the growth stages shown. Fungicide timings are grouped as prior to stem extension (pre Z30), stem extension (Z30-36) or flag emerging (Z37-39). ns=no yield response. Shaded section highlights single versus double fungicide comparisons.

Yield response (% untreated)

Trial

Location name

Nil t/ha

Lsd %

Timing

(single fung)

SD

Pre- Z30

Pre- flag Z30-36

Flag emerg Z37-39

Double

Timing

(double spray)

99ES1

Scaddan

2.63

9

Z33

17

-

99AL5

Wellstead

3.0

10

Z35

24

-

01AL03

South Stirlings

2.94

15

Z37

59

-

00ES29

Gibson

3.9

13

Z39

32

-

15ES13

Wittenoom Hills

4.22

2

-

23

Z31 + Z44/54^

05ES05 TOS1

Salmon Gums

3.73

4

-

5

Z31 + Z55

05ES05 TOS2

Salmon Gums

3.78

3

-

6

Z31 + Z55

05ES06

Scaddan

3.99

5

-

11

Z31 + Z55

15Farm&Gen

Coomalbidgup

5.60

5

Z31

5

12

Z31 + Z50

15CAgStubble

Corrigin

2.24

6#

Z31, Z38

 

9

10

10

Z31 + Z38

09WC39

Meenar

2.53

28

Z32

 

 

37

 

43

Z32 + Z51

03GE06

Yuna

2.6

11

Z39

12

23

Z39 + Z62

15ES39

Coomalbidgup

4.10

8

Z22

 

ns

 

 

9

Z22 + Z31

15ES11

Gibson

4.97

5

SD

15

15

24

SD+Z55;

Z31+ Z39

^Z44/54 indicates the spread of variety growth stages at this site. #Significance level at this site was p<0.08.

Double fungicide applications, with the first made at stem extension, consistently returned a higher yield than single applications (Table 6, Figure 2). Exceptions to the yield response of double sprays occur when there is a dry spring, as occurred at Corrigin and Meenar (15CAgStubble, 15WC39), where a single application was as effective at improving grain yield as a double fungicide application (Figure 2). There was no data to compare the effect of a single versus double fungicide application on screenings changes.

Figure 2. Yield gain (kg/ha) from making a single or double application of fungicide at three sites. * indicates that the difference is significant (p<0.08 in 03GE06).

On the basis of limited trial results, very early applications of fungicide appear unnecessary. Two of the sites where very early tillering applications were made experienced dry springs and had no yield responses to any fungicide treatment.  However, if we consider leaf disease levels, a tillering fungicide at Mingenew in 2006 had no effect on disease levels at head emergence while a fungicide at stem extension had a significantly less disease (data not shown). At Merredin in 2012, a late tillering fungicide lead to slight reductions in STNB levels but didn’t change green leaf area by Z39. At the Coomalbidgup site of 15ES39 (Table 6) a single Z22 fungicide did not increase yield while a Z22 + Z31 double application did.

Fungicide comparisons

Propiconazole was the most widely applied fungicide, then Prosaro. Figure 3 shows how at single and double applications of each, the performance of propiconazole and Prosaro were comparable apart from one site (15CAgStubble Z31+Z38) which is indicated with an asterisk, where Prosaro was significantly better.

Figure 3. Comparison of the yield gain (kg/ha above untreated) achieved using single or double applications of propiconazole or Prosaro to control STNB at four sites at a range of growth stages. Propiconazole and Prosaro rates as shown; propiconazole rate is equivalent to 125 g/ha active ingredient (500 ml/ha in many formulations).* indicates that the difference is significant (p<0.08).

In two product comparison trials, single and double fungicides were applied. A basic return/cost analysis was done to compare products in two trials, CAgStubble (Table 8) and 15Farm&Gen (Table 9). Grain prices used were Malt1 $260/t, Malt2 $240/t, Feed $230/t with EPR of Scope $3.50, La Trobe $4.00. Various product costs for the rates applied are shown below in Table 7 with an application cost of $10/ha. These tables show that there are a broad range of profitable fungicide options available for growers to consider.

Table 7. Fungicides, their active ingredients and costs ($/ha) for the rates shown.

Product

Rate mL/ha

Price $/ha

Active ingredients

Amistar Xtra®

600

23.00

azoxystrobin + cyproconazole

Amistar Xtra

400

15.00

azoxystrobin + cyproconazole

Opera®

500

7.00

pryraclostrobin + epoxiconazole

Opus®

500

10.25

epoxiconazole

Propiconazole

500^

6.50

propiconazole

Prosaro

150

10.50

prothioconazole + tebuconazole

Radial®

420

14.00

azoxystrobin + epoxiconazole

^125 g active ingredient

Table 8. Returns ($/ha) and net gain over untreated ($/ha) for a range of registered products in a 2015 ConsultAg trial at Corrigin (Scope on barley stubble). Letters indicate significant yield differences (p<0.08). Prop = propiconazole.

Fungicides: 

Z31 rate + Z38 rate

Yield (t/ha)

Screenings (%<2.5mm)

Grade

Return ($/ha)

Net gain ($/ha)

Amistar Xtra 400 + Nil

2.43

a

27

Malt2

$565

58

Prosaro 150 x 2

2.44

a

35

Malt2

$557

50

Prosaro150 + Prop 500

2.47

a

43

Feed

$539

32

Amistar Xtra 600 + Prop 500

2.45

a

43

Feed

$535

28

Prop 500 + Nil

2.43

a

42

Feed

$540

33

Nil + Prop 500

2.43

a

39

Feed

$540

32

Nil + Prosaro150

2.4

ab

45

Feed

$533

26

Nil + Radial 420

2.37

ab

44

Feed

$528

20

Prosaro 150 + Nil

2.37

ab

40

Feed

$527

20

Prop 500 x 2

2.29

bc

48

Feed

$499

-8

Nil

2.24

c

45

Feed

$507

Table 9. Returns ($/ha) and net gain over untreated ($/ha) for a range of registered products in a 2015 Farm and General trial at Coomalbidgup (La Trobe following pasture). Letters indicate significant yield differences (p<0.05); pricing based on yield only – all were assumed to be Malt2. Prop = propiconazole.

Fungicides

Z31 rate + Z38 rate

Yield (t/ha)

Return ($/ha)

Net gain ($/ha)

Prop 500 + Opus 500

6.41

abc

$1,475

$154

Prop 500 + Opera 500

6.31

bcd

$1,456

$135

Prop 500 x 2

6.27

bcd

$1,453

$132

Amistar Xtra 400 x 2

6.34

abcd

$1,446

$124

Opera 500 x 2

6.26

bcd

$1,443

$121

Prop 500 + Amistar Xtra 400

6.14

cde

$1,407

$85

Prop 500 + Prosaro150

6.11

def

$1,401

$80

Prosaro 150 x 2

6.08

defg

$1,386

$65

Opus 500 + Nil

5.95

efg

$1,372

$50

Opus 500 x 2

5.92

efg

$1,358

$36

Amistar Xtra 400 + Nil

5.92

efg

$1,371

$49

Opera 500 + Nil

5.83

fg

$1,360

$38

Prosaro 200 + Nil

5.82

gh

$1,349

$28

Prop 500 + Nil

5.81

gh

$1,353

$32

Nil

5.6

h

$1,322

An alternative strategy to foliar fungicides, particularly those applied at tillering, are systemic seed dressings such as fluxapyroxad which reduced severity of STNB in field trials for periods ranging up to head emergence (Figure 4).

Figure 4. STNB disease progress (% top three leaves) in a disease nursery trial of Hindmarsh comparing the persistence of fluxapryroxad seed dressing against a registered foliar fungicide.

Variety comparisons

Trials confirm that variety yield response to the control of STNB is inverse to their resistance rating for STNB. That is, susceptible to very susceptible (SVS) varieties such as Hindmarsh will have a larger response to fungicide than a susceptible (S) variety such as Scope (Figure 5). The variety currently most resistant to STNB, Fathom (feed) showed the least yield loss at a trial in Wittenoom Hills in 2015 (Figure 5).

Figure 5. Yield gain (kg/ha) of a range of varieties to two applications of fungicide (Z31 + Z49) at Wittenoom Hills (barley on barley) in 2015 with the % response shown relative to the untreated. The rating for STNB is below each variety name.

Conclusions

The likelihood of a yield response and improved returns from controlling even low levels of STNB is very good unless there is a dry spring, when it halves. Low spring rainfall increases the risk of having no yield response and reduces the size of the yield response to fungicide applications. This is because low spring rainfall tends to lower the risk of STNB proliferating as well as decreasing crop yield potential. Overall, the crop yield response from fungicide applications tended to increase with growing season rainfall.

Grain quality was improved with fungicide use, particularly grain size (screenings); there were significant screenings responses when spring rainfall was low and occasionally even without significant yield increases. Grain weight, hectolitre and brightness increased while protein decreased as yields rose with fungicide application, which is consistent with other observations (McLean and Hollaway, 2015; Hills and Paynter 2008). In malting varieties improving grain quality is a significant contribution to the profitability of fungicide applications as it increases the chances of meeting malting specifications, primarily through reduced screenings.

Controlling spot type net blotch in medium and high rainfall areas was most profitable with a double spray at stem extension and then again from flag emergence (Z37) to half head emerged (Z55). Exceptions to this were in a dry spring when a single spray from stem extension or later was the most cost effective; growers need to take the spring rainfall outlook into consideration when deciding if a second fungicide is needed after spraying at stem extension. There were few trials in the low rainfall areas that compared fungicide applications and showed a significant yield change; in itself this indicates the caution needed if more than a single fungicide application is being considered in these environments although a low cost choice fungicide could be used instead of a premium product depending upon other diseases present.

Very early STNB control during tillering has few benefits as the disease usually increases back to untreated levels by flag emergence. However any rotation that avoids sowing barley onto barley will prevent an early build-up of disease as side by side trials at Corrigin (barley on barley versus barley on burnt stubble) showed. Where tillering applications are used, to accrue a yield benefit they will almost certainly need a follow-up application, or multiple, to manage later disease development.

There are a very limited variety number of barley varieties with effective STNB resistance; these are reputed to be coming in the next three to five years (Dave Moody, pers comm) but currently the feed variety Fathom (rated MRMS) is the only one. Fathom was competitive with Hindmarsh (yielding the same or better) in 43% of trials over 2010-2014 (Paynter et al, 2015) and may be a profitable alternative for some growers.

The choice of fungicide to control STNB will depend in part upon what other diseases may be present; this study and others have shown that a range of registered active ingredients are effective against STNB (e.g. Jayasena et al, 2002). In comparisons of the two most commonly applied fungicides, propiconazole and Prosaro, their relative yield gain in crops that are dominated by STNB was comparable in seven out of eight cases. Differences in disease control have been seen between products in higher rainfall environments with wet springs and other disease challenges, such as leaf rust, scald, powdery mildew, where there may be a benefit through the use of a product with best efficacy across a range of diseases. Information on registered foliar fungicides is available from the DAFWA website https://www.agric.wa.gov.au/barley/registered-foliar-fungicides-cereals-western-australia-wa

The seed dressing fluxapyroxad offers an alternative strategy to control a number of diseases, including STNB and may have a role in continuous barley rotations or in other situations where early sustained control is required. Fluxapryroxad has the additional benefit of being a SDHI type fungicide rather than the common DMI (triazole) or a QoL (strobilurin); STNB is considered at medium risk of developing fungicide resistance (FRAC, 2014) and diversifying fungicide group use will help prevent its development. If barley is sown at 70kg/ha, the current cost of fluxapyroxad is approximately $24/ha.

References

Fungicide Resistance Action Committee (FRAC) Pathogen risk list Dec 2014 available from; http://www.frac.info/docs/default-source/publications/pathogen-risk/pathogen-risk-list.pdf?sfvrsn=8

Hills AL and Paynter BH (2008) Barley agronomy highlights: canopy management. Agribusiness Crop Updates, Department of Agriculture and Food Western Australia, Perth, 2008

Jayasena KW, Loughman R and Majewski J (2002) Evaluation of fungicides in control of spot-type net blotch on barley. Crop Protection 21: 63-69

McLean MS and Hollaway GJ (2015) Spot form of net blotch yield loss and management in barley using fungicides and resistance in Victoria GRDC Crop Updates Victoria

Paynter BH, Trainor GC, Gupta S, Collins S and Dhammu H (2015) 2016 Barley variety sowing guide. Department of Agriculture and Food Western Australia Bulletin 4866.

VSN International (2014) GenStat for Windows 17th Edition. VSN Inernational, Hemel Hempstead, UK

Key words

Barley, spot type net blotch, Pyrenophora teres f. maculata, grain yield

Acknowledgments

We acknowledge the technical input of Jason Bradley, Kazue Tanaka, Stuart Vincent, Alastair Hall, Anne Smith and Sue Cartledge. DAFWA’s research support units at Esperance, Katanning, Northam, Merredin, Geraldton, Mt Barker and Avon sowed, managed and harvested DAFWA trials. Living Farm for management of the ConsultAg Corrigin site; Kalyx for management of the Bayer Meenar site. Thanks to Andrew van Burgel for statistical advice.The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support.

GRDC Project Number: DAW00229

Paper reviewed by:

® Registered trademark

*     Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.

Disclaimer: Mention of trade names does not imply endorsement or preference of any company’s product by Department of Agriculture and Food, Western Australia. Only registered fungicide products are recommended. When choosing fungicides, consider the range of diseases that threaten your crop. Consult product labels for registrations. Read and follow directions on fungicide labels carefully.

GRDC Project Code: GIA00004,