Early fungicide application can be profitable for
Managing Yellow spot and Stagonospora Nodorum
in Wheat-on-Wheat cropping
Ciara Beard and Anne Smith, Department of Agriculture and Food
KEY MESSAGES
•
Foliar fungicide applications at or prior to first node stage (Z31) can be effective at controlling
leaf spot diseases in susceptible wheat varieties under high disease pressure. In six out of eight trials
in 2010 and 2011 yields were increased (on average 11% above untreated) and grain quality
improved. The most reliable timing for early foliar fungicide application was at the first node stage.
•
Applications prior to the first node stage (e.g. seedling and tillering stage) reduced early
infection, but often gave a shorter duration of disease protection and were less likely to be as
profitable as applications at the first node stage.
•
Two in-furrow fungicide active ingredients were tested and provided early disease control and
performed well in conjunction with a Z39 foliar spray to give yield benefits similar to early foliar
applications.
AIMS
High levels of yellow spot or stagonospora (septoria) nodorum blotch before flag leaf emergence can
reduce plant growth and ultimately the yield of susceptible wheat varieties. To avoid possible disease
damage, many growers apply foliar fungicides at early growth stages, from five-leaf stage (Z15) to first
node (Z31), while they are ‘going over the paddock’ applying herbicides. Our research aims were to
determine if foliar fungicide application prior to stem extension can be valuable for controlling early
infection and, more importantly, profitable by giving a yield benefit across a range of environments.
We also investigated some new fungicide active ingredients as in-furrow applications to assess the
disease control and yield benefits of this application technology. Currently there are no seed dressings
or in-furrow fungicides registered in WA for the control of wheat leaf spot diseases.
METHOD
A series of eight similar trials in 2010 and 2011 in the central and northern wheatbelt were carried out
to determine which timing of early foliar applications gives the best leaf spot disease control and yield
benefit. All trials were sown on to wheat stubble and used varieties susceptible to yellow spot or
stagonospora nodorum.
Six trials were sown by cone-seeder and two were opportunistically established in farmer’s paddocks.
Fertilisers and herbicides were applied as necessary. Fungicides (either Prosaro® or Tilt®) were applied
in 80 L water by boom. Rainfall was monitored with an electronic rain gauge at each site where
possible.
Treatments – Sown trials
All trials used a randomised block design (latinised) with all treatments replicated 4 times. Plot size
was 20m x 1.8m with a barley buffer between wheat plots. In 2010 the following treatments were
applied at three sites – Eradu (EGA Eagle Rock), Mingenew (EGA Bonnie Rock) and Northam
(Tammarin Rock):
1. Untreated
2. Prosaro® @ 150 mL/ha at Z15 and follow up spray Prosaro® @ 300 mL/ha at Z39
3. Prosaro® @ 150 mL/ha at Z25 and follow up spray Prosaro® @ 300 mL/ha at Z39
4. Prosaro® @ 150 mL/ha at Z31 and follow up spray Prosaro® @ 300 mL/ha at Z39
5. Prosaro® @ 300 mL/ha at Z15
6. Prosaro® @ 300 mL/ha at Z31
7. Prosaro® @ 300 mL/ha at Z39
8. Full control – Four fungicide sprays to assess site yield potential
In 2011 these treatments were also applied at three additional sites - Eradu (EGA Eagle Rock), Mingenew
(Mace) and Cunderdin (Yitpi) however, in these trials, the second (Z39) spray on treatments 2, 3 and 4 was
150 mL/ha Prosaro®. At the Eradu and Mingenew sites there were also four additional treatments - two infurrow products with or without follow up foliar fungicide applications at Z39. The two in-furrow fungicide
active ingredients tested are not named as they are not currently registered for this use in WA.
Treatments – Opportunistic trials
In 2011, trials were established within growers’ paddocks at two locations in the northern wheatbelt, Nangetty
and Yuna. The trials had a randomised block design (each plot was 20 m x 5m) with four replicates of the
following treatments at each site: 1. Unsprayed, 2. Sprayed at Z30 (when grower sprayed), 3. Sprayed at Z30
+ follow up spray at Z39/41, 4. Sprayed at Z39/41, 5. Full control (fungicide at high rate applied at Z30, Z39
and Z55).
Measurements
Plant emergence counts were conducted on all sown plots 3-5 weeks after sowing. Necrotic leaf area was
determined on top 3 to 4 leaves (on 15 tillers /plot) from all plots at Z15, Z25, Z31, Z39, Z55 (i.e. before each
foliar fungicide spray) and Z72, or in the case of opportunistic trials assessed at regular intervals after trial
establishment. Pathogen identification as either yellow spot or stagonospora nodorum was confirmed through
AGWEST Plant Labs at two times during the season. Trials were harvested and a grain sample from each
plot weighed and sub-sampled for grain quality (protein, hectolitre weight, grain sievings and thousand-grain
weight).
RESULTS AND DISCUSSION
Early fungicide sprays
This research has found that when conditions favour early season disease (for example, susceptible wheat
variety sown on wheat stubble following good opening rains), spraying for yellow spot and stagonospora
(septoria) nodorum prior to stem extension can be economical (example trial result shown in Figure 1).
Yield (t/ha)
70
Flag-1 area diseased
60
2.50
$135
Yield (t/ha)
2.00
$96
$128
$93
$117
$115
50
40
1.50
30
1.00
20
0.50
10
0.00
Leaf area diseased (Flag-1)
3.00
0
Untreated
Prosaro
Prosaro
Prosaro
Prosaro
Prosaro
Prosaro
Full control
150mL@Z15 150mL@Z25 150mL@Z31 300mL@Z15 300mL@Z31 300mL@Z39
300mL@Z39 300mL@Z39 300mL@Z39
Figure 1. Early fungicide applications reduced disease and increased yield on EGA Eagle Rock grown on
wheat stubble at Eradu in 2010.
For each trial in which a single application at seedling / tillering stage (Z15-25) gave a significant yield
benefit, a similar or greater benefit was achieved with a single application at stem extension (Z31). The yield
penalty for delaying application until Z31 was found to be minimal across all trials so, on the whole, the Z31
timing was found to be the best for added length of crop protection.
In four out of the eight trials conducted, fungicide application at Z31 with a follow up spray at Z39 was the
most profitable treatment (or equal best in one case). In two of the eight trials a single fungicide application at
Z31 was the most profitable treatment (Table 1). On average across all eight trials the Z31 +Z39 double
spray strategy was the most profitable giving on average a profit of $109 above untreated.
Table 1. Summary of treatment results from eight trials* conducted over during 2010-2011
Fungicide Treatment
Average yield increase
above untreated (t/ha)
Average profit
# above
untreated
0.2
0.3
0.3
0.3
0.5
57
75
57
56
109
Single spray Z15 or Z25
Single spray Z31
Single spray Z41
Double spray Z15/Z25 and Z39
Double spray Z31 and Z39
* Results from Northam 2010 trial not included as grain yields were poor due to drought and did not respond to fungicide application
# Profit depended on fungicide product and rate used. Wheat price used in 2011= $270/t, in 2010 = $313/t. Cost of fungicide application =
$8/ha, Fungicide : Prosaro® at 300 mL/ha = $19.80, Tilt® at 500 mL/ha = $9.
Fungicide responses are a result of the disease being present and a favourable environment to allow disease
progression throughout the season. In some years there was insufficient disease at Z39 or insufficient rain
after this growth stage, to make a flag leaf application profitable (Table 2). For example, in 2010, early
application of foliar fungicide was profitable at both Eradu and Mingenew where yellow spot and
stagonospora nodorum developed to moderate levels. While a flag leaf spray (at Z39) was profitable at Eradu
(where 97 mm of rain fell in the eight weeks after Z39), it was not profitable at Mingenew which had a dry
spring (only 64 mm of rain fell at the site after Z39). In some situations, such as Northam in 2010, no
fungicide applications increased profit due to drought conditions which did not allow foliar diseases to
develop or the crop to yield adequately. Conversely, at Cunderdin in 2011, disease levels were low or
moderate prior to stem extension with no profit from application at these times, however favourable
conditions, particularly after flag leaf emergence resulted in positive responses to later spray application
timings.
Table 2. Summary of eight trials conducted during 2010-2011.
Location
and Year
Variety
Disease
without
fungicide
control
(Average leaf
area diseased
on top 3 leaves)
Z25/30
Z65/69
Disease
Fungicide
timings
increasing
yield
Rain
during 8
weeks
after Z39
Notes on season
Above average rainfall growing
season, lots of regular falls July
and August
One heavy downpour end of may
(54mm), Sept only two large falls
(18mm each)
Lots of regular small falls (and a
few large) throughout season
favoured ongoing disease
One heavy downpour end of may
(54mm), Sept only two large falls
(18mm each)
Low levels of disease and very
little disease response to
fungicide through year but with
very good rain during grain fill
Below average rainfall. Dry June,
July and September
Eradu,
2011
Eagle
Rock
13
50
YS &
SNB
All
98
Mingenew,
2011
Mace
5
45
YS &
SNB
All
130
Yuna*,
2011
Mace
6
38
YS
dominant
Z41
79
Nangetty*,
2011
Calingiri
7
40
YS &
SNB
Z31+41, Z41
130
(estimate)
Cunderdin,
2011
Yitpi
11
43
YS
dominant
All except Z14
96
Eradu,
2010
Mingenew,
2010
Eagle
Rock
Bonnie
Rock
19
36
All
97
10
29
Z32, Z25+Z41,
Z32+41
64
Dry June and September
Northam,
2010
Tammarin Rock
2
21
n/a
25
Reasonable July rainfall, but
drought during Aug-Oct, No yield
responses were evident
YS &
SNB
SNB
dominant
YS
dominant
* Opportunistic trials in which the earliest fungicide application was Z30
In-furrow fungicide treatments
The in-furrow fungicides tested, performed similarly to a single foliar fungicide at Z15 or Z31 and when
used in conjunction with a Z39 foliar fungicide spray gave similar yield results to the 2 spray
treatments. At Eradu in 2011, where yellow spot dominated, both of the in-furrow fungicides
significantly reduced disease until the last disease assessment at Z69 which resulted in significant
yield increases above the untreated (Figure 2). The same was true at Mingenew in 2011, where
stagonospora nodorum was dominant for much of the season.
5
Yield (t/ha)
4
3
2
1
0
Untreated
Prosaro @ Z15
Prosaro @ Z31
Product A
in-furrow
Product B
in-furrow
Product A
in-furrow &
Prosaro @ Z39
Product B
in-furrow &
Prosaro @ Z39
Full Control - 4
fungicide sprays
Figure 2. Yield, of fungicide treatments applied to EGA Eagle Rock at Eradu in 2011.
CONCLUSION
When a wheat variety susceptible to yellow spot and/or stagonospora (septoria) nodorum blotch is
grown on wheat stubble, onset of these diseases prior to stem extension is likely to occur in most
seasons. These trials have shown that fungicide applications applied at or before stem extension
(Z31) can be effective and provide positive economic returns when disease pressures are moderate to
high.
Disease development and fungicide response is determined by the presence of the disease in the
crop and the occurrence of disease favourable conditions following application. Therefore in the
presence of early season disease pressure and continuing favourable conditions, applications prior to
stem extension are more likely to be effective. Similarly, flag leaf applications are more likely to be
effective when weather conditions favour development of disease after application and during grain
filling.
Application of foliar fungicides at seedling or tillering growth stages will not provide economic benefit if
disease is not present or not developing at the time of application. Fungicide application before Z31
can be justified when disease is intense at these stages, however this research has shown that in
most cases it can be more profitable to delay application until Z31. A follow up spray at Z39 is likely to
be profitable and provide additional yield response if disease development continues towards the flag
leaf and at least 80 mm of rainfall is expected in the eight weeks after Z39.
The in-furrow fungicides tested show promise for leaf spot disease control and in the future they may
become an alternative to foliar applications, for the control of early season leaf spot infections.
KEY WORDS
Yellow spot, Fungicide, Wheat, Disease
ACKNOWLEDGMENTS
GRDC for funding the research, DAFWA Geraldton Research Support Unit for seeding and harvesting
trials. Mingenew Irwin Group and the grain growers, Clancy Michael, Randal Levett, Greg Creasy,
Ashley Eastough, Andrew Messina, for hosting trials.
GRDC Project No.:
DAW00210
Paper reviewed by:
Geoff Thomas and Bill MacLeod