Recent experiences with triazole fungicide use for Septoria leaf ...

EPPO Workshop
Recent Experiences with
Triazole Fungicide use
for Septoria control on Winter
Wheat in Ireland
Dr Tom McCabe
School of Agriculture
University College Dublin

Topics Covered
Update on Septoria resistance monitoring in Ireland
Brief review of fungicide practices in recent years
Role of chlorothalonil
Triazole use strategy trial data on use alone versus use in
mixtures
Role of carboxamide chemistry
Fungicide strategies on wheat into the future and key factors
influencing usage on farm

The emergence of Septoria tritici resistance to
strobilurin fungicides was stunning and dramatic
In Ireland 2002 was the highest disease pressure year in at
least a decade
disease control on wheat started very well and finished very
variably
high spend on strobilurin-based fungicide programmes with
over 90% of crops receiving F500 at mid-season
uneven control of Septoria across fields e.g. disease buildup in
a very unusual spatial pattern
unexplained differences in efficacy of disease control between
fields, farms, localities, regions

Triazole Resistance Monitoring in Ireland
Teagasc monitoring of tebuconazole and metconazole
showed shifts in 2004 and 2005 and no clear shifts
since then
The R5a and R6/R7 mutations dominating the population
In 2008 and 2009 monitoring strains found with
reduced sensitivity to epoxiconazole and
prothioconazole
New mutation detected (S524T) in autumn 08 and spring 09 at low
levels
Teagasc recommended restrictions on use of prothio
and epoxi until more information on triazole use in the
field became available

Disease Control Programmes on Wheat in Ireland
Since 2003 to date increased dependency on triazole
fungicide use
High usage of chlorothalonil T1 and T2
T zero on early-sown crops (triazole-based)
Introduction of boscalid as useful triazole partner
fungicides into spray programmes mainly at T2
T3 is a key fungicide treatment ear blight control
Relatively robust doses across the programme as high
disease pressure in many seasons and high yield response
expectation (2.5 4 t/ha)

Rainfall (mm/day) UCD LYONS Summer 2008
May JuneTime (days) July
20
15
10

% Septoria Infection
75
50
25
0
CTL +/- Triazole for Leaf 3 Septoria Control
Average 2 years
No Triazole Triazole
UNT BRAVO 0.5 BRAVO 1.0 BRAVO 1.5 BRAVO 2.0

Grain Yield (t/ha)
11
10
9
8
7
6
CTL +/- Triazole for Grain Yield Response
2007 Trial
No Triazole Triazole
UNT BRAVO 0.5 BRAVO 1.0 BRAVO 1.5 BRAVO 2.0

Grain Yield Data for CTL (avg two years)
BRAVO 2.0
BRAVO 1.5
BRAVO 1.0
BRAVO 0.5
UNT
-0.25 0 0.25 0.5 0.75 1 1.25
Grain Yield (t/ha)

Conclusions on CTL + Triazole
CTL showed improved efficacy as the dose rate increased
Grain yield responses observed to higher dose CTL
applications
Consistent yield response to Epoxi use in both years,
large yield increment in year 2 (2 t/ha)
In Ireland CTL is a key part of the fungicide programme
with two applications expected
evidence of reduced triazole curativity when chlorothalonil
mixtures are used 7-10 days curative
The benefit of chlorothalonil is in enhancing the
persistance of disease control. This effect is most
apparent four-six weeks after application

Triazole Choice for Disease Control on Wheat
Prothioconazole and Epoxiconazole are the triazoles
of choice
Rate Flexibilty / Efficacy / Persistence
Both are central to the disease control programme
Mixture strategy is increasingly more important
Favoured mixing partners are tebuconazole and
metconazole
Prosaro and Brutus
Alternating / Sequencing / Restrictions

Practical Disease Management
Triazole Use Strategy

Rainfall (mm)
Rainfall (mm/day) UCD LYONS Summer 2009
May JuneTime (days) July
20
15
10

Prothio v Prothio + Teb
Triazole Studies 2009

% Infection
25
20
15
10
5
0
Disease Control from Mid-Season Fungicide
Wave Timing Studies– cv. Cordiale 2009 (UCD Lyons)
Untr Prothio Prothio+Tebu Epoxi+Boscalid
Early Flag Leaf (24/5) Flag Leaf (30/5) Late Flag Leaf (4/6)
CURATIVE CONTROL : % infection on leaf 3 on 1 st July

% Infection
Disease Control from Mid-Season Fungicide
Wave Timing Studies– cv. Cordiale 2009 (UCD Lyons)
100
75
50
25
0
Untr Prothio Prothio+Tebu Epoxi+Boscalid
Leaf 2 7th July Leaf 2 16th July Leaf 2 23rd July
24 th May Treatment : % infection on leaf 2 on Three Dates

% EFFICACY - 40-45 DAA
100
80
60
40
20
0
Five High Disease Pressure WW Trials in 2009
Epoxi v Epoxi + Metcon Comparison
Untreated Epoxi Epoxi+Metcon
Rath T1 RTN 2 SP RTN 1 SP NEW 2 SP RTN 39 Curative
% Efficacy – 40 to 45 days after application

Fungicide Use Strategies on Wheat in 2009 / 2010
Principles of Integrated Crop Management – Cultivar / Weather
/ Disease / Fungicide Use
Fungicide Use – Mixtures – key role for chlorothalonil, also
clear benefit from triazole mixtures (data 2003-2009)
Use of specific triazole a.i.’s once / twice ?? – very much
secondary issue, should be flexible based on risk of other
diseases e.g. eyespot, ear fusarium risk at T3 , yellow rust etc
Field performance is the key factor
- need to produce high yield and quality in a very difficult
production scenario
- closely monitor field efficacy across sites and seasons

Fungicide Use and Disease Control on Wheat in 2010
Lower disease pressure with fewer infection periods and
modest yield responses (1 – 2 t/ha)
Epoxi and Prothio showed similar good efficacy across
range of trial sites and cultivars
Triazole mixture benefits – evident in disease control but
less apparent in yield response than in previous years
Chlorothalonil benefits as previously described
Carboxamide

Role of new Carboxamide Chemistry
Good performance in mixtures for disease control, GLA, yield
response (< in 2010), yield benefits of 0.5 t/ha +
Good potential but in partnership with existing chemistry
- formulation will be a key issue
- partner product is also critical
- uncertainty about optimum timing
- use once / twice ?
resistance risk – well integrated programmes will be v
important, use of triazole + CTL + carboxamide ?

Practical Disease Management – Key factors
influencing fungicide use on farm
IPM - good integrated disease control practices
Winter Wheat v Spring Wheat ?
Cultivar (Riband / Consort)
Rotation / Sowing date / Seedrate /
N nutrition
Cost : Benefit – big factor here is the grain price expectation ,
2007 / 2010 poor advice
Focus on efficacy of the fungicide treatment
Well timed triazole-based fungicide treatments with mixture
strategy at each timing and fungicide loading options

Fungicide Resistance Issues
& Irish Climate
Sustainable resistance management
- must achieve effective fungal disease management
- need a number of fungicide mode of actions on each crop and
for each target pest
- uncertain of future needs
Season long disease control – unique requirements
- is the use of less than four modes of action to be considered
extremely risky and unsustainable
- need diversity in available modes of action including
genuinely multi-site chemicals